Index: head/en_US.ISO8859-1/books/handbook/Makefile =================================================================== --- head/en_US.ISO8859-1/books/handbook/Makefile (revision 45601) +++ head/en_US.ISO8859-1/books/handbook/Makefile (revision 45602) @@ -1,317 +1,318 @@ # # $FreeBSD$ # # Build the FreeBSD Handbook. # # ------------------------------------------------------------------------ # To add a new chapter to the Handbook: # # - Update this Makefile, chapters.ent and book.xml # - Add a descriptive entry for the new chapter in preface/preface.xml # # ------------------------------------------------------------------------ .PATH: ${.CURDIR}/../../share/xml/glossary MAINTAINER= doc@FreeBSD.org DOC?= book FORMATS?= html-split INSTALL_COMPRESSED?= gz INSTALL_ONLY_COMPRESSED?= IMAGES_EN = advanced-networking/isdn-bus.eps IMAGES_EN+= advanced-networking/isdn-twisted-pair.eps IMAGES_EN+= advanced-networking/natd.eps IMAGES_EN+= advanced-networking/net-routing.pic IMAGES_EN+= advanced-networking/pxe-nfs.png IMAGES_EN+= advanced-networking/static-routes.pic IMAGES_EN+= bsdinstall/bsdinstall-adduser1.png IMAGES_EN+= bsdinstall/bsdinstall-adduser2.png IMAGES_EN+= bsdinstall/bsdinstall-adduser3.png IMAGES_EN+= bsdinstall/bsdinstall-boot-loader-menu.png IMAGES_EN+= bsdinstall/bsdinstall-boot-options-menu.png IMAGES_EN+= bsdinstall/bsdinstall-newboot-loader-menu.png IMAGES_EN+= bsdinstall/bsdinstall-choose-mode.png IMAGES_EN+= bsdinstall/bsdinstall-config-components.png IMAGES_EN+= bsdinstall/bsdinstall-config-hostname.png IMAGES_EN+= bsdinstall/bsdinstall-config-keymap.png IMAGES_EN+= bsdinstall/bsdinstall-config-services.png IMAGES_EN+= bsdinstall/bsdinstall-config-crashdump.png IMAGES_EN+= bsdinstall/bsdinstall-configure-network-interface-ipv4-dhcp.png IMAGES_EN+= bsdinstall/bsdinstall-configure-network-interface-ipv4.png IMAGES_EN+= bsdinstall/bsdinstall-configure-network-interface-ipv4-static.png IMAGES_EN+= bsdinstall/bsdinstall-configure-network-interface-ipv6.png IMAGES_EN+= bsdinstall/bsdinstall-configure-network-interface-ipv6-static.png IMAGES_EN+= bsdinstall/bsdinstall-configure-network-interface-slaac.png IMAGES_EN+= bsdinstall/bsdinstall-configure-network-interface.png IMAGES_EN+= bsdinstall/bsdinstall-configure-network-ipv4-dns.png IMAGES_EN+= bsdinstall/bsdinstall-configure-wireless-accesspoints.png IMAGES_EN+= bsdinstall/bsdinstall-configure-wireless-scan.png IMAGES_EN+= bsdinstall/bsdinstall-configure-wireless-wpa2setup.png IMAGES_EN+= bsdinstall/bsdinstall-distfile-extracting.png IMAGES_EN+= bsdinstall/bsdinstall-distfile-fetching.png IMAGES_EN+= bsdinstall/bsdinstall-distfile-verifying.png IMAGES_EN+= bsdinstall/bsdinstall-final-confirmation.png IMAGES_EN+= bsdinstall/bsdinstall-finalconfiguration.png IMAGES_EN+= bsdinstall/bsdinstall-final-modification-shell.png IMAGES_EN+= bsdinstall/bsdinstall-keymap-10.png IMAGES_EN+= bsdinstall/bsdinstall-keymap-select-default.png IMAGES_EN+= bsdinstall/bsdinstall-mainexit.png IMAGES_EN+= bsdinstall/bsdinstall-netinstall-files.png IMAGES_EN+= bsdinstall/bsdinstall-netinstall-mirrorselect.png IMAGES_EN+= bsdinstall/bsdinstall-part-entire-part.png IMAGES_EN+= bsdinstall/bsdinstall-part-guided-disk.png IMAGES_EN+= bsdinstall/bsdinstall-part-guided-manual.png IMAGES_EN+= bsdinstall/bsdinstall-part-manual-addpart.png IMAGES_EN+= bsdinstall/bsdinstall-part-manual-create.png IMAGES_EN+= bsdinstall/bsdinstall-part-manual-partscheme.png IMAGES_EN+= bsdinstall/bsdinstall-part-review.png IMAGES_EN+= bsdinstall/bsdinstall-post-root-passwd.png IMAGES_EN+= bsdinstall/bsdinstall-set-clock-local-utc.png IMAGES_EN+= bsdinstall/bsdinstall-timezone-confirm.png IMAGES_EN+= bsdinstall/bsdinstall-timezone-country.png IMAGES_EN+= bsdinstall/bsdinstall-timezone-region.png IMAGES_EN+= bsdinstall/bsdinstall-timezone-zone.png IMAGES_EN+= bsdinstall/bsdinstall-zfs-disk_info.png IMAGES_EN+= bsdinstall/bsdinstall-zfs-disk_select.png IMAGES_EN+= bsdinstall/bsdinstall-zfs-geli_password.png IMAGES_EN+= bsdinstall/bsdinstall-zfs-menu.png IMAGES_EN+= bsdinstall/bsdinstall-zfs-partmenu.png IMAGES_EN+= bsdinstall/bsdinstall-zfs-vdev_invalid.png IMAGES_EN+= bsdinstall/bsdinstall-zfs-vdev_type.png IMAGES_EN+= bsdinstall/bsdinstall-zfs-warning.png IMAGES_EN+= geom/striping.pic IMAGES_EN+= install/adduser1.scr IMAGES_EN+= install/adduser2.scr IMAGES_EN+= install/adduser3.scr IMAGES_EN+= install/boot-loader-menu.scr IMAGES_EN+= install/boot-mgr.scr IMAGES_EN+= install/config-country.scr IMAGES_EN+= install/config-keymap.scr IMAGES_EN+= install/console-saver1.scr IMAGES_EN+= install/console-saver2.scr IMAGES_EN+= install/console-saver3.scr IMAGES_EN+= install/console-saver4.scr IMAGES_EN+= install/disklabel-auto.scr IMAGES_EN+= install/disklabel-ed1.scr IMAGES_EN+= install/disklabel-ed2.scr IMAGES_EN+= install/disklabel-fs.scr IMAGES_EN+= install/disklabel-root1.scr IMAGES_EN+= install/disklabel-root2.scr IMAGES_EN+= install/disklabel-root3.scr IMAGES_EN+= install/disk-layout.eps IMAGES_EN+= install/dist-set.scr IMAGES_EN+= install/dist-set2.scr IMAGES_EN+= install/docmenu1.scr IMAGES_EN+= install/ed0-conf.scr IMAGES_EN+= install/ed0-conf2.scr IMAGES_EN+= install/edit-inetd-conf.scr IMAGES_EN+= install/fdisk-drive1.scr IMAGES_EN+= install/fdisk-drive2.scr IMAGES_EN+= install/fdisk-edit1.scr IMAGES_EN+= install/fdisk-edit2.scr IMAGES_EN+= install/ftp-anon1.scr IMAGES_EN+= install/ftp-anon2.scr IMAGES_EN+= install/hdwrconf.scr IMAGES_EN+= install/keymap.scr IMAGES_EN+= install/main1.scr IMAGES_EN+= install/mainexit.scr IMAGES_EN+= install/main-std.scr IMAGES_EN+= install/main-options.scr IMAGES_EN+= install/main-doc.scr IMAGES_EN+= install/main-keymap.scr IMAGES_EN+= install/media.scr IMAGES_EN+= install/mouse1.scr IMAGES_EN+= install/mouse2.scr IMAGES_EN+= install/mouse3.scr IMAGES_EN+= install/mouse4.scr IMAGES_EN+= install/mouse5.scr IMAGES_EN+= install/mouse6.scr IMAGES_EN+= install/mta-main.scr IMAGES_EN+= install/net-config-menu1.scr IMAGES_EN+= install/net-config-menu2.scr IMAGES_EN+= install/nfs-server-edit.scr IMAGES_EN+= install/ntp-config.scr IMAGES_EN+= install/options.scr IMAGES_EN+= install/pkg-cat.scr IMAGES_EN+= install/pkg-confirm.scr IMAGES_EN+= install/pkg-install.scr IMAGES_EN+= install/pkg-sel.scr IMAGES_EN+= install/probstart.scr IMAGES_EN+= install/routed.scr IMAGES_EN+= install/security.scr IMAGES_EN+= install/sysinstall-exit.scr IMAGES_EN+= install/timezone1.scr IMAGES_EN+= install/timezone2.scr IMAGES_EN+= install/timezone3.scr IMAGES_EN+= install/userconfig.scr IMAGES_EN+= install/userconfig2.scr IMAGES_EN+= mail/mutt1.scr IMAGES_EN+= mail/mutt2.scr IMAGES_EN+= mail/mutt3.scr IMAGES_EN+= mail/pine1.scr IMAGES_EN+= mail/pine2.scr IMAGES_EN+= mail/pine3.scr IMAGES_EN+= mail/pine4.scr IMAGES_EN+= mail/pine5.scr IMAGES_EN+= install/example-dir1.eps IMAGES_EN+= install/example-dir2.eps IMAGES_EN+= install/example-dir3.eps IMAGES_EN+= install/example-dir4.eps IMAGES_EN+= install/example-dir5.eps IMAGES_EN+= security/ipsec-network.pic IMAGES_EN+= security/ipsec-crypt-pkt.pic IMAGES_EN+= security/ipsec-encap-pkt.pic IMAGES_EN+= security/ipsec-out-pkt.pic IMAGES_EN+= virtualization/parallels-freebsd1.png IMAGES_EN+= virtualization/parallels-freebsd2.png IMAGES_EN+= virtualization/parallels-freebsd3.png IMAGES_EN+= virtualization/parallels-freebsd4.png IMAGES_EN+= virtualization/parallels-freebsd5.png IMAGES_EN+= virtualization/parallels-freebsd6.png IMAGES_EN+= virtualization/parallels-freebsd7.png IMAGES_EN+= virtualization/parallels-freebsd8.png IMAGES_EN+= virtualization/parallels-freebsd9.png IMAGES_EN+= virtualization/parallels-freebsd10.png IMAGES_EN+= virtualization/parallels-freebsd11.png IMAGES_EN+= virtualization/parallels-freebsd12.png IMAGES_EN+= virtualization/parallels-freebsd13.png IMAGES_EN+= virtualization/virtualpc-freebsd1.png IMAGES_EN+= virtualization/virtualpc-freebsd2.png IMAGES_EN+= virtualization/virtualpc-freebsd3.png IMAGES_EN+= virtualization/virtualpc-freebsd4.png IMAGES_EN+= virtualization/virtualpc-freebsd5.png IMAGES_EN+= virtualization/virtualpc-freebsd6.png IMAGES_EN+= virtualization/virtualpc-freebsd7.png IMAGES_EN+= virtualization/virtualpc-freebsd8.png IMAGES_EN+= virtualization/virtualpc-freebsd9.png IMAGES_EN+= virtualization/virtualpc-freebsd10.png IMAGES_EN+= virtualization/virtualpc-freebsd11.png IMAGES_EN+= virtualization/virtualpc-freebsd12.png IMAGES_EN+= virtualization/virtualpc-freebsd13.png IMAGES_EN+= virtualization/vmware-freebsd01.png IMAGES_EN+= virtualization/vmware-freebsd02.png IMAGES_EN+= virtualization/vmware-freebsd03.png IMAGES_EN+= virtualization/vmware-freebsd04.png IMAGES_EN+= virtualization/vmware-freebsd05.png IMAGES_EN+= virtualization/vmware-freebsd06.png IMAGES_EN+= virtualization/vmware-freebsd07.png IMAGES_EN+= virtualization/vmware-freebsd08.png IMAGES_EN+= virtualization/vmware-freebsd09.png IMAGES_EN+= virtualization/vmware-freebsd10.png IMAGES_EN+= virtualization/vmware-freebsd11.png IMAGES_EN+= virtualization/vmware-freebsd12.png # Images from the cross-document image library IMAGES_LIB= callouts/1.png IMAGES_LIB+= callouts/2.png IMAGES_LIB+= callouts/3.png IMAGES_LIB+= callouts/4.png IMAGES_LIB+= callouts/5.png IMAGES_LIB+= callouts/6.png IMAGES_LIB+= callouts/7.png IMAGES_LIB+= callouts/8.png IMAGES_LIB+= callouts/9.png IMAGES_LIB+= callouts/10.png IMAGES_LIB+= callouts/11.png IMAGES_LIB+= callouts/12.png IMAGES_LIB+= callouts/13.png IMAGES_LIB+= callouts/14.png IMAGES_LIB+= callouts/15.png # # SRCS lists the individual XML files that make up the document. Changes # to any of these files will force a rebuild # # XML content SRCS+= audit/chapter.xml SRCS+= book.xml SRCS+= bsdinstall/chapter.xml SRCS+= colophon.xml SRCS+= dtrace/chapter.xml SRCS+= advanced-networking/chapter.xml SRCS+= basics/chapter.xml SRCS+= bibliography/chapter.xml SRCS+= boot/chapter.xml SRCS+= config/chapter.xml SRCS+= cutting-edge/chapter.xml SRCS+= desktop/chapter.xml SRCS+= disks/chapter.xml SRCS+= eresources/chapter.xml SRCS+= firewalls/chapter.xml +SRCS+= zfs/chapter.xml SRCS+= filesystems/chapter.xml SRCS+= geom/chapter.xml SRCS+= install/chapter.xml SRCS+= introduction/chapter.xml SRCS+= jails/chapter.xml SRCS+= kernelconfig/chapter.xml SRCS+= l10n/chapter.xml SRCS+= linuxemu/chapter.xml SRCS+= mac/chapter.xml SRCS+= mail/chapter.xml SRCS+= mirrors/chapter.xml SRCS+= multimedia/chapter.xml SRCS+= network-servers/chapter.xml SRCS+= pgpkeys/chapter.xml SRCS+= ports/chapter.xml SRCS+= ppp-and-slip/chapter.xml SRCS+= preface/preface.xml SRCS+= printing/chapter.xml SRCS+= security/chapter.xml SRCS+= serialcomms/chapter.xml SRCS+= virtualization/chapter.xml SRCS+= x11/chapter.xml # Entities SRCS+= chapters.ent SYMLINKS= ${DESTDIR} index.html handbook.html # Turn on all the chapters. CHAPTERS?= ${SRCS:M*chapter.xml} XMLFLAGS+= ${CHAPTERS:S/\/chapter.xml//:S/^/-i chap./} XMLFLAGS+= -i chap.freebsd-glossary URL_RELPREFIX?= ../../../.. DOC_PREFIX?= ${.CURDIR}/../../.. # # rules generating lists of mirror site from XML database. # XMLDOCS= lastmod:::mirrors.lastmod.inc \ mirrors-ftp-index:::mirrors.xml.ftp.index.inc \ mirrors-ftp:::mirrors.xml.ftp.inc \ eresources-index:::eresources.xml.www.index.inc \ eresources:::eresources.xml.www.inc DEPENDSET.DEFAULT= transtable mirror XSLT.DEFAULT= ${XSL_MIRRORS} XML.DEFAULT= ${XML_MIRRORS} PARAMS.lastmod+= --param 'target' "'lastmod'" PARAMS.mirrors-ftp-index+= --param 'type' "'ftp'" \ --param 'proto' "'ftp'" \ --param 'target' "'index'" PARAMS.mirrors-ftp+= --param 'type' "'ftp'" \ --param 'proto' "'ftp'" \ --param 'target' "'handbook/mirrors/chapter.xml'" PARAMS.eresources-index+= --param 'type' "'www'" \ --param 'proto' "'http'" \ --param 'target' "'index'" PARAMS.eresources+= --param 'type' "'www'" \ --param 'proto' "'http'" \ --param 'target' "'handbook/eresources/chapter.xml'" SRCS+= mirrors.lastmod.inc \ mirrors.xml.ftp.inc \ mirrors.xml.ftp.index.inc \ eresources.xml.www.inc \ eresources.xml.www.index.inc .include "${DOC_PREFIX}/share/mk/doc.project.mk" Index: head/en_US.ISO8859-1/books/handbook/book.xml =================================================================== --- head/en_US.ISO8859-1/books/handbook/book.xml (revision 45601) +++ head/en_US.ISO8859-1/books/handbook/book.xml (revision 45602) @@ -1,307 +1,308 @@ %chapters; %txtfiles; ]> FreeBSD Handbook The FreeBSD Documentation Project $FreeBSD$ $FreeBSD$ 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 The FreeBSD Documentation Project &legalnotice; &tm-attrib.freebsd; &tm-attrib.3com; &tm-attrib.3ware; &tm-attrib.arm; &tm-attrib.adaptec; &tm-attrib.adobe; &tm-attrib.apple; &tm-attrib.creative; &tm-attrib.heidelberger; &tm-attrib.ibm; &tm-attrib.ieee; &tm-attrib.intel; &tm-attrib.intuit; &tm-attrib.linux; &tm-attrib.lsilogic; &tm-attrib.microsoft; &tm-attrib.opengroup; &tm-attrib.oracle; &tm-attrib.realnetworks; &tm-attrib.redhat; &tm-attrib.sun; &tm-attrib.themathworks; &tm-attrib.thomson; &tm-attrib.usrobotics; &tm-attrib.vmware; &tm-attrib.waterloomaple; &tm-attrib.wolframresearch; &tm-attrib.xfree86; &tm-attrib.xiph; &tm-attrib.general; Welcome to FreeBSD! This handbook covers the installation and day to day use of FreeBSD &rel3.current;-RELEASE, FreeBSD &rel2.current;-RELEASE, and FreeBSD &rel.current;-RELEASE. This manual is a work in progress and is the work of many individuals. As such, some sections may become dated and require updating. If you are interested in helping out with this project, send email to the &a.doc;. The latest version of this document is always available from the FreeBSD web site (previous versions of this handbook can be obtained from http://docs.FreeBSD.org/doc/). It may also be downloaded in a variety of formats and compression options from the FreeBSD FTP server or one of the numerous mirror sites. If you would prefer to have a hard copy of the handbook, you can purchase one at the FreeBSD Mall. You may also want to search the handbook. &chap.preface; Getting Started This part of the FreeBSD Handbook is for users and administrators who are new to FreeBSD. These chapters: Introduce you to FreeBSD. Guide you through the installation process. Teach you &unix; basics and fundamentals. Show you how to install the wealth of third party applications available for FreeBSD. Introduce you to X, the &unix; windowing system, and detail how to configure a desktop environment that makes you more productive. We have tried to keep the number of forward references in the text to a minimum so that you can read this section of the Handbook from front to back with the minimum page flipping required. &chap.introduction; &chap.bsdinstall; &chap.install; &chap.basics; &chap.ports; &chap.x11; Common Tasks Now that the basics have been covered, this part of the FreeBSD Handbook will discuss some frequently used features of FreeBSD. These chapters: Introduce you to popular and useful desktop applications: browsers, productivity tools, document viewers, etc. Introduce you to a number of multimedia tools available for FreeBSD. Explain the process of building a customized FreeBSD kernel, to enable extra functionality on your system. Describe the print system in detail, both for desktop and network-connected printer setups. Show you how to run Linux applications on your FreeBSD system. Some of these chapters recommend that you do some prior reading, and this is noted in the synopsis at the beginning of each chapter. &chap.desktop; &chap.multimedia; &chap.kernelconfig; &chap.printing; &chap.linuxemu; System Administration The remaining chapters of the FreeBSD Handbook cover all aspects of FreeBSD system administration. Each chapter starts by describing what you will learn as a result of reading the chapter, and also details what you are expected to know before tackling the material. These chapters are designed to be read when you need the information. You do not have to read them in any particular order, nor do you need to read all of them before you can begin using FreeBSD. &chap.config; &chap.boot; &chap.security; &chap.jails; &chap.mac; &chap.audit; &chap.disks; &chap.geom; + &chap.zfs; &chap.filesystems; &chap.virtualization; &chap.l10n; &chap.cutting-edge; &chap.dtrace; Network Communication FreeBSD is one of the most widely deployed operating systems for high performance network servers. The chapters in this part cover: Serial communication PPP and PPP over Ethernet Electronic Mail Running Network Servers Firewalls Other Advanced Networking Topics These chapters are designed to be read when you need the information. You do not have to read them in any particular order, nor do you need to read all of them before you can begin using FreeBSD in a network environment. &chap.serialcomms; &chap.ppp-and-slip; &chap.mail; &chap.network-servers; &chap.firewalls; &chap.advanced-networking; Appendices &chap.mirrors; &chap.bibliography; &chap.eresources; &chap.pgpkeys; &chap.freebsd-glossary; &chap.index; &chap.colophon; Index: head/en_US.ISO8859-1/books/handbook/bsdinstall/chapter.xml =================================================================== --- head/en_US.ISO8859-1/books/handbook/bsdinstall/chapter.xml (revision 45601) +++ head/en_US.ISO8859-1/books/handbook/bsdinstall/chapter.xml (revision 45602) @@ -1,2744 +1,2744 @@ Installing &os; 9.<replaceable>X</replaceable> and Later Jim Mock Restructured, reorganized, and parts rewritten by Gavin Atkinson Updated for bsdinstall by Warren Block Allan Jude Updated for root-on-ZFS by Synopsis installation Beginning with &os; 9.0-RELEASE, &os; provides an easy to use, text-based installation program named bsdinstall. This chapter describes how to install &os; using bsdinstall. The use of sysinstall, which is the installation program used by &os; 8.x, is covered in . In general, the installation instructions in this chapter are written for the &i386; and AMD64 architectures. Where applicable, instructions specific to other platforms will be listed. There may be minor differences between the installer and what is shown here, so use this chapter as a general guide rather than as a set of literal instructions. Users who prefer to install &os; using a graphical installer may be interested in pc-sysinstall, the installer used by the PC-BSD Project. It can be used to install either a graphical desktop (PC-BSD) or a command line version of &os;. Refer to the PC-BSD Users Handbook for details (http://wiki.pcbsd.org/index.php/PC-BSD%C2%AE_Users_Handbook/10.1). After reading this chapter, you will know: The minimum hardware requirements and &os; supported architectures. How to create the &os; installation media. How to start bsdinstall. The questions bsdinstall will ask, what they mean, and how to answer them. How to troubleshoot a failed installation. How to access a live version of &os; before committing to an installation. Before reading this chapter, you should: Read the supported hardware list that shipped with the version of &os; to be installed and verify that the system's hardware is supported. Minimum Hardware Requirements The hardware requirements to install &os; vary by the &os; version and the hardware architecture. Hardware architectures and devices supported by a &os; release are listed in the Hardware Notes file. Usually named HARDWARE.TXT, the file is located in the root directory of the release media. Copies of the supported hardware list are also available on the Release Information page of the &os; web site (http://www.FreeBSD.org/releases/index.html). A &os; installation will require at least 64 MB of RAM and 1.5 GB of free hard drive space for the most minimal installation. However, that is a very minimal install, leaving almost no free space. A more realistic minimum is 4 GB without a graphical environment, and 8 GB or more if a graphical user interface will be used. Third-party application software requires more space. It is recommended to increase RAM and hard drive space to meet the needs of the applications that will be used and the amount of data that will be stored. The processor requirements for each architecture can be summarized as follows: &arch.amd64; There are two classes of processors capable of running &arch.amd64;. The first are AMD64 processors, including the &amd.athlon;64 and &amd.opteron; processors. The second class of processors includes those using the &intel; EM64T architecture. Examples of these processors include all multi-core &intel; &xeon; processors except Sossaman, the single-core &intel; &xeon; processors Nocona, Irwindale, Potomac, and Cranford, the &intel; &core; 2 (not Core Duo) and later processors, all &intel; &pentium; D processors, the &intel; &pentium; 4s and Celeron Ds using the Cedar Mill core, and some &intel; &pentium; 4s and Celeron Ds using the Prescott core. Both Uniprocessor (UP) and Symmetric Multi-processor (SMP) configurations are supported. &arch.i386; Almost all i386-compatible processors with a floating point unit are supported. All &intel; processors 486 or higher are supported. &os; will take advantage of Physical Address Extensions (PAE) support on CPUs that support this feature. A kernel with the PAE feature enabled will detect memory above 4 GB and allow it to be used by the system. This feature places constraints on the device drivers and other features of &os; which may be used; refer to &man.pae.4; for details. ia64 Currently supported processors are the &itanium; and the &itanium; 2. Supported chipsets include the HP zx1, &intel; 460GX, and &intel; E8870. Both Uniprocessor (UP) and Symmetric Multi-processor (SMP) configurations are supported. pc98 NEC PC-9801/9821 series with almost all i386-compatible processors, including 80486, &pentium;, &pentium; Pro, and &pentium; II, are all supported. All i386-compatible processors by AMD, Cyrix, IBM, and IDT are also supported. EPSON PC-386/486/586 series, which are compatible with NEC PC-9801 series, are supported. The NEC FC-9801/9821 and NEC SV-98 series should be supported. High-resolution mode is not supported. NEC PC-98XA/XL/RL/XL^2, and NEC PC-H98 series are supported in normal (PC-9801 compatible) mode only. The SMP-related features of &os; are not supported. The New Extend Standard Architecture (NESA) bus used in the PC-H98, SV-H98, and FC-H98 series, is not supported. &arch.powerpc; All New World ROM &apple; &macintosh; systems with built-in USB are supported. SMP is supported on machines with multiple CPUs. A 32-bit kernel can only use the first 2 GB of RAM. &arch.sparc64; Systems supported by &os;/&arch.sparc64; are listed at the FreeBSD/sparc64 Project (http://www.freebsd.org/platforms/sparc.html). SMP is supported on all systems with more than 1 processor. A dedicated disk is required as it is not possible to share a disk with another operating system at this time. Pre-Installation Tasks Once it has been determined that the system meets the minimum hardware requirements for installing &os;, the installation file should be downloaded and the installation media prepared. Before doing this, check that the system is ready for an installation by verifying the items in this checklist: Back Up Important Data Before installing any operating system, always backup all important data first. Do not store the backup on the system being installed. Instead, save the data to a removable disk such as a USB drive, another system on the network, or an online backup service. Test the backup before starting the installation to make sure it contains all of the needed files. Once the installer formats the system's disk, all data stored on that disk will be lost. Decide Where to Install &os; If &os; will be the only operating system installed, this step can be skipped. But if &os; will share the disk with another operating system, decide which disk or partition will be used for &os;. In the &arch.i386; and &arch.amd64; architectures, disks can be divided into multiple partitions using one of two partitioning schemes. A traditional Master Boot Record (MBR) holds a partition table defining up to four primary partitions. For historical reasons, &os; calls these primary partition slices. One of these primary partitions can be made into an extended partition containing multiple logical partitions. The GUID Partition Table (GPT) is a newer and simpler method of partitioning a disk. Common GPT implementations allow up to 128 partitions per disk, eliminating the need for logical partitions. Some older operating systems, like &windows; XP, are not compatible with the GPT partition scheme. If &os; will be sharing a disk with such an operating system, MBR partitioning is required. The &os; boot loader requires either a primary or GPT partition. If all of the primary or GPT partitions are already in use, one must be freed for &os;. To create a partition without deleting existing data, use a partition resizing tool to shrink an existing partition and create a new partition using the freed space. A variety of free and commercial partition resizing tools are listed at http://en.wikipedia.org/wiki/List_of_disk_partitioning_software. GParted Live (http://gparted.sourceforge.net/livecd.php) is a free live CD which includes the GParted partition editor. GParted is also included with many other Linux live CD distributions. When used properly, disk shrinking utilities can safely create space for creating a new partition. Since the possibility of selecting the wrong partition exists, always backup any important data and verify the integrity of the backup before modifying disk partitions. Disk partitions containing different operating systems make it possible to install multiple operating systems on one computer. An alternative is to use virtualization () which allows multiple operating systems to run at the same time without modifying any disk partitions. Collect Network Information Some &os; installation methods require a network connection in order to download the installation files. After any installation, the installer will offer to setup the system's network interfaces. If the network has a DHCP server, it can be used to provide automatic network configuration. If DHCP is not available, the following network information for the system must be obtained from the local network administrator or Internet service provider: Required Network Information IP address Subnet mask IP address of default gateway Domain name of the network IP addresses of the network's DNS servers Check for &os; Errata Although the &os; Project strives to ensure that each release of &os; is as stable as possible, bugs occasionally creep into the process. On very rare occasions those bugs affect the installation process. As these problems are discovered and fixed, they are noted in the &os; Errata (http://www.freebsd.org/releases/&rel.current;R/errata.html) on the &os; web site. Check the errata before installing to make sure that there are no problems that might affect the installation. Information and errata for all the releases can be found on the release information section of the &os; web site (http://www.freebsd.org/releases/index.html). Prepare the Installation Media The &os; installer is not an application that can be run from within another operating system. Instead, download a &os; installation file, burn it to the media associated with its file type and size (CD, DVD, or USB), and boot the system to install from the inserted media. &os; installation files are available at www.freebsd.org/where.html#download. Each installation file's name includes the release version of &os;, the architecture, and the type of file. For example, to install &os; 10.0 on an &arch.amd64; system from a DVD, download FreeBSD-10.0-RELEASE-amd64-dvd1.iso, burn this file to a DVD, and boot the system with the DVD inserted. Several file types are available, though not all file types are available for all architectures. The possible file types are: -bootonly.iso: This is the smallest installation file as it only contains the installer. A working Internet connection is required during installation as the installer will download the files it needs to complete the &os; installation. This file should be burned to a CD using a CD burning application. -disc1.iso: This file contains all of the files needed to install &os;, its source, and the Ports Collection. It should be burned to a CD using a CD burning application. -dvd1.iso: This file contains all of the files needed to install &os;, its source, and the Ports Collection. It also contains a set of popular binary packages for installing a window manager and some applications so that a complete system can be installed from media without requiring a connection to the Internet. This file should be burned to a DVD using a DVD burning application. -memstick.img: This file contains all of the files needed to install &os;, its source, and the Ports Collection. It should be burned to a USB stick using the instructions below. Also download CHECKSUM.SHA256 from the same directory as the image file and use it to check the image file's integrity by calculating a checksum. &os; provides &man.sha256.1; for this, while other operating systems have similar programs. Compare the calculated checksum with the one shown in CHECKSUM.SHA256. The checksums must match exactly. If the checksums do not match, the file is corrupt and should be downloaded again. Writing an Image File to <acronym>USB</acronym> The *.img file is an image of the complete contents of a memory stick. It cannot be copied to the target device as a file. Several applications are available for writing the *.img to a USB stick. This section describes two of these utilities. Before proceeding, back up any important data on the USB stick. This procedure will erase the existing data on the stick. Using <command>dd</command> to Write the Image This example uses /dev/da0 as the target device where the image will be written. Be very careful that the correct device is used as this command will destroy the existing data on the specified target device. The &man.dd.1; command-line utility is available on BSD, &linux;, and &macos; systems. To burn the image using dd, insert the USB stick and determine its device name. Then, specify the name of the downloaded installation file and the device name for the USB stick. This example burns the &arch.amd64; installation image to the first USB device on an existing &os; system. &prompt.root; dd if=FreeBSD-10.0-RELEASE-amd64-memstick.img of=/dev/da0 bs=64k If this command fails, verify that the USB stick is not mounted and that the device name is for the disk, not a partition. Some operating systems might require this command to be run with &man.sudo.8;. Systems like &linux; might buffer writes. To force all writes to complete, use &man.sync.8;. Using &windows; to Write the Image Be sure to give the correct drive letter as the existing data on the specified drive will be overwritten and destroyed. Obtaining <application>Image Writer for &windows;</application> Image Writer for &windows; is a free application that can correctly write an image file to a memory stick. Download it from https://launchpad.net/win32-image-writer/ and extract it into a folder. Writing the Image with Image Writer Double-click the Win32DiskImager icon to start the program. Verify that the drive letter shown under Device is the drive with the memory stick. Click the folder icon and select the image to be written to the memory stick. Click [ Save ] to accept the image file name. Verify that everything is correct, and that no folders on the memory stick are open in other windows. When everything is ready, click [ Write ] to write the image file to the memory stick. You are now ready to start installing &os;. Starting the Installation By default, the installation will not make any changes to the disk(s) before the following message: Your changes will now be written to disk. If you have chosen to overwrite existing data, it will be PERMANENTLY ERASED. Are you sure you want to commit your changes? The install can be exited at any time prior to this warning. If there is a concern that something is incorrectly configured, just turn the computer off before this point and no changes will be made to the system's disks. This section describes how to boot the system from the installation media which was prepared using the instructions in . When using a bootable USB stick, plug in the USB stick before turning on the computer. When booting from CD or DVD, turn on the computer and insert the media at the first opportunity. How to configure the system to boot from the inserted media depends upon the architecture. Booting on &i386; and &arch.amd64; These architectures provide a BIOS menu for selecting the boot device. Depending upon the installation media being used, select the CD/DVD or USB device as the first boot device. Most systems also provide a key for selecting the boot device during startup without having to enter the BIOS. Typically, the key is either F10, F11, F12, or Escape. If the computer loads the existing operating system instead of the &os; installer, then either: The installation media was not inserted early enough in the boot process. Leave the media inserted and try restarting the computer. The BIOS changes were incorrect or not saved. Double-check that the right boot device is selected as the first boot device. This system is too old to support booting from the chosen media. In this case, the Plop Boot Manager (http://www.plop.at/en/bootmanager.html) can be used to boot the system from the selected media. Booting on &powerpc; On most machines, holding C on the keyboard during boot will boot from the CD. Otherwise, hold Command Option O F , or Windows Alt O F on non-&apple; keyboards. At the 0 > prompt, enter boot cd:,\ppc\loader cd:0 Booting on &sparc64; Most &sparc64; systems are set up to boot automatically from disk. To install &os; from a CD requires a break into the PROM. To do this, reboot the system and wait until the boot message appears. The message depends on the model, but should look something like this: Sun Blade 100 (UltraSPARC-IIe), Keyboard Present Copyright 1998-2001 Sun Microsystems, Inc. All rights reserved. OpenBoot 4.2, 128 MB memory installed, Serial #51090132. Ethernet address 0:3:ba:b:92:d4, Host ID: 830b92d4. If the system proceeds to boot from disk at this point, press L1A or StopA on the keyboard, or send a BREAK over the serial console. When using tip or cu, ~# will issue a BREAK. The PROM prompt will be ok on systems with one CPU and ok {0} on SMP systems, where the digit indicates the number of the active CPU. At this point, place the CD into the drive and type boot cdrom from the PROM prompt. &os; Boot Menu Once the system boots from the installation media, a menu similar to the following will be displayed:
&os; Boot Loader Menu
By default, the menu will wait ten seconds for user input before booting into the &os; installer or, if &os; is already installed, before booting into &os;. To pause the boot timer in order to review the selections, press Space. To select an option, press its highlighted number, character, or key. The following options are available. Boot Multi User: This will continue the &os; boot process. If the boot timer has been paused, press 1, upper- or lower-case B, or Enter. Boot Single User: This mode can be used to fix an existing &os; installation as described in . Press 2 or the upper- or lower-case S to enter this mode. Escape to loader prompt: This will boot the system into a repair prompt that contains a limited number of low-level commands. This prompt is described in . Press 3 or Esc to boot into this prompt. Reboot: Reboots the system. Configure Boot Options: Opens the menu shown in, and described under, .
&os; Boot Options Menu
The boot options menu is divided into two sections. The first section can be used to either return to the main boot menu or to reset any toggled options back to their defaults. The next section is used to toggle the available options to On or Off by pressing the option's highlighted number or character. The system will always boot using the settings for these options until they are modified. Several options can be toggled using this menu: ACPI Support: If the system hangs during boot, try toggling this option to Off. Safe Mode: If the system still hangs during boot even with ACPI Support set to Off, try setting this option to On. Single User: Toggle this option to On to fix an existing &os; installation as described in . Once the problem is fixed, set it back to Off. Verbose: Toggle this option to On to see more detailed messages during the boot process. This can be useful when troubleshooting a piece of hardware. After making the needed selections, press 1 or Backspace to return to the main boot menu, then press Enter to continue booting into &os;. A series of boot messages will appear as &os; carries out its hardware device probes and loads the installation program. Once the boot is complete, the welcome menu shown in will be displayed.
Welcome Menu
Press Enter to select the default of [ Install ] to enter the installer. The rest of this chapter describes how to use this installer. Otherwise, use the right or left arrows or the colorized letter to select the desired menu item. The [ Shell ] can be used to access a &os; shell in order to use command line utilities to prepare the disks before installation. The [ Live CD ] option can be used to try out &os; before installing it. The live version is described in . To review the boot messages, including the hardware device probe, press the upper- or lower-case S and then Enter to access a shell. At the shell prompt, type more /var/run/dmesg.boot and use the space bar to scroll through the messages. When finished, type exit to return to the welcome menu. Using <application>bsdinstall</application> This section shows the order of the bsdinstall menus and the type of information that will be asked before the system is installed. Use the arrow keys to highlight a menu option, then Space to select or deselect that menu item. When finished, press Enter to save the selection and move onto the next screen. Selecting the Keymap Menu Depending on the system console being used, bsdinstall may initially display the menu shown in .
Keymap Selection
To configure the keyboard layout, press Enter with [ YES ] selected, which will display the menu shown in . To instead use the default layout, use the arrow key to select [ NO ] and press Enter to skip this menu screen.
Selecting Keyboard Menu
When configuring the keyboard layout, use the up and down arrows to select the keymap that most closely represents the mapping of the keyboard attached to the system. Press Enter to save the selection. Pressing Esc will exit this menu and use the default keymap. If the choice of keymap is not clear, United States of America ISO-8859-1 is also a safe option. In &os; 10.0-RELEASE and later, this menu has been enhanced. The full selection of keymaps is shown, with the default preselected. In addition, when selecting a different keymap, a dialog is displayed that allows the user to try the keymap and ensure it is correct before proceeding.
Enhanced Keymap Menu
Setting the Hostname The next bsdinstall menu is used to set the hostname for the newly installed system.
Setting the Hostname
Type in a hostname that is unique for the network. It should be a fully-qualified hostname, such as machine3.example.com. Selecting Components to Install Next, bsdinstall will prompt to select optional components to install.
Selecting Components to Install
Deciding which components to install will depend largely on the intended use of the system and the amount of disk space available. The &os; kernel and userland, collectively known as the base system, are always installed. Depending on the architecture, some of these components may not appear: doc - Additional documentation, mostly of historical interest, to install into /usr/share/doc. The documentation provided by the FreeBSD Documentation Project may be installed later using the instructions in . games - Several traditional BSD games, including fortune, rot13, and others. lib32 - Compatibility libraries for running 32-bit applications on a 64-bit version of &os;. ports - The &os; Ports Collection is a collection of files which automates the downloading, compiling and installation of third-party software packages. discusses how to use the Ports Collection. The installation program does not check for adequate disk space. Select this option only if sufficient hard disk space is available. The &os; Ports Collection takes up about &ports.size; of disk space. src - The complete &os; source code for both the kernel and the userland. Although not required for the majority of applications, it may be required to build device drivers, kernel modules, or some applications from the Ports Collection. It is also used for developing &os; itself. The full source tree requires 1 GB of disk space and recompiling the entire &os; system requires an additional 5 GB of space. Installing from the Network The menu shown in only appears when installing from a -bootonly.iso CD as this installation media does not hold copies of the installation files. Since the installation files must be retrieved over a network connection, this menu indicates that the network interface must be first configured.
Installing from the Network
To configure the network connection, press Enter and follow the instructions in . Once the interface is configured, select a mirror site that is located in the same region of the world as the computer on which &os; is being installed. Files can be retrieved more quickly when the mirror is close to the target computer, reducing installation time.
Choosing a Mirror
Installation will then continue as if the installation files were located on the local installation media. Allocating Disk Space The next menu is used to determine the method for allocating disk space. The options available in the menu depend upon the version of &os; being installed.
Partitioning Choices on &os; 9.x
Partitioning Choices on &os; 10.x and Higher
Guided partitioning automatically sets up the disk partitions, Manual partitioning allows advanced users to create customized partitions from menu options, and Shell opens a shell prompt where advanced users can create customized partitions using command-line utilities like &man.gpart.8;, &man.fdisk.8;, and &man.bsdlabel.8;. ZFS partitioning, only available in &os; 10 and later, creates an optionally encrypted root-on-ZFS system with support for boot environments. This section describes what to consider when laying out the disk partitions. It then demonstrates how to use the different partitioning methods. Designing the Partition Layout partition layout /etc /var /usr When laying out file systems, remember that hard drives transfer data faster from the outer tracks to the inner. Thus, smaller and heavier-accessed file systems should be closer to the outside of the drive, while larger partitions like /usr should be placed toward the inner parts of the disk. It is a good idea to create partitions in an order similar to: /, swap, /var, and /usr. The size of the /var partition reflects the intended machine's usage. This partition is used to hold mailboxes, log files, and printer spools. Mailboxes and log files can grow to unexpected sizes depending on the number of users and how long log files are kept. On average, most users rarely need more than about a gigabyte of free disk space in /var. Sometimes, a lot of disk space is required in /var/tmp. When new software is installed, the packaging tools extract a temporary copy of the packages under /var/tmp. Large software packages, like Firefox, OpenOffice or LibreOffice may be tricky to install if there is not enough disk space under /var/tmp. The /usr partition holds many of the files which support the system, including the &os; Ports Collection and system source code. At least 2 gigabytes is recommended for this partition. When selecting partition sizes, keep the space requirements in mind. Running out of space in one partition while barely using another can be a hassle. swap sizing swap partition As a rule of thumb, the swap partition should be about double the size of physical memory (RAM). Systems with minimal RAM may perform better with more swap. Configuring too little swap can lead to inefficiencies in the VM page scanning code and might create issues later if more memory is added. On larger systems with multiple SCSI disks or multiple IDE disks operating on different controllers, it is recommended that swap be configured on each drive, up to four drives. The swap partitions should be approximately the same size. The kernel can handle arbitrary sizes but internal data structures scale to 4 times the largest swap partition. Keeping the swap partitions near the same size will allow the kernel to optimally stripe swap space across disks. Large swap sizes are fine, even if swap is not used much. It might be easier to recover from a runaway program before being forced to reboot. By properly partitioning a system, fragmentation introduced in the smaller write heavy partitions will not bleed over into the mostly read partitions. Keeping the write loaded partitions closer to the disk's edge will increase I/O performance in the partitions where it occurs the most. While I/O performance in the larger partitions may be needed, shifting them more toward the edge of the disk will not lead to a significant performance improvement over moving /var to the edge. Guided Partitioning When this method is selected, a menu will display the available disk(s). If multiple disks are connected, choose the one where &os; is to be installed.
Selecting from Multiple Disks
Once the disk is selected, the next menu prompts to install to either the entire disk or to create a partition using free space. If [ Entire Disk ] is chosen, a general partition layout filling the whole disk is automatically created. Selecting [ Partition ] creates a partition layout from the unused space on the disk.
Selecting Entire Disk or Partition
After the partition layout has been created, review it to ensure it meets the needs of the installation. Selecting [ Revert ] will reset the partitions to their original values and pressing [ Auto ] will recreate the automatic &os; partitions. Partitions can also be manually created, modified, or deleted. When the partitioning is correct, select [ Finish ] to continue with the installation.
Review Created Partitions
Manual Partitioning Selecting this method opens the partition editor:
Manually Create Partitions
Highlight the installation drive (ada0 in this example) and select [ Create ] to display a menu of available partition schemes:
Manually Create Partitions
GPT is usually the most appropriate choice for &arch.amd64; computers. Older computers that are not compatible with GPT should use MBR. The other partition schemes are generally used for uncommon or older computers. Partitioning Schemes Abbreviation Description APM Apple Partition Map, used by &powerpc;. BSD BSD label without an MBR, sometimes called dangerously dedicated mode as non-BSD disk utilities may not recognize it. GPT GUID Partition Table (http://en.wikipedia.org/wiki/GUID_Partition_Table). MBR Master Boot Record (http://en.wikipedia.org/wiki/Master_boot_record). PC98 MBR variant used by NEC PC-98 computers (http://en.wikipedia.org/wiki/Pc9801). VTOC8 Volume Table Of Contents used by Sun SPARC64 and UltraSPARC computers.
After the partitioning scheme has been selected and created, select [ Create ] again to create the partitions.
Manually Create Partitions
A standard &os; GPT installation uses at least three partitions: freebsd-boot - Holds the &os; boot code. freebsd-ufs - A &os; UFS file system. freebsd-swap - &os; swap space. Another partition type worth noting is freebsd-zfs, used for partitions that will contain a &os; ZFS file system (). Refer to &man.gpart.8; for + linkend="zfs"/>). Refer to &man.gpart.8; for descriptions of the available GPT partition types. Multiple file system partitions can be created and some people prefer a traditional layout with separate partitions for the /, /var, /tmp, and /usr file systems. See for an example. The Size may be entered with common abbreviations: K for kilobytes, M for megabytes, or G for gigabytes. Proper sector alignment provides the best performance, and making partition sizes even multiples of 4K-bytes helps to ensure alignment on drives with either 512-byte or 4K-byte sectors. Generally, using partition sizes that are even multiples of 1M or 1G is the easiest way to make sure every partition starts at an even multiple of 4K. There is one exception: the freebsd-boot partition should be no larger than 512K due to current boot code limitations. A Mountpoint is needed if the partition will contain a file system. If only a single UFS partition will be created, the mountpoint should be /. The Label is a name by which the partition will be known. Drive names or numbers can change if the drive is connected to a different controller or port, but the partition label does not change. Referring to labels instead of drive names and partition numbers in files like /etc/fstab makes the system more tolerant to hardware changes. GPT labels appear in /dev/gpt/ when a disk is attached. Other partitioning schemes have different label capabilities and their labels appear in different directories in /dev/. Use a unique label on every partition to avoid conflicts from identical labels. A few letters from the computer's name, use, or location can be added to the label. For instance, use labroot or rootfslab for the UFS root partition on the computer named lab. Creating Traditional Split File System Partitions For a traditional partition layout where the /, /var, /tmp, and /usr directories are separate file systems on their own partitions, create a GPT partitioning scheme, then create the partitions as shown. Partition sizes shown are typical for a 20G target disk. If more space is available on the target disk, larger swap or /var partitions may be useful. Labels shown here are prefixed with ex for example, but readers should use other unique label values as described above. By default, &os;'s gptboot expects the first UFS partition to be the / partition. Partition Type Size Mountpoint Label freebsd-boot 512K freebsd-ufs 2G / exrootfs freebsd-swap 4G exswap freebsd-ufs 2G /var exvarfs freebsd-ufs 1G /tmp extmpfs freebsd-ufs accept the default (remainder of the disk) /usr exusrfs After the custom partitions have been created, select [ Finish ] to continue with the installation. Root-on-ZFS Automatic Partitioning Support for automatic creation of root-on-ZFS installations was added in &os; 10.0-RELEASE. This partitioning mode only works with whole disks and will erase the contents of the entire disk. The installer will automatically create partitions aligned to 4k boundaries and force ZFS to use 4k sectors. This is safe even with 512 byte sector disks, and has the added benefit of ensuring that pools created on 512 byte disks will be able to have 4k sector disks added in the future, either as additional storage space or as replacements for failed disks. The installer can also optionally employ GELI disk encryption as described in . If encryption is enabled, a 2 GB unencrypted boot pool containing the /boot directory is created. It holds the kernel and other files necessary to boot the system. A swap partition of a user selectable size is also created, and all remaining space is used for the ZFS pool. The main ZFS configuration menu offers a number of options to control the creation of the pool.
<acronym>ZFS</acronym> Partitioning Menu
Select T to configure the Pool Type and the disk(s) that will constitute the pool. The automatic ZFS installer currently only supports the creation of a single top level vdev, except in stripe mode. To create more complex pools, use the instructions in to create the pool. The installer supports the creation of various pool types, including stripe (not recommended, no redundancy), mirror (best performance, least usable space), and RAID-Z 1, 2, and 3 (with the capability to withstand the concurrent failure of 1, 2, and 3 disks, respectively). while selecting the pool type, a tooltip is displayed across the bottom of the screen with advice about the number of required disks, and in the case of RAID-Z, the optimal number of disks for each configuration.
<acronym>ZFS</acronym> Pool Type
Once a Pool Type has been selected, a list of available disks is displayed, and the user is prompted to select one or more disks to make up the pool. The configuration is then validated, to ensure enough disks are selected. If not, select <Change Selection> to return to the list of disks, or <Cancel> to change the pool type.
Disk Selection
Invalid Selection
If one or more disks are missing from the list, or if disks were attached after the installer was started, select - Rescan Devices to repopulate the list of available disks. To ensure that the correct disks are selected, so as not to accidently destroy the wrong disks, the - Disk Info menu can be used to inspect each disk, including its partition table and various other information such as the device model number and serial number, if available.
Analysing a Disk
The main ZFS configuration menu also allows the user to enter a pool name, disable forcing 4k sectors, enable or disable encryption, switch between GPT (recommended) and MBR partition table types, and select the amount of swap space. Once all options have been set to the desired values, select the >>> Install option at the top of the menu. If GELI disk encryption was enabled, the installer will prompt twice for the passphrase to be used to encrypt the disks.
Disk Encryption Password
The installer then offers a last chance to cancel before the contents of the selected drives are destroyed to create the ZFS pool.
Last Chance
The installation then proceeds normally. Shell Mode Partitioning When creating advanced installations, the bsdinstall paritioning menus may not provide the level of flexibility required. Advanced users can select the Shell option from the partitioning menu in order to manually partition the drives, create the file system(s), populate /tmp/bsdinstall_etc/fstab, and mount the file systems under /mnt. Once this is done, type exit to return to bsdinstall and continue the installation. Committing to the Installation Once the disks are configured, the next menu provides the last chance to make changes before the selected hard drive(s) are formatted. If changes need to be made, select [ Back ] to return to the main partitioning menu. [ Revert & Exit ] will exit the installer without making any changes to the hard drive.
Final Confirmation
To instead start the actual installation, select [ Commit ] and press Enter. Installation time will vary depending on the distributions chosen, installation media, and speed of the computer. A series of messages will indicate the progress. First, the installer formats the selected disk(s) and initializes the partitions. Next, in the case of a bootonly media, it downloads the selected components:
Fetching Distribution Files
Next, the integrity of the distribution files is verified to ensure they have not been corrupted during download or misread from the installation media:
Verifying Distribution Files
Finally, the verified distribution files are extracted to the disk:
Extracting Distribution Files
Once all requested distribution files have been extracted, bsdinstall displays the first post-installation configuration screen. The available post-configuration options are described in the next section. Post-Installation Once &os; is installed, bsdinstall will prompt to configure several options before booting into the newly installed system. This section describes these configuration options. Once the system has booted, bsdconfig provides a menu-driven method for configuring the system using these and additional options. Setting the <systemitem class="username">root</systemitem> Password First, the root password must be set. While entering the password, the characters being typed are not displayed on the screen. After the password has been entered, it must be entered again. This helps prevent typing errors.
Setting the <systemitem class="username">root</systemitem> Password
Configuring Network Interfaces Next, a list of the network interfaces found on the computer is shown. Select the interface to configure. The network configuration menus will be skipped if the network was previously configured as part of a bootonly installation.
Choose a Network Interface
If an Ethernet interface is selected, the installer will skip ahead to the menu shown in . If a wireless network interface is chosen, the system will instead scan for wireless access points:
Scanning for Wireless Access Points
Wireless networks are identified by a Service Set Identifier (SSID), a short, unique name given to each network. SSIDs found during the scan are listed, followed by a description of the encryption types available for that network. If the desired SSID does not appear in the list, select [ Rescan ] to scan again. If the desired network still does not appear, check for problems with antenna connections or try moving the computer closer to the access point. Rescan after each change is made.
Choosing a Wireless Network
Next, enter the encryption information for connecting to the selected wireless network. WPA2 encryption is strongly recommended as older encryption types, like WEP, offer little security. If the network uses WPA2, input the password, also known as the Pre-Shared Key (PSK). For security reasons, the characters typed into the input box are displayed as asterisks.
WPA2 Setup
Next, choose whether or not an IPv4 address should be configured on the Ethernet or wireless interface:
Choose <acronym>IPv4</acronym> Networking
There are two methods of IPv4 configuration. DHCP will automatically configure the network interface correctly and should be used if the network provides a DHCP server. Otherwise, the addressing information needs to be input manually as a static configuration. Do not enter random network information as it will not work. If a DHCP server is not available, obtain the information listed in from the network administrator or Internet service provider. If a DHCP server is available, select [ Yes ] in the next menu to automatically configure the network interface. The installer will appear to pause for a minute or so as it finds the DHCP server and obtains the addressing information for the system.
Choose <acronym>IPv4</acronym> <acronym>DHCP</acronym> Configuration
If a DHCP server is not available, select [ No ] and input the following addressing information in this menu:
<acronym>IPv4</acronym> Static Configuration
IP Address - The IPv4 address assigned to this computer. The address must be unique and not already in use by another piece of equipment on the local network. Subnet Mask - The subnet mask for the network. Default Router - The IP address of the network's default gateway. The next screen will ask if the interface should be configured for IPv6. If IPv6 is available and desired, choose [ Yes ] to select it.
Choose IPv6 Networking
IPv6 also has two methods of configuration. StateLess Address AutoConfiguration (SLAAC) will automatically request the correct configuration information from a local router. Refer to http://tools.ietf.org/html/rfc4862 for more information. Static configuration requires manual entry of network information. If an IPv6 router is available, select [ Yes ] in the next menu to automatically configure the network interface. The installer will appear to pause for a minute or so as it finds the router and obtains the addressing information for the system.
Choose IPv6 SLAAC Configuration
If an IPv6 router is not available, select [ No ] and input the following addressing information in this menu:
IPv6 Static Configuration
IPv6 Address - The IPv6 address assigned to this computer. The address must be unique and not already in use by another piece of equipment on the local network. Default Router - The IPv6 address of the network's default gateway. The last network configuration menu is used to configure the Domain Name System (DNS) resolver, which converts hostnames to and from network addresses. If DHCP or SLAAC was used to autoconfigure the network interface, the Resolver Configuration values may already be filled in. Otherwise, enter the local network's domain name in the Search field. DNS #1 and DNS #2 are the IPv4 and/or IPv6 addresses of the DNS servers. At least one DNS server is required.
DNS Configuration
Setting the Time Zone The next menu asks if the system clock uses UTC or local time. When in doubt, select [ No ] to choose the more commonly-used local time.
Select Local or UTC Clock
The next series of menus are used to determine the correct local time by selecting the geographic region, country, and time zone. Setting the time zone allows the system to automatically correct for regional time changes, such as daylight savings time, and perform other time zone related functions properly. The example shown here is for a machine located in the Eastern time zone of the United States. The selections will vary according to the geographical location.
Select a Region
The appropriate region is selected using the arrow keys and then pressing Enter.
Select a Country
Select the appropriate country using the arrow keys and press Enter.
Select a Time Zone
The appropriate time zone is selected using the arrow keys and pressing Enter.
Confirm Time Zone
Confirm the abbreviation for the time zone is correct. If it is, press Enter to continue with the post-installation configuration. Enabling Services The next menu is used to configure which system services will be started whenever the system boots. All of these services are optional. Only start the services that are needed for the system to function.
Selecting Additional Services to Enable
Here is a summary of the services which can be enabled in this menu: sshd - The Secure Shell (SSH) daemon is used to remotely access a system over an encrypted connection. Only enable this service if the system should be available for remote logins. moused - Enable this service if the mouse will be used from the command-line system console. ntpd - The Network Time Protocol (NTP) daemon for automatic clock synchronization. Enable this service if there is a &windows;, Kerberos, or LDAP server on the network. powerd - System power control utility for power control and energy saving. Enabling Crash Dumps The next menu is used to configure whether or not crash dumps should be enabled. Enabling crash dumps can be useful in debugging issues with the system, so users are encouraged to enable crash dumps.
Enabling Crash Dumps
Add Users The next menu prompts to create at least one user account. It is recommended to login to the system using a user account rather than as root. When logged in as root, there are essentially no limits or protection on what can be done. Logging in as a normal user is safer and more secure. Select [ Yes ] to add new users.
Add User Accounts
Follow the prompts and input the requested information for the user account. The example shown in creates the asample user account.
Enter User Information
Here is a summary of the information to input: Username - The name the user will enter to log in. A common convention is to use the first letter of the first name combined with the last name, as long as each username is unique for the system. The username is case sensitive and should not contain any spaces. Full name - The user's full name. This can contain spaces and is used as a description for the user account. Uid - User ID. Typically, this is left blank so the system will assign a value. Login group - The user's group. Typically this is left blank to accept the default. Invite user into other groups? - Additional groups to which the user will be added as a member. If the user needs administrative access, type wheel here. Login class - Typically left blank for the default. Shell - Type in one of the listed values to set the interactive shell for the user. Refer to for more information about shells. Home directory - The user's home directory. The default is usually correct. Home directory permissions - Permissions on the user's home directory. The default is usually correct. Use password-based authentication? - Typically yes so that the user is prompted to input their password at login. Use an empty password? - Typically no as it is insecure to have a blank password. Use a random password? - Typically no so that the user can set their own password in the next prompt. Enter password - The password for this user. Characters typed will not show on the screen. Enter password again - The password must be typed again for verification. Lock out the account after creation? - Typically no so that the user can login. After entering everything, a summary is shown for review. If a mistake was made, enter no and try again. If everything is correct, enter yes to create the new user.
Exit User and Group Management
If there are more users to add, answer the Add another user? question with yes. Enter no to finish adding users and continue the installation. For more information on adding users and user management, see . Final Configuration After everything has been installed and configured, a final chance is provided to modify settings.
Final Configuration
Use this menu to make any changes or do any additional configuration before completing the installation. Add User - Described in . Root Password - Described in . Hostname - Described in . Network - Described in . Services - Described in . Time Zone - Described in . Handbook - Download and install the &os; Handbook. After any final configuration is complete, select Exit.
Manual Configuration
bsdinstall will prompt if there are any additional configuration that needs to be done before rebooting into the new system. Select [ Yes ] to exit to a shell within the new system or [ No ] to proceed to the last step of the installation.
Complete the Installation
If further configuration or special setup is needed, select [ Live CD ] to boot the install media into Live CD mode. If the installation is complete, select [ Reboot ] to reboot the computer and start the new &os; system. Do not forget to remove the &os; install media or the computer may boot from it again. As &os; boots, informational messages are displayed. After the system finishes booting, a login prompt is displayed. At the login: prompt, enter the username added during the installation. Avoid logging in as root. Refer to for instructions on how to become the superuser when administrative access is needed. The messages that appeared during boot can be reviewed by pressing Scroll-Lock to turn on the scroll-back buffer. The PgUp, PgDn, and arrow keys can be used to scroll back through the messages. When finished, press Scroll-Lock again to unlock the display and return to the console. To review these messages once the system has been up for some time, type less /var/run/dmesg.boot from a command prompt. Press q to return to the command line after viewing. If sshd was enabled in , the first boot may be a bit slower as the system will generate the RSA and DSA keys. Subsequent boots will be faster. The fingerprints of the keys will be displayed, as seen in this example: Generating public/private rsa1 key pair. Your identification has been saved in /etc/ssh/ssh_host_key. Your public key has been saved in /etc/ssh/ssh_host_key.pub. The key fingerprint is: 10:a0:f5:af:93:ae:a3:1a:b2:bb:3c:35:d9:5a:b3:f3 root@machine3.example.com The key's randomart image is: +--[RSA1 1024]----+ | o.. | | o . . | | . o | | o | | o S | | + + o | |o . + * | |o+ ..+ . | |==o..o+E | +-----------------+ Generating public/private dsa key pair. Your identification has been saved in /etc/ssh/ssh_host_dsa_key. Your public key has been saved in /etc/ssh/ssh_host_dsa_key.pub. The key fingerprint is: 7e:1c:ce:dc:8a:3a:18:13:5b:34:b5:cf:d9:d1:47:b2 root@machine3.example.com The key's randomart image is: +--[ DSA 1024]----+ | .. . .| | o . . + | | . .. . E .| | . . o o . . | | + S = . | | + . = o | | + . * . | | . . o . | | .o. . | +-----------------+ Starting sshd. Refer to for more information about fingerprints and SSH. &os; does not install a graphical environment by default. Refer to for more information about installing and configuring a graphical window manager. Proper shutdown of a &os; computer helps protect data and hardware from damage. Do not turn off the power before the system has been properly shut down! If the user is a member of the wheel group, become the superuser by typing su at the command line and entering the root password. Then, type shutdown -p now and the system will shut down cleanly, and if the hardware supports it, turn itself off. Troubleshooting installation troubleshooting This section covers basic installation troubleshooting, such as common problems people have reported. Check the Hardware Notes (http://www.freebsd.org/releases/index.html) document for the version of &os; to make sure the hardware is supported. If the hardware is supported and lock-ups or other problems occur, build a custom kernel using the instructions in to add support for devices which are not present in the GENERIC kernel. The default kernel assumes that most hardware devices are in their factory default configuration in terms of IRQs, I/O addresses, and DMA channels. If the hardware has been reconfigured, a custom kernel configuration file can tell &os; where to find things. Some installation problems can be avoided or alleviated by updating the firmware on various hardware components, most notably the motherboard. Motherboard firmware is usually referred to as the BIOS. Most motherboard and computer manufacturers have a website for upgrades and upgrade information. Manufacturers generally advise against upgrading the motherboard BIOS unless there is a good reason for doing so, like a critical update. The upgrade process can go wrong, leaving the BIOS incomplete and the computer inoperative. If the system hangs while probing hardware during boot, or it behaves strangely during install, ACPI may be the culprit. &os; makes extensive use of the system ACPI service on the &arch.i386;, &arch.amd64;, and ia64 platforms to aid in system configuration if it is detected during boot. Unfortunately, some bugs still exist in both the ACPI driver and within system motherboards and BIOS firmware. ACPI can be disabled by setting the hint.acpi.0.disabled hint in the third stage boot loader: set hint.acpi.0.disabled="1" This is reset each time the system is booted, so it is necessary to add hint.acpi.0.disabled="1" to the file /boot/loader.conf. More information about the boot loader can be found in . Using the Live <acronym>CD</acronym> The welcome menu of bsdinstall, shown in , provides a [ Live CD ] option. This is useful for those who are still wondering whether &os; is the right operating system for them and want to test some of the features before installing. The following points should be noted before using the [ Live CD ]: To gain access to the system, authentication is required. The username is root and the password is blank. As the system runs directly from the installation media, performance will be significantly slower than that of a system installed on a hard disk. This option only provides a command prompt and not a graphical interface. Index: head/en_US.ISO8859-1/books/handbook/chapters.ent =================================================================== --- head/en_US.ISO8859-1/books/handbook/chapters.ent (revision 45601) +++ head/en_US.ISO8859-1/books/handbook/chapters.ent (revision 45602) @@ -1,67 +1,68 @@ %pgpkeys; + "> Index: head/en_US.ISO8859-1/books/handbook/disks/chapter.xml =================================================================== --- head/en_US.ISO8859-1/books/handbook/disks/chapter.xml (revision 45601) +++ head/en_US.ISO8859-1/books/handbook/disks/chapter.xml (revision 45602) @@ -1,3574 +1,3574 @@ Storage Synopsis This chapter covers the use of disks and storage media in &os;. This includes SCSI and IDE disks, CD and DVD media, memory-backed disks, and USB storage devices. After reading this chapter, you will know: How to add additional hard disks to a &os; system. How to grow the size of a disk's partition on &os;. How to configure &os; to use USB storage devices. How to use CD and DVD media on a &os; system. How to use the backup programs available under &os;. How to set up memory disks. What file system snapshots are and how to use them efficiently. How to use quotas to limit disk space usage. How to encrypt disks and swap to secure them against attackers. How to configure a highly available storage network. Before reading this chapter, you should: Know how to configure and install a new &os; kernel. Adding Disks David O'Brien Originally contributed by disks adding This section describes how to add a new SATA disk to a machine that currently only has a single drive. First, turn off the computer and install the drive in the computer following the instructions of the computer, controller, and drive manufacturers. Reboot the system and become root. Inspect /var/run/dmesg.boot to ensure the new disk was found. In this example, the newly added SATA drive will appear as ada1. partitions gpart For this example, a single large partition will be created on the new disk. The GPT partitioning scheme will be used in preference to the older and less versatile MBR scheme. If the disk to be added is not blank, old partition information can be removed with gpart delete. See &man.gpart.8; for details. The partition scheme is created, and then a single partition is added: &prompt.root; gpart create -s GPT ada1 &prompt.root; gpart add -t freebsd-ufs ada1 Depending on use, several smaller partitions may be desired. See &man.gpart.8; for options to create partitions smaller than a whole disk. A file system is created on the new blank disk: &prompt.root; newfs -U /dev/ada1p1 An empty directory is created as a mountpoint, a location for mounting the new disk in the original disk's file system: &prompt.root; mkdir /newdisk Finally, an entry is added to /etc/fstab so the new disk will be mounted automatically at startup: /dev/ada1p1 /newdisk ufs rw 2 2 The new disk can be mounted manually, without restarting the system: &prompt.root; mount /newdisk Resizing and Growing Disks Allan Jude Originally contributed by disks resizing A disk's capacity can increase without any changes to the data already present. This happens commonly with virtual machines, when the virtual disk turns out to be too small and is enlarged. Sometimes a disk image is written to a USB memory stick, but does not use the full capacity. Here we describe how to resize or grow disk contents to take advantage of increased capacity. Determine the device name of the disk to be resized by inspecting /var/run/dmesg.boot. In this example, there is only one SATA disk in the system, so the drive will appear as ada0. partitions gpart List the partitions on the disk to see the current configuration: &prompt.root; gpart show ada0 => 34 83886013 ada0 GPT (48G) [CORRUPT] 34 128 1 freebsd-boot (64k) 162 79691648 2 freebsd-ufs (38G) 79691810 4194236 3 freebsd-swap (2G) 83886046 1 - free - (512B) If the disk was formatted with the GPT partitioning scheme, it may show as corrupted because the GPT backup partition table is no longer at the end of the drive. Fix the backup partition table with gpart: &prompt.root; gpart recover ada0 ada0 recovered Now the additional space on the disk is available for use by a new partition, or an existing partition can be expanded: &prompt.root; gpart show ada0 => 34 102399933 ada0 GPT (48G) 34 128 1 freebsd-boot (64k) 162 79691648 2 freebsd-ufs (38G) 79691810 4194236 3 freebsd-swap (2G) 83886046 18513921 - free - (8.8G) Partitions can only be resized into contiguous free space. Here, the last partition on the disk is the swap partition, but the second partition is the one that needs to be resized. Swap partitions only contain temporary data, so it can safely be unmounted, deleted, and then recreated after resizing other partitions. &prompt.root; swapoff /dev/ada0p3 &prompt.root; gpart delete -i 3 ada0 ada0p3 deleted &prompt.root; gpart show ada0 => 34 102399933 ada0 GPT (48G) 34 128 1 freebsd-boot (64k) 162 79691648 2 freebsd-ufs (38G) 79691810 22708157 - free - (10G) There is risk of data loss when modifying the partition table of a mounted file system. It is best to perform the following steps on an unmounted file system while running from a live CD-ROM or USB device. However, if absolutely necessary, a mounted file system can be resized after disabling GEOM safety features: &prompt.root; sysctl kern.geom.debugflags=16 Resize the partition, leaving room to recreate a swap partition of the desired size. This only modifies the size of the partition. The file system in the partition will be expanded in a separate step. &prompt.root; gpart resize -i 2 -a 4k -s 47G ada0 ada0p2 resized &prompt.root; gpart show ada0 => 34 102399933 ada0 GPT (48G) 34 128 1 freebsd-boot (64k) 162 98566144 2 freebsd-ufs (47G) 98566306 3833661 - free - (1.8G) Recreate the swap partition: &prompt.root; gpart add -t freebsd-swap -a 4k ada0 ada0p3 added &prompt.root; gpart show ada0 => 34 102399933 ada0 GPT (48G) 34 128 1 freebsd-boot (64k) 162 98566144 2 freebsd-ufs (47G) 98566306 3833661 3 freebsd-swap (1.8G) &prompt.root; swapon /dev/ada0p3 Grow the UFS file system to use the new capacity of the resized partition: Growing a live UFS file system is only possible in &os; 10.0-RELEASE and later. For earlier versions, the file system must not be mounted. &prompt.root; growfs /dev/ada0p2 Device is mounted read-write; resizing will result in temporary write suspension for /. It's strongly recommended to make a backup before growing the file system. OK to grow file system on /dev/ada0p2, mounted on /, from 38GB to 47GB? [Yes/No] Yes super-block backups (for fsck -b #) at: 80781312, 82063552, 83345792, 84628032, 85910272, 87192512, 88474752, 89756992, 91039232, 92321472, 93603712, 94885952, 96168192, 97450432 Both the partition and the file system on it have now been resized to use the newly-available disk space. <acronym>USB</acronym> Storage Devices Marc Fonvieille Contributed by USB disks Many external storage solutions, such as hard drives, USB thumbdrives, and CD and DVD burners, use the Universal Serial Bus (USB). &os; provides support for USB 1.x, 2.0, and 3.0 devices. USB 3.0 support is not compatible with some hardware, including Haswell (Lynx point) chipsets. If &os; boots with a failed with error 19 message, disable xHCI/USB3 in the system BIOS. Support for USB storage devices is built into the GENERIC kernel. For a custom kernel, be sure that the following lines are present in the kernel configuration file: device scbus # SCSI bus (required for ATA/SCSI) device da # Direct Access (disks) device pass # Passthrough device (direct ATA/SCSI access) device uhci # provides USB 1.x support device ohci # provides USB 1.x support device ehci # provides USB 2.0 support device xhci # provides USB 3.0 support device usb # USB Bus (required) device umass # Disks/Mass storage - Requires scbus and da device cd # needed for CD and DVD burners &os; uses the &man.umass.4; driver which uses the SCSI subsystem to access USB storage devices. Since any USB device will be seen as a SCSI device by the system, if the USB device is a CD or DVD burner, do not include in a custom kernel configuration file. The rest of this section demonstrates how to verify that a USB storage device is recognized by &os; and how to configure the device so that it can be used. Device Configuration To test the USB configuration, plug in the USB device. Use dmesg to confirm that the drive appears in the system message buffer. It should look something like this: umass0: <STECH Simple Drive, class 0/0, rev 2.00/1.04, addr 3> on usbus0 umass0: SCSI over Bulk-Only; quirks = 0x0100 umass0:4:0:-1: Attached to scbus4 da0 at umass-sim0 bus 0 scbus4 target 0 lun 0 da0: <STECH Simple Drive 1.04> Fixed Direct Access SCSI-4 device da0: Serial Number WD-WXE508CAN263 da0: 40.000MB/s transfers da0: 152627MB (312581808 512 byte sectors: 255H 63S/T 19457C) da0: quirks=0x2<NO_6_BYTE> The brand, device node (da0), speed, and size will differ according to the device. Since the USB device is seen as a SCSI one, camcontrol can be used to list the USB storage devices attached to the system: &prompt.root; camcontrol devlist <STECH Simple Drive 1.04> at scbus4 target 0 lun 0 (pass3,da0) Alternately, usbconfig can be used to list the device. Refer to &man.usbconfig.8; for more information about this command. &prompt.root; usbconfig ugen0.3: <Simple Drive STECH> at usbus0, cfg=0 md=HOST spd=HIGH (480Mbps) pwr=ON (2mA) If the device has not been formatted, refer to for instructions on how to format and create partitions on the USB drive. If the drive comes with a file system, it can be mounted by root using the instructions in . Allowing untrusted users to mount arbitrary media, by enabling vfs.usermount as described below, should not be considered safe from a security point of view. Most file systems were not built to safeguard against malicious devices. To make the device mountable as a normal user, one solution is to make all users of the device a member of the operator group using &man.pw.8;. Next, ensure that operator is able to read and write the device by adding these lines to /etc/devfs.rules: [localrules=5] add path 'da*' mode 0660 group operator If internal SCSI disks are also installed in the system, change the second line as follows: add path 'da[3-9]*' mode 0660 group operator This will exclude the first three SCSI disks (da0 to da2)from belonging to the operator group. Replace 3 with the number of internal SCSI disks. Refer to &man.devfs.rules.5; for more information about this file. Next, enable the ruleset in /etc/rc.conf: devfs_system_ruleset="localrules" Then, instruct the system to allow regular users to mount file systems by adding the following line to /etc/sysctl.conf: vfs.usermount=1 Since this only takes effect after the next reboot, use sysctl to set this variable now: &prompt.root; sysctl vfs.usermount=1 vfs.usermount: 0 -> 1 The final step is to create a directory where the file system is to be mounted. This directory needs to be owned by the user that is to mount the file system. One way to do that is for root to create a subdirectory owned by that user as /mnt/username. In the following example, replace username with the login name of the user and usergroup with the user's primary group: &prompt.root; mkdir /mnt/username &prompt.root; chown username:usergroup /mnt/username Suppose a USB thumbdrive is plugged in, and a device /dev/da0s1 appears. If the device is formatted with a FAT file system, the user can mount it using: &prompt.user; mount -t msdosfs -o -m=644,-M=755 /dev/da0s1 /mnt/username Before the device can be unplugged, it must be unmounted first: &prompt.user; umount /mnt/username After device removal, the system message buffer will show messages similar to the following: umass0: at uhub3, port 2, addr 3 (disconnected) da0 at umass-sim0 bus 0 scbus4 target 0 lun 0 da0: <STECH Simple Drive 1.04> s/n WD-WXE508CAN263 detached (da0:umass-sim0:0:0:0): Periph destroyed Creating and Using <acronym>CD</acronym> Media Mike Meyer Contributed by CD-ROMs creating Compact Disc (CD) media provide a number of features that differentiate them from conventional disks. They are designed so that they can be read continuously without delays to move the head between tracks. While CD media do have tracks, these refer to a section of data to be read continuously, and not a physical property of the disk. The ISO 9660 file system was designed to deal with these differences. ISO 9660 file systems ISO 9660 CD burner ATAPI The &os; Ports Collection provides several utilities for burning and duplicating audio and data CDs. This chapter demonstrates the use of several command line utilities. For CD burning software with a graphical utility, consider installing the sysutils/xcdroast or sysutils/k3b packages or ports. Supported Devices Marc Fonvieille Contributed by CD burner ATAPI/CAM driver The GENERIC kernel provides support for SCSI, USB, and ATAPI CD readers and burners. If a custom kernel is used, the options that need to be present in the kernel configuration file vary by the type of device. For a SCSI burner, make sure these options are present: device scbus # SCSI bus (required for ATA/SCSI) device da # Direct Access (disks) device pass # Passthrough device (direct ATA/SCSI access) device cd # needed for CD and DVD burners For a USB burner, make sure these options are present: device scbus # SCSI bus (required for ATA/SCSI) device da # Direct Access (disks) device pass # Passthrough device (direct ATA/SCSI access) device cd # needed for CD and DVD burners device uhci # provides USB 1.x support device ohci # provides USB 1.x support device ehci # provides USB 2.0 support device xhci # provides USB 3.0 support device usb # USB Bus (required) device umass # Disks/Mass storage - Requires scbus and da For an ATAPI burner, make sure these options are present: device ata # Legacy ATA/SATA controllers device scbus # SCSI bus (required for ATA/SCSI) device pass # Passthrough device (direct ATA/SCSI access) device cd # needed for CD and DVD burners On &os; versions prior to 10.x, this line is also needed in the kernel configuration file if the burner is an ATAPI device: device atapicam Alternately, this driver can be loaded at boot time by adding the following line to /boot/loader.conf: atapicam_load="YES" This will require a reboot of the system as this driver can only be loaded at boot time. To verify that &os; recognizes the device, run dmesg and look for an entry for the device. On systems prior to 10.x, the device name in the first line of the output will be acd0 instead of cd0. &prompt.user; dmesg | grep cd cd0 at ahcich1 bus 0 scbus1 target 0 lun 0 cd0: <HL-DT-ST DVDRAM GU70N LT20> Removable CD-ROM SCSI-0 device cd0: Serial Number M3OD3S34152 cd0: 150.000MB/s transfers (SATA 1.x, UDMA6, ATAPI 12bytes, PIO 8192bytes) cd0: Attempt to query device size failed: NOT READY, Medium not present - tray closed Burning a <acronym>CD</acronym> In &os;, cdrecord can be used to burn CDs. This command is installed with the sysutils/cdrtools package or port. &os; 8.x includes the built-in burncd utility for burning CDs using an ATAPI CD burner. Refer to the manual page for burncd for usage examples. While cdrecord has many options, basic usage is simple. Specify the name of the ISO file to burn and, if the system has multiple burner devices, specify the name of the device to use: &prompt.root; cdrecord dev=device imagefile.iso To determine the device name of the burner, use which might produce results like this: CD-ROMs burning &prompt.root; cdrecord -scanbus ProDVD-ProBD-Clone 3.00 (amd64-unknown-freebsd10.0) Copyright (C) 1995-2010 Jörg Schilling Using libscg version 'schily-0.9' scsibus0: 0,0,0 0) 'SEAGATE ' 'ST39236LW ' '0004' Disk 0,1,0 1) 'SEAGATE ' 'ST39173W ' '5958' Disk 0,2,0 2) * 0,3,0 3) 'iomega ' 'jaz 1GB ' 'J.86' Removable Disk 0,4,0 4) 'NEC ' 'CD-ROM DRIVE:466' '1.26' Removable CD-ROM 0,5,0 5) * 0,6,0 6) * 0,7,0 7) * scsibus1: 1,0,0 100) * 1,1,0 101) * 1,2,0 102) * 1,3,0 103) * 1,4,0 104) * 1,5,0 105) 'YAMAHA ' 'CRW4260 ' '1.0q' Removable CD-ROM 1,6,0 106) 'ARTEC ' 'AM12S ' '1.06' Scanner 1,7,0 107) * Locate the entry for the CD burner and use the three numbers separated by commas as the value for . In this case, the Yamaha burner device is 1,5,0, so the appropriate input to specify that device is . Refer to the manual page for cdrecord for other ways to specify this value and for information on writing audio tracks and controlling the write speed. Alternately, run the following command to get the device address of the burner: &prompt.root; camcontrol devlist <MATSHITA CDRW/DVD UJDA740 1.00> at scbus1 target 0 lun 0 (cd0,pass0) Use the numeric values for scbus, target, and lun. For this example, 1,0,0 is the device name to use. Writing Data to an <acronym>ISO</acronym> File System In order to produce a data CD, the data files that are going to make up the tracks on the CD must be prepared before they can be burned to the CD. In &os;, sysutils/cdrtools installs mkisofs, which can be used to produce an ISO 9660 file system that is an image of a directory tree within a &unix; file system. The simplest usage is to specify the name of the ISO file to create and the path to the files to place into the ISO 9660 file system: &prompt.root; mkisofs -o imagefile.iso /path/to/tree file systems ISO 9660 This command maps the file names in the specified path to names that fit the limitations of the standard ISO 9660 file system, and will exclude files that do not meet the standard for ISO file systems. file systems Joliet A number of options are available to overcome the restrictions imposed by the standard. In particular, enables the Rock Ridge extensions common to &unix; systems and enables Joliet extensions used by µsoft; systems. For CDs that are going to be used only on &os; systems, can be used to disable all filename restrictions. When used with , it produces a file system image that is identical to the specified &os; tree, even if it violates the ISO 9660 standard. CD-ROMs creating bootable The last option of general use is . This is used to specify the location of a boot image for use in producing an El Torito bootable CD. This option takes an argument which is the path to a boot image from the top of the tree being written to the CD. By default, mkisofs creates an ISO image in floppy disk emulation mode, and thus expects the boot image to be exactly 1200, 1440 or 2880 KB in size. Some boot loaders, like the one used by the &os; distribution media, do not use emulation mode. In this case, should be used. So, if /tmp/myboot holds a bootable &os; system with the boot image in /tmp/myboot/boot/cdboot, this command would produce /tmp/bootable.iso: &prompt.root; mkisofs -R -no-emul-boot -b boot/cdboot -o /tmp/bootable.iso /tmp/myboot The resulting ISO image can be mounted as a memory disk with: &prompt.root; mdconfig -a -t vnode -f /tmp/bootable.iso -u 0 &prompt.root; mount -t cd9660 /dev/md0 /mnt One can then verify that /mnt and /tmp/myboot are identical. There are many other options available for mkisofs to fine-tune its behavior. Refer to &man.mkisofs.8; for details. It is possible to copy a data CD to an image file that is functionally equivalent to the image file created with mkisofs. To do so, use dd with the device name as the input file and the name of the ISO to create as the output file: &prompt.root; dd if=/dev/cd0 of=file.iso bs=2048 The resulting image file can be burned to CD as described in . Using Data <acronym>CD</acronym>s Once an ISO has been burned to a CD, it can be mounted by specifying the file system type, the name of the device containing the CD, and an existing mount point: &prompt.root; mount -t cd9660 /dev/cd0 /mnt Since mount assumes that a file system is of type ufs, a Incorrect super block error will occur if -t cd9660 is not included when mounting a data CD. While any data CD can be mounted this way, disks with certain ISO 9660 extensions might behave oddly. For example, Joliet disks store all filenames in two-byte Unicode characters. If some non-English characters show up as question marks, specify the local charset with . For more information, refer to &man.mount.cd9660.8;. In order to do this character conversion with the help of , the kernel requires the cd9660_iconv.ko module to be loaded. This can be done either by adding this line to loader.conf: cd9660_iconv_load="YES" and then rebooting the machine, or by directly loading the module with kldload. Occasionally, Device not configured will be displayed when trying to mount a data CD. This usually means that the CD drive thinks that there is no disk in the tray, or that the drive is not visible on the bus. It can take a couple of seconds for a CD drive to realize that a media is present, so be patient. Sometimes, a SCSI CD drive may be missed because it did not have enough time to answer the bus reset. To resolve this, a custom kernel can be created which increases the default SCSI delay. Add the following option to the custom kernel configuration file and rebuild the kernel using the instructions in : options SCSI_DELAY=15000 This tells the SCSI bus to pause 15 seconds during boot, to give the CD drive every possible chance to answer the bus reset. It is possible to burn a file directly to CD, without creating an ISO 9660 file system. This is known as burning a raw data CD and some people do this for backup purposes. This type of disk can not be mounted as a normal data CD. In order to retrieve the data burned to such a CD, the data must be read from the raw device node. For example, this command will extract a compressed tar file located on the second CD device into the current working directory: &prompt.root; tar xzvf /dev/cd1 In order to mount a data CD, the data must be written using mkisofs. Duplicating Audio <acronym>CD</acronym>s To duplicate an audio CD, extract the audio data from the CD to a series of files, then write these files to a blank CD. describes how to duplicate and burn an audio CD. If the &os; version is less than 10.0 and the device is ATAPI, the module must be first loaded using the instructions in . Duplicating an Audio <acronym>CD</acronym> The sysutils/cdrtools package or port installs cdda2wav. This command can be used to extract all of the audio tracks, with each track written to a separate WAV file in the current working directory: &prompt.user; cdda2wav -vall -B -Owav A device name does not need to be specified if there is only one CD device on the system. Refer to the cdda2wav manual page for instructions on how to specify a device and to learn more about the other options available for this command. Use cdrecord to write the .wav files: &prompt.user; cdrecord -v dev=2,0 -dao -useinfo *.wav Make sure that 2,0 is set appropriately, as described in . Creating and Using <acronym>DVD</acronym> Media Marc Fonvieille Contributed by Andy Polyakov With inputs from DVD burning Compared to the CD, the DVD is the next generation of optical media storage technology. The DVD can hold more data than any CD and is the standard for video publishing. Five physical recordable formats can be defined for a recordable DVD: DVD-R: This was the first DVD recordable format available. The DVD-R standard is defined by the DVD Forum. This format is write once. DVD-RW: This is the rewritable version of the DVD-R standard. A DVD-RW can be rewritten about 1000 times. DVD-RAM: This is a rewritable format which can be seen as a removable hard drive. However, this media is not compatible with most DVD-ROM drives and DVD-Video players as only a few DVD writers support the DVD-RAM format. Refer to for more information on DVD-RAM use. DVD+RW: This is a rewritable format defined by the DVD+RW Alliance. A DVD+RW can be rewritten about 1000 times. DVD+R: This format is the write once variation of the DVD+RW format. A single layer recordable DVD can hold up to 4,700,000,000 bytes which is actually 4.38 GB or 4485 MB as 1 kilobyte is 1024 bytes. A distinction must be made between the physical media and the application. For example, a DVD-Video is a specific file layout that can be written on any recordable DVD physical media such as DVD-R, DVD+R, or DVD-RW. Before choosing the type of media, ensure that both the burner and the DVD-Video player are compatible with the media under consideration. Configuration To perform DVD recording, use &man.growisofs.1;. This command is part of the sysutils/dvd+rw-tools utilities which support all DVD media types. These tools use the SCSI subsystem to access the devices, therefore ATAPI/CAM support must be loaded or statically compiled into the kernel. This support is not needed if the burner uses the USB interface. Refer to for more details on USB device configuration. DMA access must also be enabled for ATAPI devices, by adding the following line to /boot/loader.conf: hw.ata.atapi_dma="1" Before attempting to use dvd+rw-tools, consult the Hardware Compatibility Notes. For a graphical user interface, consider using sysutils/k3b which provides a user friendly interface to &man.growisofs.1; and many other burning tools. Burning Data <acronym>DVD</acronym>s Since &man.growisofs.1; is a front-end to mkisofs, it will invoke &man.mkisofs.8; to create the file system layout and perform the write on the DVD. This means that an image of the data does not need to be created before the burning process. To burn to a DVD+R or a DVD-R the data in /path/to/data, use the following command: &prompt.root; growisofs -dvd-compat -Z /dev/cd0 -J -R /path/to/data In this example, is passed to &man.mkisofs.8; to create an ISO 9660 file system with Joliet and Rock Ridge extensions. Refer to &man.mkisofs.8; for more details. For the initial session recording, is used for both single and multiple sessions. Replace /dev/cd0, with the name of the DVD device. Using indicates that the disk will be closed and that the recording will be unappendable. This should also provide better media compatibility with DVD-ROM drives. To burn a pre-mastered image, such as imagefile.iso, use: &prompt.root; growisofs -dvd-compat -Z /dev/cd0=imagefile.iso The write speed should be detected and automatically set according to the media and the drive being used. To force the write speed, use . Refer to &man.growisofs.1; for example usage. In order to support working files larger than 4.38GB, an UDF/ISO-9660 hybrid file system must be created by passing to &man.mkisofs.8; and all related programs, such as &man.growisofs.1;. This is required only when creating an ISO image file or when writing files directly to a disk. Since a disk created this way must be mounted as an UDF file system with &man.mount.udf.8;, it will be usable only on an UDF aware operating system. Otherwise it will look as if it contains corrupted files. To create this type of ISO file: &prompt.user; mkisofs -R -J -udf -iso-level 3 -o imagefile.iso /path/to/data To burn files directly to a disk: &prompt.root; growisofs -dvd-compat -udf -iso-level 3 -Z /dev/cd0 -J -R /path/to/data When an ISO image already contains large files, no additional options are required for &man.growisofs.1; to burn that image on a disk. Be sure to use an up-to-date version of sysutils/cdrtools, which contains &man.mkisofs.8;, as an older version may not contain large files support. If the latest version does not work, install sysutils/cdrtools-devel and read its &man.mkisofs.8;. Burning a <acronym>DVD</acronym>-Video DVD DVD-Video A DVD-Video is a specific file layout based on the ISO 9660 and micro-UDF (M-UDF) specifications. Since DVD-Video presents a specific data structure hierarchy, a particular program such as multimedia/dvdauthor is needed to author the DVD. If an image of the DVD-Video file system already exists, it can be burned in the same way as any other image. If dvdauthor was used to make the DVD and the result is in /path/to/video, the following command should be used to burn the DVD-Video: &prompt.root; growisofs -Z /dev/cd0 -dvd-video /path/to/video is passed to &man.mkisofs.8; to instruct it to create a DVD-Video file system layout. This option implies the &man.growisofs.1; option. Using a <acronym>DVD+RW</acronym> DVD DVD+RW Unlike CD-RW, a virgin DVD+RW needs to be formatted before first use. It is recommended to let &man.growisofs.1; take care of this automatically whenever appropriate. However, it is possible to use dvd+rw-format to format the DVD+RW: &prompt.root; dvd+rw-format /dev/cd0 Only perform this operation once and keep in mind that only virgin DVD+RW medias need to be formatted. Once formatted, the DVD+RW can be burned as usual. To burn a totally new file system and not just append some data onto a DVD+RW, the media does not need to be blanked first. Instead, write over the previous recording like this: &prompt.root; growisofs -Z /dev/cd0 -J -R /path/to/newdata The DVD+RW format supports appending data to a previous recording. This operation consists of merging a new session to the existing one as it is not considered to be multi-session writing. &man.growisofs.1; will grow the ISO 9660 file system present on the media. For example, to append data to a DVD+RW, use the following: &prompt.root; growisofs -M /dev/cd0 -J -R /path/to/nextdata The same &man.mkisofs.8; options used to burn the initial session should be used during next writes. Use for better media compatibility with DVD-ROM drives. When using DVD+RW, this option will not prevent the addition of data. To blank the media, use: &prompt.root; growisofs -Z /dev/cd0=/dev/zero Using a <acronym>DVD-RW</acronym> DVD DVD-RW A DVD-RW accepts two disc formats: incremental sequential and restricted overwrite. By default, DVD-RW discs are in sequential format. A virgin DVD-RW can be directly written without being formatted. However, a non-virgin DVD-RW in sequential format needs to be blanked before writing a new initial session. To blank a DVD-RW in sequential mode: &prompt.root; dvd+rw-format -blank=full /dev/cd0 A full blanking using will take about one hour on a 1x media. A fast blanking can be performed using , if the DVD-RW will be recorded in Disk-At-Once (DAO) mode. To burn the DVD-RW in DAO mode, use the command: &prompt.root; growisofs -use-the-force-luke=dao -Z /dev/cd0=imagefile.iso Since &man.growisofs.1; automatically attempts to detect fast blanked media and engage DAO write, should not be required. One should instead use restricted overwrite mode with any DVD-RW as this format is more flexible than the default of incremental sequential. To write data on a sequential DVD-RW, use the same instructions as for the other DVD formats: &prompt.root; growisofs -Z /dev/cd0 -J -R /path/to/data To append some data to a previous recording, use with &man.growisofs.1;. However, if data is appended on a DVD-RW in incremental sequential mode, a new session will be created on the disc and the result will be a multi-session disc. A DVD-RW in restricted overwrite format does not need to be blanked before a new initial session. Instead, overwrite the disc with . It is also possible to grow an existing ISO 9660 file system written on the disc with . The result will be a one-session DVD. To put a DVD-RW in restricted overwrite format, the following command must be used: &prompt.root; dvd+rw-format /dev/cd0 To change back to sequential format, use: &prompt.root; dvd+rw-format -blank=full /dev/cd0 Multi-Session Few DVD-ROM drives support multi-session DVDs and most of the time only read the first session. DVD+R, DVD-R and DVD-RW in sequential format can accept multiple sessions. The notion of multiple sessions does not exist for the DVD+RW and the DVD-RW restricted overwrite formats. Using the following command after an initial non-closed session on a DVD+R, DVD-R, or DVD-RW in sequential format, will add a new session to the disc: &prompt.root; growisofs -M /dev/cd0 -J -R /path/to/nextdata Using this command with a DVD+RW or a DVD-RW in restricted overwrite mode will append data while merging the new session to the existing one. The result will be a single-session disc. Use this method to add data after an initial write on these types of media. Since some space on the media is used between each session to mark the end and start of sessions, one should add sessions with a large amount of data to optimize media space. The number of sessions is limited to 154 for a DVD+R, about 2000 for a DVD-R, and 127 for a DVD+R Double Layer. For More Information To obtain more information about a DVD, use dvd+rw-mediainfo /dev/cd0 while the disc in the specified drive. More information about dvd+rw-tools can be found in &man.growisofs.1;, on the dvd+rw-tools web site, and in the cdwrite mailing list archives. When creating a problem report related to the use of dvd+rw-tools, always include the output of dvd+rw-mediainfo. Using a <acronym>DVD-RAM</acronym> DVD DVD-RAM DVD-RAM writers can use either a SCSI or ATAPI interface. For ATAPI devices, DMA access has to be enabled by adding the following line to /boot/loader.conf: hw.ata.atapi_dma="1" A DVD-RAM can be seen as a removable hard drive. Like any other hard drive, the DVD-RAM must be formatted before it can be used. In this example, the whole disk space will be formatted with a standard UFS2 file system: &prompt.root; dd if=/dev/zero of=/dev/acd0 bs=2k count=1 &prompt.root; bsdlabel -Bw acd0 &prompt.root; newfs /dev/acd0 The DVD device, acd0, must be changed according to the configuration. Once the DVD-RAM has been formatted, it can be mounted as a normal hard drive: &prompt.root; mount /dev/acd0 /mnt Once mounted, the DVD-RAM will be both readable and writeable. Creating and Using Floppy Disks This section explains how to format a 3.5 inch floppy disk in &os;. Steps to Format a Floppy A floppy disk needs to be low-level formatted before it can be used. This is usually done by the vendor, but formatting is a good way to check media integrity. To low-level format the floppy disk on &os;, use &man.fdformat.1;. When using this utility, make note of any error messages, as these can help determine if the disk is good or bad. To format the floppy, insert a new 3.5 inch floppy disk into the first floppy drive and issue: &prompt.root; /usr/sbin/fdformat -f 1440 /dev/fd0 After low-level formatting the disk, create a disk label as it is needed by the system to determine the size of the disk and its geometry. The supported geometry values are listed in /etc/disktab. To write the disk label, use &man.bsdlabel.8;: &prompt.root; /sbin/bsdlabel -B -w /dev/fd0 fd1440 The floppy is now ready to be high-level formatted with a file system. The floppy's file system can be either UFS or FAT, where FAT is generally a better choice for floppies. To format the floppy with FAT, issue: &prompt.root; /sbin/newfs_msdos /dev/fd0 The disk is now ready for use. To use the floppy, mount it with &man.mount.msdosfs.8;. One can also install and use emulators/mtools from the Ports Collection. Backup Basics Implementing a backup plan is essential in order to have the ability to recover from disk failure, accidental file deletion, random file corruption, or complete machine destruction, including destruction of on-site backups. The backup type and schedule will vary, depending upon the importance of the data, the granularity needed for file restores, and the amount of acceptable downtime. Some possible backup techniques include: Archives of the whole system, backed up onto permanent, off-site media. This provides protection against all of the problems listed above, but is slow and inconvenient to restore from, especially for non-privileged users. File system snapshots, which are useful for restoring deleted files or previous versions of files. Copies of whole file systems or disks which are sychronized with another system on the network using a scheduled net/rsync. Hardware or software RAID, which minimizes or avoids downtime when a disk fails. Typically, a mix of backup techniques is used. For example, one could create a schedule to automate a weekly, full system backup that is stored off-site and to supplement this backup with hourly ZFS snapshots. In addition, one could make a manual backup of individual directories or files before making file edits or deletions. This section describes some of the utilities which can be used to create and manage backups on a &os; system. File System Backups backup software dump / restore dump restore The traditional &unix; programs for backing up a file system are &man.dump.8;, which creates the backup, and &man.restore.8;, which restores the backup. These utilities work at the disk block level, below the abstractions of the files, links, and directories that are created by file systems. Unlike other backup software, dump backs up an entire file system and is unable to backup only part of a file system or a directory tree that spans multiple file systems. Instead of writing files and directories, dump writes the raw data blocks that comprise files and directories. If dump is used on the root directory, it will not back up /home, /usr or many other directories since these are typically mount points for other file systems or symbolic links into those file systems. When used to restore data, restore stores temporary files in /tmp/ by default. When using a recovery disk with a small /tmp, set TMPDIR to a directory with more free space in order for the restore to succeed. When using dump, be aware that some quirks remain from its early days in Version 6 of AT&T &unix;,circa 1975. The default parameters assume a backup to a 9-track tape, rather than to another type of media or to the high-density tapes available today. These defaults must be overridden on the command line. .rhosts It is possible to backup a file system across the network to a another system or to a tape drive attached to another computer. While the &man.rdump.8; and &man.rrestore.8; utilities can be used for this purpose, they are not considered to be secure. Instead, one can use dump and restore in a more secure fashion over an SSH connection. This example creates a full, compressed backup of the /usr file system and sends the backup file to the specified host over a SSH connection. Using <command>dump</command> over <application>ssh</application> &prompt.root; /sbin/dump -0uan -f - /usr | gzip -2 | ssh -c blowfish \ targetuser@targetmachine.example.com dd of=/mybigfiles/dump-usr-l0.gz This example sets RSH in order to write the backup to a tape drive on a remote system over a SSH connection: Using <command>dump</command> over <application>ssh</application> with <envar>RSH</envar> Set &prompt.root; env RSH=/usr/bin/ssh /sbin/dump -0uan -f targetuser@targetmachine.example.com:/dev/sa0 /usr Directory Backups backup software tar Several built-in utilities are available for backing up and restoring specified files and directories as needed. A good choice for making a backup of all of the files in a directory is &man.tar.1;. This utility dates back to Version 6 of AT&T &unix; and by default assumes a recursive backup to a local tape device. Switches can be used to instead specify the name of a backup file. tar This example creates a compressed backup of the current directory and saves it to /tmp/mybackup.tgz. When creating a backup file, make sure that the backup is not saved to the same directory that is being backed up. Backing Up the Current Directory With <command>tar</command> &prompt.root; tar czvf /tmp/mybackup.tgz . To restore the entire backup, cd into the directory to restore into and specify the name of the backup. Note that this will overwrite any newer versions of files in the restore directory. When in doubt, restore to a temporary directory or specify the name of the file within the backup to restore. Restoring Up the Current Directory With <command>tar</command> &prompt.root; tar xzvf /tmp/mybackup.tgz There are dozens of available switches which are described in &man.tar.1;. This utility also supports the use of exclude patterns to specify which files should not be included when backing up the specified directory or restoring files from a backup. backup software cpio To create a backup using a specified list of files and directories, &man.cpio.1; is a good choice. Unlike tar, cpio does not know how to walk the directory tree and it must be provided the list of files to backup. For example, a list of files can be created using ls or find. This example creates a recursive listing of the current directory which is then piped to cpio in order to create an output backup file named /tmp/mybackup.cpio. Using<command>ls</command> and <command>cpio</command> to Make a Recursive Backup of the Current Directory &prompt.root; ls -R | cpio -ovF /tmp/mybackup.cpio backup software pax pax POSIX IEEE A backup utility which tries to bridge the features provided by tar and cpio is &man.pax.1;. Over the years, the various versions of tar and cpio became slightly incompatible. &posix; created pax which attempts to read and write many of the various cpio and tar formats, plus new formats of its own. The pax equivalent to the previous examples would be: Backing Up the Current Directory With <command>pax</command> &prompt.root; pax -wf /tmp/mybackup.pax . Using Data Tapes for Backups tape media While tape technology has continued to evolve, modern backup systems tend to combine off-site backups with local removable media. &os; supports any tape drive that uses SCSI, such as LTO or DAT. There is limited support for SATA and USB tape drives. For SCSI tape devices, &os; uses the &man.sa.4; driver and the /dev/sa0, /dev/nsa0, and /dev/esa0 devices. The physical device name is /dev/sa0. When /dev/nsa0 is used, the backup application will not rewind the tape after writing a file, which allows writing more than one file to a tape. Using /dev/esa0 ejects the tape after the device is closed. In &os;, mt is used to control operations of the tape drive, such as seeking through files on a tape or writing tape control marks to the tape. For example, the first three files on a tape can be preserved by skipping past them before writing a new file: &prompt.root; mt -f /dev/nsa0 fsf 3 This utility supports many operations. Refer to &man.mt.1; for details. To write a single file to tape using tar, specify the name of the tape device and the file to backup: &prompt.root; tar cvf /dev/sa0 file To recover files from a tar archive on tape into the current directory: &prompt.root; tar xvf /dev/sa0 To backup a UFS file system, use dump. This examples backs up /usr without rewinding the tape when finished: &prompt.root; dump -0aL -b64 -f /dev/nsa0 /usr To interactively restore files from a dump file on tape into the current directory: &prompt.root; restore -i -f /dev/nsa0 Third-Party Backup Utilities backup software The &os; Ports Collection provides many third-party utilities which can be used to schedule the creation of backups, simplify tape backup, and make backups easier and more convenient. Many of these applications are client/server based and can be used to automate the backups of a single system or all of the computers in a network. Popular utilities include Amanda, Bacula, rsync, and duplicity. Emergency Recovery In addition to regular backups, it is recommended to perform the following steps as part of an emergency preparedness plan. bsdlabel Create a print copy of the output of the following commands: gpart show more /etc/fstab dmesg livefs CD Store this printout and a copy of the installation media in a secure location. Should an emergency restore be needed, boot into the installation media and select Live CD to access a rescue shell. This rescue mode can be used to view the current state of the system, and if needed, to reformat disks and restore data from backups. The installation media for &os;/&arch.i386; &rel2.current;-RELEASE does not include a rescue shell. For this version, instead download and burn a Livefs CD image from ftp://ftp.FreeBSD.org/pub/FreeBSD/releases/&arch.i386;/ISO-IMAGES/&rel2.current;/&os;-&rel2.current;-RELEASE-&arch.i386;-livefs.iso. Next, test the rescue shell and the backups. Make notes of the procedure. Store these notes with the media, the printouts, and the backups. These notes may prevent the inadvertent destruction of the backups while under the stress of performing an emergency recovery. For an added measure of security, store the latest backup at a remote location which is physically separated from the computers and disk drives by a significant distance. Memory Disks Marc Fonvieille Reorganized and enhanced by In addition to physical disks, &os; also supports the creation and use of memory disks. One possible use for a memory disk is to access the contents of an ISO file system without the overhead of first burning it to a CD or DVD, then mounting the CD/DVD media. In &os;, the &man.md.4; driver is used to provide support for memory disks. The GENERIC kernel includes this driver. When using a custom kernel configuration file, ensure it includes this line: device md Attaching and Detaching Existing Images disks memory To mount an existing file system image, use mdconfig to specify the name of the ISO file and a free unit number. Then, refer to that unit number to mount it on an existing mount point. Once mounted, the files in the ISO will appear in the mount point. This example attaches diskimage.iso to the memory device /dev/md0 then mounts that memory device on /mnt: &prompt.root; mdconfig -f diskimage.iso -u 0 &prompt.root; mount /dev/md0 /mnt If a unit number is not specified with , mdconfig will automatically allocate an unused memory device and output the name of the allocated unit, such as md4. Refer to &man.mdconfig.8; for more details about this command and its options. disks detaching a memory disk When a memory disk is no longer in use, its resources should be released back to the system. First, unmount the file system, then use mdconfig to detach the disk from the system and release its resources. To continue this example: &prompt.root; umount /mnt &prompt.root; mdconfig -d -u 0 To determine if any memory disks are still attached to the system, type mdconfig -l. Creating a File- or Memory-Backed Memory Disk disks memory file system &os; also supports memory disks where the storage to use is allocated from either a hard disk or an area of memory. The first method is commonly referred to as a file-backed file system and the second method as a memory-backed file system. Both types can be created using mdconfig. To create a new memory-backed file system, specify a type of swap and the size of the memory disk to create. Then, format the memory disk with a file system and mount as usual. This example creates a 5M memory disk on unit 1. That memory disk is then formatted with the UFS file system before it is mounted: &prompt.root; mdconfig -a -t swap -s 5m -u 1 &prompt.root; newfs -U md1 /dev/md1: 5.0MB (10240 sectors) block size 16384, fragment size 2048 using 4 cylinder groups of 1.27MB, 81 blks, 192 inodes. with soft updates super-block backups (for fsck -b #) at: 160, 2752, 5344, 7936 &prompt.root; mount /dev/md1 /mnt &prompt.root; df /mnt Filesystem 1K-blocks Used Avail Capacity Mounted on /dev/md1 4718 4 4338 0% /mnt To create a new file-backed memory disk, first allocate an area of disk to use. This example creates an empty 5K file named newimage: &prompt.root; dd if=/dev/zero of=newimage bs=1k count=5k 5120+0 records in 5120+0 records out Next, attach that file to a memory disk, label the memory disk and format it with the UFS file system, mount the memory disk, and verify the size of the file-backed disk: &prompt.root; mdconfig -f newimage -u 0 &prompt.root; bsdlabel -w md0 auto &prompt.root; newfs md0a /dev/md0a: 5.0MB (10224 sectors) block size 16384, fragment size 2048 using 4 cylinder groups of 1.25MB, 80 blks, 192 inodes. super-block backups (for fsck -b #) at: 160, 2720, 5280, 7840 &prompt.root; mount /dev/md0a /mnt &prompt.root; df /mnt Filesystem 1K-blocks Used Avail Capacity Mounted on /dev/md0a 4710 4 4330 0% /mnt It takes several commands to create a file- or memory-backed file system using mdconfig. &os; also comes with mdmfs which automatically configures a memory disk, formats it with the UFS file system, and mounts it. For example, after creating newimage with dd, this one command is equivalent to running the bsdlabel, newfs, and mount commands shown above: &prompt.root; mdmfs -F newimage -s 5m md0 /mnt To instead create a new memory-based memory disk with mdmfs, use this one command: &prompt.root; mdmfs -s 5m md1 /mnt If the unit number is not specified, mdmfs will automatically select an unused memory device. For more details about mdmfs, refer to &man.mdmfs.8;. File System Snapshots Tom Rhodes Contributed by file systems snapshots &os; offers a feature in conjunction with Soft Updates: file system snapshots. UFS snapshots allow a user to create images of specified file systems, and treat them as a file. Snapshot files must be created in the file system that the action is performed on, and a user may create no more than 20 snapshots per file system. Active snapshots are recorded in the superblock so they are persistent across unmount and remount operations along with system reboots. When a snapshot is no longer required, it can be removed using &man.rm.1;. While snapshots may be removed in any order, all the used space may not be acquired because another snapshot will possibly claim some of the released blocks. The un-alterable file flag is set by &man.mksnap.ffs.8; after initial creation of a snapshot file. &man.unlink.1; makes an exception for snapshot files since it allows them to be removed. Snapshots are created using &man.mount.8;. To place a snapshot of /var in the file /var/snapshot/snap, use the following command: &prompt.root; mount -u -o snapshot /var/snapshot/snap /var Alternatively, use &man.mksnap.ffs.8; to create the snapshot: &prompt.root; mksnap_ffs /var /var/snapshot/snap One can find snapshot files on a file system, such as /var, using &man.find.1;: &prompt.root; find /var -flags snapshot Once a snapshot has been created, it has several uses: Some administrators will use a snapshot file for backup purposes, because the snapshot can be transferred to CDs or tape. The file system integrity checker, &man.fsck.8;, may be run on the snapshot. Assuming that the file system was clean when it was mounted, this should always provide a clean and unchanging result. Running &man.dump.8; on the snapshot will produce a dump file that is consistent with the file system and the timestamp of the snapshot. &man.dump.8; can also take a snapshot, create a dump image, and then remove the snapshot in one command by using . The snapshot can be mounted as a frozen image of the file system. To &man.mount.8; the snapshot /var/snapshot/snap run: &prompt.root; mdconfig -a -t vnode -o readonly -f /var/snapshot/snap -u 4 &prompt.root; mount -r /dev/md4 /mnt The frozen /var is now available through /mnt. Everything will initially be in the same state it was during the snapshot creation time. The only exception is that any earlier snapshots will appear as zero length files. To unmount the snapshot, use: &prompt.root; umount /mnt &prompt.root; mdconfig -d -u 4 For more information about and file system snapshots, including technical papers, visit Marshall Kirk McKusick's website at http://www.mckusick.com/. Disk Quotas accounting disk space disk quotas Disk quotas can be used to limit the amount of disk space or the number of files a user or members of a group may allocate on a per-file system basis. This prevents one user or group of users from consuming all of the available disk space. This section describes how to configure disk quotas for the UFS file system. To configure quotas on the ZFS file system, refer to + linkend="zfs-zfs-quota"/> Enabling Disk Quotas To determine if the &os; kernel provides support for disk quotas: &prompt.user; sysctl kern.features.ufs_quota kern.features.ufs_quota: 1 In this example, the 1 indicates quota support. If the value is instead 0, add the following line to a custom kernel configuration file and rebuild the kernel using the instructions in : options QUOTA Next, enable disk quotas in /etc/rc.conf: quota_enable="YES" disk quotas checking Normally on bootup, the quota integrity of each file system is checked by &man.quotacheck.8;. This program insures that the data in the quota database properly reflects the data on the file system. This is a time consuming process that will significantly affect the time the system takes to boot. To skip this step, add this variable to /etc/rc.conf: check_quotas="NO" Finally, edit /etc/fstab to enable disk quotas on a per-file system basis. To enable per-user quotas on a file system, add to the options field in the /etc/fstab entry for the file system to enable quotas on. For example: /dev/da1s2g /home ufs rw,userquota 1 2 To enable group quotas, use instead. To enable both user and group quotas, separate the options with a comma: /dev/da1s2g /home ufs rw,userquota,groupquota 1 2 By default, quota files are stored in the root directory of the file system as quota.user and quota.group. Refer to &man.fstab.5; for more information. Specifying an alternate location for the quota files is not recommended. Once the configuration is complete, reboot the system and /etc/rc will automatically run the appropriate commands to create the initial quota files for all of the quotas enabled in /etc/fstab. In the normal course of operations, there should be no need to manually run &man.quotacheck.8;, &man.quotaon.8;, or &man.quotaoff.8;. However, one should read these manual pages to be familiar with their operation. Setting Quota Limits disk quotas limits To verify that quotas are enabled, run: &prompt.root; quota -v There should be a one line summary of disk usage and current quota limits for each file system that quotas are enabled on. The system is now ready to be assigned quota limits with edquota. Several options are available to enforce limits on the amount of disk space a user or group may allocate, and how many files they may create. Allocations can be limited based on disk space (block quotas), number of files (inode quotas), or a combination of both. Each limit is further broken down into two categories: hard and soft limits. hard limit A hard limit may not be exceeded. Once a user reaches a hard limit, no further allocations can be made on that file system by that user. For example, if the user has a hard limit of 500 kbytes on a file system and is currently using 490 kbytes, the user can only allocate an additional 10 kbytes. Attempting to allocate an additional 11 kbytes will fail. soft limit Soft limits can be exceeded for a limited amount of time, known as the grace period, which is one week by default. If a user stays over their limit longer than the grace period, the soft limit turns into a hard limit and no further allocations are allowed. When the user drops back below the soft limit, the grace period is reset. In the following example, the quota for the test account is being edited. When edquota is invoked, the editor specified by EDITOR is opened in order to edit the quota limits. The default editor is set to vi. &prompt.root; edquota -u test Quotas for user test: /usr: kbytes in use: 65, limits (soft = 50, hard = 75) inodes in use: 7, limits (soft = 50, hard = 60) /usr/var: kbytes in use: 0, limits (soft = 50, hard = 75) inodes in use: 0, limits (soft = 50, hard = 60) There are normally two lines for each file system that has quotas enabled. One line represents the block limits and the other represents the inode limits. Change the value to modify the quota limit. For example, to raise the block limit on /usr to a soft limit of 500 and a hard limit of 600, change the values in that line as follows: /usr: kbytes in use: 65, limits (soft = 500, hard = 600) The new quota limits take affect upon exiting the editor. Sometimes it is desirable to set quota limits on a range of users. This can be done by first assigning the desired quota limit to a user. Then, use to duplicate that quota to a specified range of user IDs (UIDs). The following command will duplicate those quota limits for UIDs 10,000 through 19,999: &prompt.root; edquota -p test 10000-19999 For more information, refer to &man.edquota.8;. Checking Quota Limits and Disk Usage disk quotas checking To check individual user or group quotas and disk usage, use &man.quota.1;. A user may only examine their own quota and the quota of a group they are a member of. Only the superuser may view all user and group quotas. To get a summary of all quotas and disk usage for file systems with quotas enabled, use &man.repquota.8;. Normally, file systems that the user is not using any disk space on will not show in the output of quota, even if the user has a quota limit assigned for that file system. Use to display those file systems. The following is sample output from quota -v for a user that has quota limits on two file systems. Disk quotas for user test (uid 1002): Filesystem usage quota limit grace files quota limit grace /usr 65* 50 75 5days 7 50 60 /usr/var 0 50 75 0 50 60 grace period In this example, the user is currently 15 kbytes over the soft limit of 50 kbytes on /usr and has 5 days of grace period left. The asterisk * indicates that the user is currently over the quota limit. Quotas over NFS NFS Quotas are enforced by the quota subsystem on the NFS server. The &man.rpc.rquotad.8; daemon makes quota information available to quota on NFS clients, allowing users on those machines to see their quota statistics. On the NFS server, enable rpc.rquotad by removing the # from this line in /etc/inetd.conf: rquotad/1 dgram rpc/udp wait root /usr/libexec/rpc.rquotad rpc.rquotad Then, restart inetd: &prompt.root; service inetd restart Encrypting Disk Partitions Lucky Green Contributed by
shamrock@cypherpunks.to
disks encrypting &os; offers excellent online protections against unauthorized data access. File permissions and Mandatory Access Control (MAC) help prevent unauthorized users from accessing data while the operating system is active and the computer is powered up. However, the permissions enforced by the operating system are irrelevant if an attacker has physical access to a computer and can move the computer's hard drive to another system to copy and analyze the data. Regardless of how an attacker may have come into possession of a hard drive or powered-down computer, the GEOM-based cryptographic subsystems built into &os; are able to protect the data on the computer's file systems against even highly-motivated attackers with significant resources. Unlike encryption methods that encrypt individual files, the built-in gbde and geli utilities can be used to transparently encrypt entire file systems. No cleartext ever touches the hard drive's platter. This chapter demonstrates how to create an encrypted file system on &os;. It first demonstrates the process using gbde and then demonstrates the same example using geli. Disk Encryption with <application>gbde</application> The objective of the &man.gbde.4; facility is to provide a formidable challenge for an attacker to gain access to the contents of a cold storage device. However, if the computer is compromised while up and running and the storage device is actively attached, or the attacker has access to a valid passphrase, it offers no protection to the contents of the storage device. Thus, it is important to provide physical security while the system is running and to protect the passphrase used by the encryption mechanism. This facility provides several barriers to protect the data stored in each disk sector. It encrypts the contents of a disk sector using 128-bit AES in CBC mode. Each sector on the disk is encrypted with a different AES key. For more information on the cryptographic design, including how the sector keys are derived from the user-supplied passphrase, refer to &man.gbde.4;. &os; provides a kernel module for gbde which can be loaded with this command: &prompt.root; kldload geom_bde If using a custom kernel configuration file, ensure it contains this line: options GEOM_BDE The following example demonstrates adding a new hard drive to a system that will hold a single encrypted partition that will be mounted as /private. Encrypting a Partition with <application>gbde</application> Add the New Hard Drive Install the new drive to the system as explained in . For the purposes of this example, a new hard drive partition has been added as /dev/ad4s1c and /dev/ad0s1* represents the existing standard &os; partitions. &prompt.root; ls /dev/ad* /dev/ad0 /dev/ad0s1b /dev/ad0s1e /dev/ad4s1 /dev/ad0s1 /dev/ad0s1c /dev/ad0s1f /dev/ad4s1c /dev/ad0s1a /dev/ad0s1d /dev/ad4 Create a Directory to Hold <command>gbde</command> Lock Files &prompt.root; mkdir /etc/gbde The gbde lock file contains information that gbde requires to access encrypted partitions. Without access to the lock file, gbde will not be able to decrypt the data contained in the encrypted partition without significant manual intervention which is not supported by the software. Each encrypted partition uses a separate lock file. Initialize the <command>gbde</command> Partition A gbde partition must be initialized before it can be used. This initialization needs to be performed only once. This command will open the default editor, in order to set various configuration options in a template. For use with the UFS file system, set the sector_size to 2048: &prompt.root; gbde init /dev/ad4s1c -i -L /etc/gbde/ad4s1c.lock# $FreeBSD: src/sbin/gbde/template.txt,v 1.1.36.1 2009/08/03 08:13:06 kensmith Exp $ # # Sector size is the smallest unit of data which can be read or written. # Making it too small decreases performance and decreases available space. # Making it too large may prevent filesystems from working. 512 is the # minimum and always safe. For UFS, use the fragment size # sector_size = 2048 [...] Once the edit is saved, the user will be asked twice to type the passphrase used to secure the data. The passphrase must be the same both times. The ability of gbde to protect data depends entirely on the quality of the passphrase. For tips on how to select a secure passphrase that is easy to remember, see http://world.std.com/~reinhold/diceware.htm. This initialization creates a lock file for the gbde partition. In this example, it is stored as /etc/gbde/ad4s1c.lock. Lock files must end in .lock in order to be correctly detected by the /etc/rc.d/gbde start up script. Lock files must be backed up together with the contents of any encrypted partitions. Without the lock file, the legitimate owner will be unable to access the data on the encrypted partition. Attach the Encrypted Partition to the Kernel &prompt.root; gbde attach /dev/ad4s1c -l /etc/gbde/ad4s1c.lock This command will prompt to input the passphrase that was selected during the initialization of the encrypted partition. The new encrypted device will appear in /dev as /dev/device_name.bde: &prompt.root; ls /dev/ad* /dev/ad0 /dev/ad0s1b /dev/ad0s1e /dev/ad4s1 /dev/ad0s1 /dev/ad0s1c /dev/ad0s1f /dev/ad4s1c /dev/ad0s1a /dev/ad0s1d /dev/ad4 /dev/ad4s1c.bde Create a File System on the Encrypted Device Once the encrypted device has been attached to the kernel, a file system can be created on the device. This example creates a UFS file system with soft updates enabled. Be sure to specify the partition which has a *.bde extension: &prompt.root; newfs -U /dev/ad4s1c.bde Mount the Encrypted Partition Create a mount point and mount the encrypted file system: &prompt.root; mkdir /private &prompt.root; mount /dev/ad4s1c.bde /private Verify That the Encrypted File System is Available The encrypted file system should now be visible and available for use: &prompt.user; df -H Filesystem Size Used Avail Capacity Mounted on /dev/ad0s1a 1037M 72M 883M 8% / /devfs 1.0K 1.0K 0B 100% /dev /dev/ad0s1f 8.1G 55K 7.5G 0% /home /dev/ad0s1e 1037M 1.1M 953M 0% /tmp /dev/ad0s1d 6.1G 1.9G 3.7G 35% /usr /dev/ad4s1c.bde 150G 4.1K 138G 0% /private After each boot, any encrypted file systems must be manually re-attached to the kernel, checked for errors, and mounted, before the file systems can be used. To configure these steps, add the following lines to /etc/rc.conf: gbde_autoattach_all="YES" gbde_devices="ad4s1c" gbde_lockdir="/etc/gbde" This requires that the passphrase be entered at the console at boot time. After typing the correct passphrase, the encrypted partition will be mounted automatically. Additional gbde boot options are available and listed in &man.rc.conf.5;. sysinstall is incompatible with gbde-encrypted devices. All *.bde devices must be detached from the kernel before starting sysinstall or it will crash during its initial probing for devices. To detach the encrypted device used in the example, use the following command: &prompt.root; gbde detach /dev/ad4s1c Disk Encryption with <command>geli</command> Daniel Gerzo Contributed by An alternative cryptographic GEOM class is available using geli. This control utility adds some features and uses a different scheme for doing cryptographic work. It provides the following features: Utilizes the &man.crypto.9; framework and automatically uses cryptographic hardware when it is available. Supports multiple cryptographic algorithms such as AES, Blowfish, and 3DES. Allows the root partition to be encrypted. The passphrase used to access the encrypted root partition will be requested during system boot. Allows the use of two independent keys. It is fast as it performs simple sector-to-sector encryption. Allows backup and restore of master keys. If a user destroys their keys, it is still possible to get access to the data by restoring keys from the backup. Allows a disk to attach with a random, one-time key which is useful for swap partitions and temporary file systems. More features and usage examples can be found in &man.geli.8;. The following example describes how to generate a key file which will be used as part of the master key for the encrypted provider mounted under /private. The key file will provide some random data used to encrypt the master key. The master key will also be protected by a passphrase. The provider's sector size will be 4kB. The example describes how to attach to the geli provider, create a file system on it, mount it, work with it, and finally, how to detach it. Encrypting a Partition with <command>geli</command> Load <command>geli</command> Support Support for geli is available as a loadable kernel module. To configure the system to automatically load the module at boot time, add the following line to /boot/loader.conf: geom_eli_load="YES" To load the kernel module now: &prompt.root; kldload geom_eli For a custom kernel, ensure the kernel configuration file contains these lines: options GEOM_ELI device crypto Generate the Master Key The following commands generate a master key (/root/da2.key) that is protected with a passphrase. The data source for the key file is /dev/random and the sector size of the provider (/dev/da2.eli) is 4kB as a bigger sector size provides better performance: &prompt.root; dd if=/dev/random of=/root/da2.key bs=64 count=1 &prompt.root; geli init -s 4096 -K /root/da2.key /dev/da2 Enter new passphrase: Reenter new passphrase: It is not mandatory to use both a passphrase and a key file as either method of securing the master key can be used in isolation. If the key file is given as -, standard input will be used. For example, this command generates three key files: &prompt.root; cat keyfile1 keyfile2 keyfile3 | geli init -K - /dev/da2 Attach the Provider with the Generated Key To attach the provider, specify the key file, the name of the disk, and the passphrase: &prompt.root; geli attach -k /root/da2.key /dev/da2 Enter passphrase: This creates a new device with an .eli extension: &prompt.root; ls /dev/da2* /dev/da2 /dev/da2.eli Create the New File System Next, format the device with the UFS file system and mount it on an existing mount point: &prompt.root; dd if=/dev/random of=/dev/da2.eli bs=1m &prompt.root; newfs /dev/da2.eli &prompt.root; mount /dev/da2.eli /private The encrypted file system should now be available for use: &prompt.root; df -H Filesystem Size Used Avail Capacity Mounted on /dev/ad0s1a 248M 89M 139M 38% / /devfs 1.0K 1.0K 0B 100% /dev /dev/ad0s1f 7.7G 2.3G 4.9G 32% /usr /dev/ad0s1d 989M 1.5M 909M 0% /tmp /dev/ad0s1e 3.9G 1.3G 2.3G 35% /var /dev/da2.eli 150G 4.1K 138G 0% /private Once the work on the encrypted partition is done, and the /private partition is no longer needed, it is prudent to put the device into cold storage by unmounting and detaching the geli encrypted partition from the kernel: &prompt.root; umount /private &prompt.root; geli detach da2.eli A rc.d script is provided to simplify the mounting of geli-encrypted devices at boot time. For this example, add these lines to /etc/rc.conf: geli_devices="da2" geli_da2_flags="-p -k /root/da2.key" This configures /dev/da2 as a geli provider with a master key of /root/da2.key. The system will automatically detach the provider from the kernel before the system shuts down. During the startup process, the script will prompt for the passphrase before attaching the provider. Other kernel messages might be shown before and after the password prompt. If the boot process seems to stall, look carefully for the password prompt among the other messages. Once the correct passphrase is entered, the provider is attached. The file system is then mounted, typically by an entry in /etc/fstab. Refer to for instructions on how to configure a file system to mount at boot time. Encrypting Swap Christian Brüffer Written by swap encrypting Like the encryption of disk partitions, encryption of swap space is used to protect sensitive information. Consider an application that deals with passwords. As long as these passwords stay in physical memory, they are not written to disk and will be cleared after a reboot. However, if &os; starts swapping out memory pages to free space, the passwords may be written to the disk unencrypted. Encrypting swap space can be a solution for this scenario. This section demonstrates how to configure an encrypted swap partition using &man.gbde.8; or &man.geli.8; encryption. It assumes a UFS file system where /dev/ad0s1b is the swap partition. Configuring Encrypted Swap Swap partitions are not encrypted by default and should be cleared of any sensitive data before continuing. To overwrite the current swap partition with random garbage, execute the following command: &prompt.root; dd if=/dev/random of=/dev/ad0s1b bs=1m To encrypt the swap partition using &man.gbde.8;, add the .bde suffix to the swap line in /etc/fstab: # Device Mountpoint FStype Options Dump Pass# /dev/ad0s1b.bde none swap sw 0 0 To instead encrypt the swap partition using &man.geli.8;, use the .eli suffix: # Device Mountpoint FStype Options Dump Pass# /dev/ad0s1b.eli none swap sw 0 0 By default, &man.geli.8; uses the AES algorithm with a key length of 128 bit. These defaults can be altered by using geli_swap_flags in /etc/rc.conf. The following flags configure encryption using the Blowfish algorithm with a key length of 128 bits and a sectorsize of 4 kilobytes, and sets detach on last close: geli_swap_flags="-e blowfish -l 128 -s 4096 -d" Refer to the description of onetime in &man.geli.8; for a list of possible options. Encrypted Swap Verification Once the system has rebooted, proper operation of the encrypted swap can be verified using swapinfo. If &man.gbde.8; is being used: &prompt.user; swapinfo Device 1K-blocks Used Avail Capacity /dev/ad0s1b.bde 542720 0 542720 0% If &man.geli.8; is being used: &prompt.user; swapinfo Device 1K-blocks Used Avail Capacity /dev/ad0s1b.eli 542720 0 542720 0% Highly Available Storage (<acronym>HAST</acronym>) Daniel Gerzo Contributed by Freddie Cash With inputs from Pawel Jakub Dawidek Michael W. Lucas Viktor Petersson HAST high availability High availability is one of the main requirements in serious business applications and highly-available storage is a key component in such environments. In &os;, the Highly Available STorage (HAST) framework allows transparent storage of the same data across several physically separated machines connected by a TCP/IP network. HAST can be understood as a network-based RAID1 (mirror), and is similar to the DRBD® storage system used in the GNU/&linux; platform. In combination with other high-availability features of &os; like CARP, HAST makes it possible to build a highly-available storage cluster that is resistant to hardware failures. The following are the main features of HAST: Can be used to mask I/O errors on local hard drives. File system agnostic as it works with any file system supported by &os;. Efficient and quick resynchronization as only the blocks that were modified during the downtime of a node are synchronized. Can be used in an already deployed environment to add additional redundancy. Together with CARP, Heartbeat, or other tools, it can be used to build a robust and durable storage system. After reading this section, you will know: What HAST is, how it works, and which features it provides. How to set up and use HAST on &os;. How to integrate CARP and &man.devd.8; to build a robust storage system. Before reading this section, you should: Understand &unix; and &os; basics (). Know how to configure network interfaces and other core &os; subsystems (). Have a good understanding of &os; networking (). The HAST project was sponsored by The &os; Foundation with support from http://www.omc.net/ and http://www.transip.nl/. HAST Operation HAST provides synchronous block-level replication between two physical machines: the primary, also known as the master node, and the secondary, or slave node. These two machines together are referred to as a cluster. Since HAST works in a primary-secondary configuration, it allows only one of the cluster nodes to be active at any given time. The primary node, also called active, is the one which will handle all the I/O requests to HAST-managed devices. The secondary node is automatically synchronized from the primary node. The physical components of the HAST system are the local disk on primary node, and the disk on the remote, secondary node. HAST operates synchronously on a block level, making it transparent to file systems and applications. HAST provides regular GEOM providers in /dev/hast/ for use by other tools or applications. There is no difference between using HAST-provided devices and raw disks or partitions. Each write, delete, or flush operation is sent to both the local disk and to the remote disk over TCP/IP. Each read operation is served from the local disk, unless the local disk is not up-to-date or an I/O error occurs. In such cases, the read operation is sent to the secondary node. HAST tries to provide fast failure recovery. For this reason, it is important to reduce synchronization time after a node's outage. To provide fast synchronization, HAST manages an on-disk bitmap of dirty extents and only synchronizes those during a regular synchronization, with an exception of the initial sync. There are many ways to handle synchronization. HAST implements several replication modes to handle different synchronization methods: memsync: This mode reports a write operation as completed when the local write operation is finished and when the remote node acknowledges data arrival, but before actually storing the data. The data on the remote node will be stored directly after sending the acknowledgement. This mode is intended to reduce latency, but still provides good reliability. fullsync: This mode reports a write operation as completed when both the local write and the remote write complete. This is the safest and the slowest replication mode. This mode is the default. async: This mode reports a write operation as completed when the local write completes. This is the fastest and the most dangerous replication mode. It should only be used when replicating to a distant node where latency is too high for other modes. HAST Configuration The HAST framework consists of several components: The &man.hastd.8; daemon which provides data synchronization. When this daemon is started, it will automatically load geom_gate.ko. The userland management utility, &man.hastctl.8;. The &man.hast.conf.5; configuration file. This file must exist before starting hastd. Users who prefer to statically build GEOM_GATE support into the kernel should add this line to the custom kernel configuration file, then rebuild the kernel using the instructions in : options GEOM_GATE The following example describes how to configure two nodes in master-slave/primary-secondary operation using HAST to replicate the data between the two. The nodes will be called hasta, with an IP address of 172.16.0.1, and hastb, with an IP address of 172.16.0.2. Both nodes will have a dedicated hard drive /dev/ad6 of the same size for HAST operation. The HAST pool, sometimes referred to as a resource or the GEOM provider in /dev/hast/, will be called test. Configuration of HAST is done using /etc/hast.conf. This file should be identical on both nodes. The simplest configuration is: resource test { on hasta { local /dev/ad6 remote 172.16.0.2 } on hastb { local /dev/ad6 remote 172.16.0.1 } } For more advanced configuration, refer to &man.hast.conf.5;. It is also possible to use host names in the remote statements if the hosts are resolvable and defined either in /etc/hosts or in the local DNS. Once the configuration exists on both nodes, the HAST pool can be created. Run these commands on both nodes to place the initial metadata onto the local disk and to start &man.hastd.8;: &prompt.root; hastctl create test &prompt.root; service hastd onestart It is not possible to use GEOM providers with an existing file system or to convert an existing storage to a HAST-managed pool. This procedure needs to store some metadata on the provider and there will not be enough required space available on an existing provider. A HAST node's primary or secondary role is selected by an administrator, or software like Heartbeat, using &man.hastctl.8;. On the primary node, hasta, issue this command: &prompt.root; hastctl role primary test Run this command on the secondary node, hastb: &prompt.root; hastctl role secondary test Verify the result by running hastctl on each node: &prompt.root; hastctl status test Check the status line in the output. If it says degraded, something is wrong with the configuration file. It should say complete on each node, meaning that the synchronization between the nodes has started. The synchronization completes when hastctl status reports 0 bytes of dirty extents. The next step is to create a file system on the GEOM provider and mount it. This must be done on the primary node. Creating the file system can take a few minutes, depending on the size of the hard drive. This example creates a UFS file system on /dev/hast/test: &prompt.root; newfs -U /dev/hast/test &prompt.root; mkdir /hast/test &prompt.root; mount /dev/hast/test /hast/test Once the HAST framework is configured properly, the final step is to make sure that HAST is started automatically during system boot. Add this line to /etc/rc.conf: hastd_enable="YES" Failover Configuration The goal of this example is to build a robust storage system which is resistant to the failure of any given node. If the primary node fails, the secondary node is there to take over seamlessly, check and mount the file system, and continue to work without missing a single bit of data. To accomplish this task, the Common Address Redundancy Protocol (CARP) is used to provide for automatic failover at the IP layer. CARP allows multiple hosts on the same network segment to share an IP address. Set up CARP on both nodes of the cluster according to the documentation available in . In this example, each node will have its own management IP address and a shared IP address of 172.16.0.254. The primary HAST node of the cluster must be the master CARP node. The HAST pool created in the previous section is now ready to be exported to the other hosts on the network. This can be accomplished by exporting it through NFS or Samba, using the shared IP address 172.16.0.254. The only problem which remains unresolved is an automatic failover should the primary node fail. In the event of CARP interfaces going up or down, the &os; operating system generates a &man.devd.8; event, making it possible to watch for state changes on the CARP interfaces. A state change on the CARP interface is an indication that one of the nodes failed or came back online. These state change events make it possible to run a script which will automatically handle the HAST failover. To catch state changes on the CARP interfaces, add this configuration to /etc/devd.conf on each node: notify 30 { match "system" "IFNET"; match "subsystem" "carp0"; match "type" "LINK_UP"; action "/usr/local/sbin/carp-hast-switch master"; }; notify 30 { match "system" "IFNET"; match "subsystem" "carp0"; match "type" "LINK_DOWN"; action "/usr/local/sbin/carp-hast-switch slave"; }; If the systems are running &os; 10 or higher, replace carp0 with the name of the CARP-configured interface. Restart &man.devd.8; on both nodes to put the new configuration into effect: &prompt.root; service devd restart When the specified interface state changes by going up or down , the system generates a notification, allowing the &man.devd.8; subsystem to run the specified automatic failover script, /usr/local/sbin/carp-hast-switch. For further clarification about this configuration, refer to &man.devd.conf.5;. Here is an example of an automated failover script: #!/bin/sh # Original script by Freddie Cash <fjwcash@gmail.com> # Modified by Michael W. Lucas <mwlucas@BlackHelicopters.org> # and Viktor Petersson <vpetersson@wireload.net> # The names of the HAST resources, as listed in /etc/hast.conf resources="test" # delay in mounting HAST resource after becoming master # make your best guess delay=3 # logging log="local0.debug" name="carp-hast" # end of user configurable stuff case "$1" in master) logger -p $log -t $name "Switching to primary provider for ${resources}." sleep ${delay} # Wait for any "hastd secondary" processes to stop for disk in ${resources}; do while $( pgrep -lf "hastd: ${disk} \(secondary\)" > /dev/null 2>&1 ); do sleep 1 done # Switch role for each disk hastctl role primary ${disk} if [ $? -ne 0 ]; then logger -p $log -t $name "Unable to change role to primary for resource ${disk}." exit 1 fi done # Wait for the /dev/hast/* devices to appear for disk in ${resources}; do for I in $( jot 60 ); do [ -c "/dev/hast/${disk}" ] && break sleep 0.5 done if [ ! -c "/dev/hast/${disk}" ]; then logger -p $log -t $name "GEOM provider /dev/hast/${disk} did not appear." exit 1 fi done logger -p $log -t $name "Role for HAST resources ${resources} switched to primary." logger -p $log -t $name "Mounting disks." for disk in ${resources}; do mkdir -p /hast/${disk} fsck -p -y -t ufs /dev/hast/${disk} mount /dev/hast/${disk} /hast/${disk} done ;; slave) logger -p $log -t $name "Switching to secondary provider for ${resources}." # Switch roles for the HAST resources for disk in ${resources}; do if ! mount | grep -q "^/dev/hast/${disk} on " then else umount -f /hast/${disk} fi sleep $delay hastctl role secondary ${disk} 2>&1 if [ $? -ne 0 ]; then logger -p $log -t $name "Unable to switch role to secondary for resource ${disk}." exit 1 fi logger -p $log -t $name "Role switched to secondary for resource ${disk}." done ;; esac In a nutshell, the script takes these actions when a node becomes master: Promotes the HAST pool to primary on the other node. Checks the file system under the HAST pool. Mounts the pool. When a node becomes secondary: Unmounts the HAST pool. Degrades the HAST pool to secondary. This is just an example script which serves as a proof of concept. It does not handle all the possible scenarios and can be extended or altered in any way, for example, to start or stop required services. For this example, a standard UFS file system was used. To reduce the time needed for recovery, a journal-enabled UFS or ZFS file system can be used instead. More detailed information with additional examples can be found at http://wiki.FreeBSD.org/HAST. Troubleshooting HAST should generally work without issues. However, as with any other software product, there may be times when it does not work as supposed. The sources of the problems may be different, but the rule of thumb is to ensure that the time is synchronized between the nodes of the cluster. When troubleshooting HAST, the debugging level of &man.hastd.8; should be increased by starting hastd with -d. This argument may be specified multiple times to further increase the debugging level. Consider also using -F, which starts hastd in the foreground. Recovering from the Split-brain Condition Split-brain occurs when the nodes of the cluster are unable to communicate with each other, and both are configured as primary. This is a dangerous condition because it allows both nodes to make incompatible changes to the data. This problem must be corrected manually by the system administrator. The administrator must decide which node has more important changes or merge them manually. Then, let HAST perform full synchronization of the node which has the broken data. To do this, issue these commands on the node which needs to be resynchronized: &prompt.root; hastctl role init test &prompt.root; hastctl create test &prompt.root; hastctl role secondary test Index: head/en_US.ISO8859-1/books/handbook/filesystems/chapter.xml =================================================================== --- head/en_US.ISO8859-1/books/handbook/filesystems/chapter.xml (revision 45601) +++ head/en_US.ISO8859-1/books/handbook/filesystems/chapter.xml (revision 45602) @@ -1,853 +1,217 @@ - File Systems Support + Other File Systems TomRhodesWritten by Synopsis File Systems File Systems Support File Systems File systems are an integral part of any operating system. They allow users to upload and store files, provide access to data, and make hard drives useful. Different operating systems differ in their native file system. Traditionally, the native &os; file system has been the Unix File System UFS which has been modernized as UFS2. Since &os; 7.0, the Z File - System ZFS is also available as a native file - system. + System (ZFS) is also available as a native file + system. See for more information. In addition to its native file systems, &os; supports a multitude of other file systems so that data from other operating systems can be accessed locally, such as data stored on locally attached USB storage devices, flash drives, and hard disks. This includes support for the &linux; Extended File System (EXT) and the Reiser file system. There are different levels of &os; support for the various file systems. Some require a kernel module to be loaded and others may require a toolset to be installed. Some non-native file system support is full read-write while others are read-only. After reading this chapter, you will know: The difference between native and supported file systems. Which file systems are supported by &os;. How to enable, configure, access, and make use of non-native file systems. Before reading this chapter, you should: Understand &unix; and &os; basics. Be familiar with the basics of kernel configuration and compilation. Feel comfortable installing software in &os;. Have some familiarity with disks, storage, and device names in &os;. - - - - The Z File System (ZFS) - - The Z file system, originally developed by &sun;, - is designed to use a pooled storage method in that space is only - used as it is needed for data storage. It is also designed for - maximum data integrity, supporting data snapshots, multiple - copies, and data checksums. It uses a software data replication - model, known as RAID-Z. - RAID-Z provides redundancy similar to - hardware RAID, but is designed to prevent - data write corruption and to overcome some of the limitations - of hardware RAID. - - - ZFS Tuning - - Some of the features provided by ZFS - are RAM-intensive, so some tuning may be required to provide - maximum efficiency on systems with limited RAM. - - - Memory - - At a bare minimum, the total system memory should be at - least one gigabyte. The amount of recommended RAM depends - upon the size of the pool and the ZFS features which are - used. A general rule of thumb is 1GB of RAM for every 1TB - of storage. If the deduplication feature is used, a general - rule of thumb is 5GB of RAM per TB of storage to be - deduplicated. While some users successfully use ZFS with - less RAM, it is possible that when the system is under heavy - load, it may panic due to memory exhaustion. Further tuning - may be required for systems with less than the recommended - RAM requirements. - - - - Kernel Configuration - - Due to the RAM limitations of the &i386; platform, users - using ZFS on the &i386; architecture should add the - following option to a custom kernel configuration file, - rebuild the kernel, and reboot: - - options KVA_PAGES=512 - - This option expands the kernel address space, allowing - the vm.kvm_size tunable to be pushed - beyond the currently imposed limit of 1 GB, or the - limit of 2 GB for PAE. To find the - most suitable value for this option, divide the desired - address space in megabytes by four (4). In this example, it - is 512 for 2 GB. - - - - Loader Tunables - - The kmem address space can - be increased on all &os; architectures. On a test system - with one gigabyte of physical memory, success was achieved - with the following options added to - /boot/loader.conf, and the system - restarted: - - vm.kmem_size="330M" -vm.kmem_size_max="330M" -vfs.zfs.arc_max="40M" -vfs.zfs.vdev.cache.size="5M" - - For a more detailed list of recommendations for - ZFS-related tuning, see http://wiki.freebsd.org/ZFSTuningGuide. - - - - - Using <acronym>ZFS</acronym> - - There is a start up mechanism that allows &os; to mount - ZFS pools during system initialization. To - set it, issue the following commands: - - &prompt.root; echo 'zfs_enable="YES"' >> /etc/rc.conf -&prompt.root; service zfs start - - The examples in this section assume three - SCSI disks with the device names - da0, - da1, - and da2. - Users of IDE hardware should instead use - ad - device names. - - - Single Disk Pool - - To create a simple, non-redundant ZFS - pool using a single disk device, use - zpool: - - &prompt.root; zpool create example /dev/da0 - - To view the new pool, review the output of - df: - - &prompt.root; df -Filesystem 1K-blocks Used Avail Capacity Mounted on -/dev/ad0s1a 2026030 235230 1628718 13% / -devfs 1 1 0 100% /dev -/dev/ad0s1d 54098308 1032846 48737598 2% /usr -example 17547136 0 17547136 0% /example - - This output shows that the example - pool has been created and mounted. It - is now accessible as a file system. Files may be created - on it and users can browse it, as seen in the following - example: - - &prompt.root; cd /example -&prompt.root; ls -&prompt.root; touch testfile -&prompt.root; ls -al -total 4 -drwxr-xr-x 2 root wheel 3 Aug 29 23:15 . -drwxr-xr-x 21 root wheel 512 Aug 29 23:12 .. --rw-r--r-- 1 root wheel 0 Aug 29 23:15 testfile - - However, this pool is not taking advantage of any - ZFS features. To create a dataset on - this pool with compression enabled: - - &prompt.root; zfs create example/compressed -&prompt.root; zfs set compression=gzip example/compressed - - The example/compressed dataset is now - a ZFS compressed file system. Try - copying some large files to - /example/compressed. - - Compression can be disabled with: - - &prompt.root; zfs set compression=off example/compressed - - To unmount a file system, issue the following command - and then verify by using df: - - &prompt.root; zfs umount example/compressed -&prompt.root; df -Filesystem 1K-blocks Used Avail Capacity Mounted on -/dev/ad0s1a 2026030 235232 1628716 13% / -devfs 1 1 0 100% /dev -/dev/ad0s1d 54098308 1032864 48737580 2% /usr -example 17547008 0 17547008 0% /example - - To re-mount the file system to make it accessible - again, and verify with df: - - &prompt.root; zfs mount example/compressed -&prompt.root; df -Filesystem 1K-blocks Used Avail Capacity Mounted on -/dev/ad0s1a 2026030 235234 1628714 13% / -devfs 1 1 0 100% /dev -/dev/ad0s1d 54098308 1032864 48737580 2% /usr -example 17547008 0 17547008 0% /example -example/compressed 17547008 0 17547008 0% /example/compressed - - The pool and file system may also be observed by viewing - the output from mount: - - &prompt.root; mount -/dev/ad0s1a on / (ufs, local) -devfs on /dev (devfs, local) -/dev/ad0s1d on /usr (ufs, local, soft-updates) -example on /example (zfs, local) -example/data on /example/data (zfs, local) -example/compressed on /example/compressed (zfs, local) - - ZFS datasets, after creation, may be - used like any file systems. However, many other features - are available which can be set on a per-dataset basis. In - the following example, a new file system, - data is created. Important files will be - stored here, the file system is set to keep two copies of - each data block: - - &prompt.root; zfs create example/data -&prompt.root; zfs set copies=2 example/data - - It is now possible to see the data and space utilization - by issuing df: - - &prompt.root; df -Filesystem 1K-blocks Used Avail Capacity Mounted on -/dev/ad0s1a 2026030 235234 1628714 13% / -devfs 1 1 0 100% /dev -/dev/ad0s1d 54098308 1032864 48737580 2% /usr -example 17547008 0 17547008 0% /example -example/compressed 17547008 0 17547008 0% /example/compressed -example/data 17547008 0 17547008 0% /example/data - - Notice that each file system on the pool has the same - amount of available space. This is the reason for using - df in these examples, to show that the - file systems use only the amount of space they need and all - draw from the same pool. The ZFS file - system does away with concepts such as volumes and - partitions, and allows for several file systems to occupy - the same pool. - - To destroy the file systems and then destroy the pool as - they are no longer needed: - - &prompt.root; zfs destroy example/compressed -&prompt.root; zfs destroy example/data -&prompt.root; zpool destroy example - - - - - <acronym>ZFS</acronym> RAID-Z - - There is no way to prevent a disk from failing. One - method of avoiding data loss due to a failed hard disk is to - implement RAID. ZFS - supports this feature in its pool design. - - To create a RAID-Z pool, issue the - following command and specify the disks to add to the - pool: - - &prompt.root; zpool create storage raidz da0 da1 da2 - - - &sun; recommends that the amount of devices used in - a RAID-Z configuration is between - three and nine. For environments requiring a single pool - consisting of 10 disks or more, consider breaking it up - into smaller RAID-Z groups. If only - two disks are available and redundancy is a requirement, - consider using a ZFS mirror. Refer to - &man.zpool.8; for more details. - - - This command creates the storage - zpool. This may be verified using &man.mount.8; and - &man.df.1;. This command makes a new file system in the - pool called home: - - &prompt.root; zfs create storage/home - - It is now possible to enable compression and keep extra - copies of directories and files using the following - commands: - - &prompt.root; zfs set copies=2 storage/home -&prompt.root; zfs set compression=gzip storage/home - - To make this the new home directory for users, copy the - user data to this directory, and create the appropriate - symbolic links: - - &prompt.root; cp -rp /home/* /storage/home -&prompt.root; rm -rf /home /usr/home -&prompt.root; ln -s /storage/home /home -&prompt.root; ln -s /storage/home /usr/home - - Users should now have their data stored on the freshly - created /storage/home. Test by - adding a new user and logging in as that user. - - Try creating a snapshot which may be rolled back - later: - - &prompt.root; zfs snapshot storage/home@08-30-08 - - Note that the snapshot option will only capture a real - file system, not a home directory or a file. The - @ character is a delimiter used between - the file system name or the volume name. When a user's - home directory gets trashed, restore it with: - - &prompt.root; zfs rollback storage/home@08-30-08 - - To get a list of all available snapshots, run - ls in the file system's - .zfs/snapshot directory. For example, - to see the previously taken snapshot: - - &prompt.root; ls /storage/home/.zfs/snapshot - - It is possible to write a script to perform regular - snapshots on user data. However, over time, snapshots - may consume a great deal of disk space. The previous - snapshot may be removed using the following command: - - &prompt.root; zfs destroy storage/home@08-30-08 - - After testing, /storage/home can be - made the real /home using this - command: - - &prompt.root; zfs set mountpoint=/home storage/home - - Run df and - mount to confirm that the system now - treats the file system as the real - /home: - - &prompt.root; mount -/dev/ad0s1a on / (ufs, local) -devfs on /dev (devfs, local) -/dev/ad0s1d on /usr (ufs, local, soft-updates) -storage on /storage (zfs, local) -storage/home on /home (zfs, local) -&prompt.root; df -Filesystem 1K-blocks Used Avail Capacity Mounted on -/dev/ad0s1a 2026030 235240 1628708 13% / -devfs 1 1 0 100% /dev -/dev/ad0s1d 54098308 1032826 48737618 2% /usr -storage 26320512 0 26320512 0% /storage -storage/home 26320512 0 26320512 0% /home - - This completes the RAID-Z - configuration. To get status updates about the file systems - created during the nightly &man.periodic.8; runs, issue the - following command: - - &prompt.root; echo 'daily_status_zfs_enable="YES"' >> /etc/periodic.conf - - - - Recovering <acronym>RAID</acronym>-Z - - Every software RAID has a method of - monitoring its state. The status of - RAID-Z devices may be viewed with the - following command: - - &prompt.root; zpool status -x - - If all pools are healthy and everything is normal, the - following message will be returned: - - all pools are healthy - - If there is an issue, perhaps a disk has gone offline, - the pool state will look similar to: - - pool: storage - state: DEGRADED -status: One or more devices has been taken offline by the administrator. - Sufficient replicas exist for the pool to continue functioning in a - degraded state. -action: Online the device using 'zpool online' or replace the device with - 'zpool replace'. - scrub: none requested -config: - - NAME STATE READ WRITE CKSUM - storage DEGRADED 0 0 0 - raidz1 DEGRADED 0 0 0 - da0 ONLINE 0 0 0 - da1 OFFLINE 0 0 0 - da2 ONLINE 0 0 0 - -errors: No known data errors - - This indicates that the device was previously taken - offline by the administrator using the following - command: - - &prompt.root; zpool offline storage da1 - - It is now possible to replace - da1 after the system has been - powered down. When the system is back online, the following - command may issued to replace the disk: - - &prompt.root; zpool replace storage da1 - - From here, the status may be checked again, this time - without the flag to get state - information: - - &prompt.root; zpool status storage - pool: storage - state: ONLINE - scrub: resilver completed with 0 errors on Sat Aug 30 19:44:11 2008 -config: - - NAME STATE READ WRITE CKSUM - storage ONLINE 0 0 0 - raidz1 ONLINE 0 0 0 - da0 ONLINE 0 0 0 - da1 ONLINE 0 0 0 - da2 ONLINE 0 0 0 - -errors: No known data errors - - As shown from this example, everything appears to be - normal. - - - - Data Verification - - ZFS uses checksums to verify the - integrity of stored data. These are enabled automatically - upon creation of file systems and may be disabled using the - following command: - - &prompt.root; zfs set checksum=off storage/home - - Doing so is not recommended as - checksums take very little storage space and are used to - check data integrity using checksum verification in a - process is known as scrubbing. To verify the - data integrity of the storage pool, issue - this command: - - &prompt.root; zpool scrub storage - - This process may take considerable time depending on - the amount of data stored. It is also very - I/O intensive, so much so that only one - scrub may be run at any given time. After the scrub has - completed, the status is updated and may be viewed by - issuing a status request: - - &prompt.root; zpool status storage - pool: storage - state: ONLINE - scrub: scrub completed with 0 errors on Sat Jan 26 19:57:37 2013 -config: - - NAME STATE READ WRITE CKSUM - storage ONLINE 0 0 0 - raidz1 ONLINE 0 0 0 - da0 ONLINE 0 0 0 - da1 ONLINE 0 0 0 - da2 ONLINE 0 0 0 - -errors: No known data errors - - The completion time is displayed and helps to ensure - data integrity over a long period of time. - - Refer to &man.zfs.8; and &man.zpool.8; for other - ZFS options. - - - - ZFS Quotas - - ZFS supports different types of quotas: the refquota, - the general quota, the user quota, and the group quota. - This section explains the basics of each type and includes - some usage instructions. - - Quotas limit the amount of space that a dataset and its - descendants can consume, and enforce a limit on the amount - of space used by file systems and snapshots for the - descendants. Quotas are useful to limit the amount of space - a particular user can use. - - - Quotas cannot be set on volumes, as the - volsize property acts as an implicit - quota. - - - The - refquota=size - limits the amount of space a dataset can consume by - enforcing a hard limit on the space used. However, this - hard limit does not include space used by descendants, such - as file systems or snapshots. - - To enforce a general quota of 10 GB for - storage/home/bob, use the - following: - - &prompt.root; zfs set quota=10G storage/home/bob - - User quotas limit the amount of space that can be used - by the specified user. The general format is - userquota@user=size, - and the user's name must be in one of the following - formats: - - - - POSIX compatible name such as - joe. - - - - POSIX numeric ID such as - 789. - - - - SID name - such as - joe.bloggs@example.com. - - - - SID - numeric ID such as - S-1-123-456-789. - - - - For example, to enforce a quota of 50 GB for a user - named joe, use the - following: - - &prompt.root; zfs set userquota@joe=50G - - To remove the quota or make sure that one is not set, - instead use: - - &prompt.root; zfs set userquota@joe=none - - User quota properties are not displayed by - zfs get all. - Non-root users can - only see their own quotas unless they have been granted the - userquota privilege. Users with this - privilege are able to view and set everyone's quota. - - The group quota limits the amount of space that a - specified group can consume. The general format is - groupquota@group=size. - - To set the quota for the group - firstgroup to 50 GB, - use: - - &prompt.root; zfs set groupquota@firstgroup=50G - - To remove the quota for the group - firstgroup, or to make sure that - one is not set, instead use: - - &prompt.root; zfs set groupquota@firstgroup=none - - As with the user quota property, - non-root users can - only see the quotas associated with the groups that they - belong to. However, root or a user with the - groupquota privilege can view and set all - quotas for all groups. - - To display the amount of space consumed by each user on - the specified file system or snapshot, along with any - specified quotas, use zfs userspace. - For group information, use zfs - groupspace. For more information about - supported options or how to display only specific options, - refer to &man.zfs.1;. - - Users with sufficient privileges and root can list the quota for - storage/home/bob using: - - &prompt.root; zfs get quota storage/home/bob - - - - ZFS Reservations - - ZFS supports two types of space reservations. This - section explains the basics of each and includes some usage - instructions. - - The reservation property makes it - possible to reserve a minimum amount of space guaranteed - for a dataset and its descendants. This means that if a - 10 GB reservation is set on - storage/home/bob, if disk - space gets low, at least 10 GB of space is reserved - for this dataset. The refreservation - property sets or indicates the minimum amount of space - guaranteed to a dataset excluding descendants, such as - snapshots. As an example, if a snapshot was taken of - storage/home/bob, enough disk space - would have to exist outside of the - refreservation amount for the operation - to succeed because descendants of the main data set are - not counted by the refreservation - amount and so do not encroach on the space set. - - Reservations of any sort are useful in many situations, - such as planning and testing the suitability of disk space - allocation in a new system, or ensuring that enough space is - available on file systems for system recovery procedures and - files. - - The general format of the reservation - property is - reservation=size, - so to set a reservation of 10 GB on - storage/home/bob, use: - - &prompt.root; zfs set reservation=10G storage/home/bob - - To make sure that no reservation is set, or to remove a - reservation, use: - - &prompt.root; zfs set reservation=none storage/home/bob - - The same principle can be applied to the - refreservation property for setting a - refreservation, with the general format - refreservation=size. - - To check if any reservations or refreservations exist on - storage/home/bob, execute one of the - following commands: - - &prompt.root; zfs get reservation storage/home/bob -&prompt.root; zfs get refreservation storage/home/bob - - &linux; File Systems &os; provides built-in support for several &linux; file systems. This section demonstrates how to load support for and how to mount the supported &linux; file systems. <acronym>ext2</acronym> Kernel support for ext2 file systems has been available since &os; 2.2. In &os; 8.x and earlier, the code is licensed under the GPL. Since &os; 9.0, the code has been rewritten and is now BSD licensed. The &man.ext2fs.5; driver allows the &os; kernel to both read and write to ext2 file systems. This driver can also be used to access ext3 and ext4 file systems. However, ext3 journaling, extended attributes, and inodes greater than 128-bytes are not supported. Support for ext4 is read-only. To access an ext file system, first load the kernel loadable module: &prompt.root; kldload ext2fs Then, mount the ext volume by specifying its &os; partition name and an existing mount point. This example mounts /dev/ad1s1 on /mnt: &prompt.root; mount -t ext2fs /dev/ad1s1 /mnt XFS A &os; kernel can be configured to provide read-only support for XFS file systems. To compile in XFS support, add the following option to a custom kernel configuration file and recompile the kernel using the instructions in : options XFS Then, to mount an XFS volume located on /dev/ad1s1: &prompt.root; mount -t xfs /dev/ad1s1 /mnt The sysutils/xfsprogs package or port provides additional utilities, with man pages, for using, analyzing, and repairing XFS file systems. ReiserFS &os; provides read-only support for The Reiser file system, ReiserFS. To load the &man.reiserfs.5; driver: &prompt.root; kldload reiserfs Then, to mount a ReiserFS volume located on /dev/ad1s1: &prompt.root; mount -t reiserfs /dev/ad1s1 /mnt Index: head/en_US.ISO8859-1/books/handbook/zfs/chapter.xml =================================================================== --- head/en_US.ISO8859-1/books/handbook/zfs/chapter.xml (nonexistent) +++ head/en_US.ISO8859-1/books/handbook/zfs/chapter.xml (revision 45602) @@ -0,0 +1,4332 @@ + + + + + + + The Z File System (<acronym>ZFS</acronym>) + + + + + Tom + Rhodes + + Written by + + + + Allan + Jude + + Written by + + + + Benedict + Reuschling + + Written by + + + + Warren + Block + + Written by + + + + + The Z File System, or + ZFS, is an advanced file system designed to + overcome many of the major problems found in previous + designs. + + Originally developed at &sun;, ongoing open source + ZFS development has moved to the OpenZFS Project. + + ZFS has three major design goals: + + + + Data integrity: All data includes a + checksum of the data. + When data is written, the checksum is calculated and written + along with it. When that data is later read back, the + checksum is calculated again. If the checksums do not match, + a data error has been detected. ZFS will + attempt to automatically correct errors when data redundancy + is available. + + + + Pooled storage: physical storage devices are added to a + pool, and storage space is allocated from that shared pool. + Space is available to all file systems, and can be increased + by adding new storage devices to the pool. + + + + Performance: multiple caching mechanisms provide increased + performance. ARC is an + advanced memory-based read cache. A second level of + disk-based read cache can be added with + L2ARC, and disk-based + synchronous write cache is available with + ZIL. + + + + A complete list of features and terminology is shown in + . + + + What Makes <acronym>ZFS</acronym> Different + + ZFS is significantly different from any + previous file system because it is more than just a file system. + Combining the traditionally separate roles of volume manager and + file system provides ZFS with unique + advantages. The file system is now aware of the underlying + structure of the disks. Traditional file systems could only be + created on a single disk at a time. If there were two disks + then two separate file systems would have to be created. In a + traditional hardware RAID configuration, this + problem was avoided by presenting the operating system with a + single logical disk made up of the space provided by a number of + physical disks, on top of which the operating system placed a + file system. Even in the case of software + RAID solutions like those provided by + GEOM, the UFS file system + living on top of the RAID transform believed + that it was dealing with a single device. + ZFS's combination of the volume manager and + the file system solves this and allows the creation of many file + systems all sharing a pool of available storage. One of the + biggest advantages to ZFS's awareness of the + physical layout of the disks is that existing file systems can + be grown automatically when additional disks are added to the + pool. This new space is then made available to all of the file + systems. ZFS also has a number of different + properties that can be applied to each file system, giving many + advantages to creating a number of different file systems and + datasets rather than a single monolithic file system. + + + + Quick Start Guide + + There is a startup mechanism that allows &os; to mount + ZFS pools during system initialization. To + enable it, add this line to + /etc/rc.conf: + + zfs_enable="YES" + + Then start the service: + + &prompt.root; service zfs start + + The examples in this section assume three + SCSI disks with the device names + da0, + da1, and + da2. Users + of SATA hardware should instead use + ada device + names. + + + Single Disk Pool + + To create a simple, non-redundant pool using a single + disk device: + + &prompt.root; zpool create example /dev/da0 + + To view the new pool, review the output of + df: + + &prompt.root; df +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235230 1628718 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032846 48737598 2% /usr +example 17547136 0 17547136 0% /example + + This output shows that the example pool + has been created and mounted. It is now accessible as a file + system. Files can be created on it and users can browse + it: + + &prompt.root; cd /example +&prompt.root; ls +&prompt.root; touch testfile +&prompt.root; ls -al +total 4 +drwxr-xr-x 2 root wheel 3 Aug 29 23:15 . +drwxr-xr-x 21 root wheel 512 Aug 29 23:12 .. +-rw-r--r-- 1 root wheel 0 Aug 29 23:15 testfile + + However, this pool is not taking advantage of any + ZFS features. To create a dataset on this + pool with compression enabled: + + &prompt.root; zfs create example/compressed +&prompt.root; zfs set compression=gzip example/compressed + + The example/compressed dataset is now a + ZFS compressed file system. Try copying + some large files to + /example/compressed. + + Compression can be disabled with: + + &prompt.root; zfs set compression=off example/compressed + + To unmount a file system, use + zfs umount and then verify with + df: + + &prompt.root; zfs umount example/compressed +&prompt.root; df +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235232 1628716 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032864 48737580 2% /usr +example 17547008 0 17547008 0% /example + + To re-mount the file system to make it accessible again, + use zfs mount and verify with + df: + + &prompt.root; zfs mount example/compressed +&prompt.root; df +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235234 1628714 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032864 48737580 2% /usr +example 17547008 0 17547008 0% /example +example/compressed 17547008 0 17547008 0% /example/compressed + + The pool and file system may also be observed by viewing + the output from mount: + + &prompt.root; mount +/dev/ad0s1a on / (ufs, local) +devfs on /dev (devfs, local) +/dev/ad0s1d on /usr (ufs, local, soft-updates) +example on /example (zfs, local) +example/data on /example/data (zfs, local) +example/compressed on /example/compressed (zfs, local) + + After creation, ZFS datasets can be + used like any file systems. However, many other features are + available which can be set on a per-dataset basis. In the + example below, a new file system called + data is created. Important files will be + stored here, so it is configured to keep two copies of each + data block: + + &prompt.root; zfs create example/data +&prompt.root; zfs set copies=2 example/data + + It is now possible to see the data and space utilization + by issuing df: + + &prompt.root; df +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235234 1628714 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032864 48737580 2% /usr +example 17547008 0 17547008 0% /example +example/compressed 17547008 0 17547008 0% /example/compressed +example/data 17547008 0 17547008 0% /example/data + + Notice that each file system on the pool has the same + amount of available space. This is the reason for using + df in these examples, to show that the file + systems use only the amount of space they need and all draw + from the same pool. ZFS eliminates + concepts such as volumes and partitions, and allows multiple + file systems to occupy the same pool. + + To destroy the file systems and then destroy the pool as + it is no longer needed: + + &prompt.root; zfs destroy example/compressed +&prompt.root; zfs destroy example/data +&prompt.root; zpool destroy example + + + + RAID-Z + + Disks fail. One method of avoiding data loss from disk + failure is to implement RAID. + ZFS supports this feature in its pool + design. RAID-Z pools require three or more + disks but provide more usable space than mirrored + pools. + + This example creates a RAID-Z pool, + specifying the disks to add to the pool: + + &prompt.root; zpool create storage raidz da0 da1 da2 + + + &sun; recommends that the number of devices used in a + RAID-Z configuration be between three and + nine. For environments requiring a single pool consisting + of 10 disks or more, consider breaking it up into smaller + RAID-Z groups. If only two disks are + available and redundancy is a requirement, consider using a + ZFS mirror. Refer to &man.zpool.8; for + more details. + + + The previous example created the + storage zpool. This example makes a new + file system called home in that + pool: + + &prompt.root; zfs create storage/home + + Compression and keeping extra copies of directories + and files can be enabled: + + &prompt.root; zfs set copies=2 storage/home +&prompt.root; zfs set compression=gzip storage/home + + To make this the new home directory for users, copy the + user data to this directory and create the appropriate + symbolic links: + + &prompt.root; cp -rp /home/* /storage/home +&prompt.root; rm -rf /home /usr/home +&prompt.root; ln -s /storage/home /home +&prompt.root; ln -s /storage/home /usr/home + + Users data is now stored on the freshly-created + /storage/home. Test by adding a new user + and logging in as that user. + + Try creating a file system snapshot which can be rolled + back later: + + &prompt.root; zfs snapshot storage/home@08-30-08 + + Snapshots can only be made of a full file system, not a + single directory or file. + + The @ character is a delimiter between + the file system name or the volume name. If an important + directory has been accidentally deleted, the file system can + be backed up, then rolled back to an earlier snapshot when the + directory still existed: + + &prompt.root; zfs rollback storage/home@08-30-08 + + To list all available snapshots, run + ls in the file system's + .zfs/snapshot directory. For example, to + see the previously taken snapshot: + + &prompt.root; ls /storage/home/.zfs/snapshot + + It is possible to write a script to perform regular + snapshots on user data. However, over time, snapshots can + consume a great deal of disk space. The previous snapshot can + be removed using the command: + + &prompt.root; zfs destroy storage/home@08-30-08 + + After testing, /storage/home can be + made the real /home using this + command: + + &prompt.root; zfs set mountpoint=/home storage/home + + Run df and mount to + confirm that the system now treats the file system as the real + /home: + + &prompt.root; mount +/dev/ad0s1a on / (ufs, local) +devfs on /dev (devfs, local) +/dev/ad0s1d on /usr (ufs, local, soft-updates) +storage on /storage (zfs, local) +storage/home on /home (zfs, local) +&prompt.root; df +Filesystem 1K-blocks Used Avail Capacity Mounted on +/dev/ad0s1a 2026030 235240 1628708 13% / +devfs 1 1 0 100% /dev +/dev/ad0s1d 54098308 1032826 48737618 2% /usr +storage 26320512 0 26320512 0% /storage +storage/home 26320512 0 26320512 0% /home + + This completes the RAID-Z + configuration. Daily status updates about the file systems + created can be generated as part of the nightly + &man.periodic.8; runs. Add this line to + /etc/periodic.conf: + + daily_status_zfs_enable="YES" + + + + Recovering <acronym>RAID-Z</acronym> + + Every software RAID has a method of + monitoring its state. The status of + RAID-Z devices may be viewed with this + command: + + &prompt.root; zpool status -x + + If all pools are + Online and everything + is normal, the message shows: + + all pools are healthy + + If there is an issue, perhaps a disk is in the + Offline state, the + pool state will look similar to: + + pool: storage + state: DEGRADED +status: One or more devices has been taken offline by the administrator. + Sufficient replicas exist for the pool to continue functioning in a + degraded state. +action: Online the device using 'zpool online' or replace the device with + 'zpool replace'. + scrub: none requested +config: + + NAME STATE READ WRITE CKSUM + storage DEGRADED 0 0 0 + raidz1 DEGRADED 0 0 0 + da0 ONLINE 0 0 0 + da1 OFFLINE 0 0 0 + da2 ONLINE 0 0 0 + +errors: No known data errors + + This indicates that the device was previously taken + offline by the administrator with this command: + + &prompt.root; zpool offline storage da1 + + Now the system can be powered down to replace + da1. When the system is back online, + the failed disk can replaced in the pool: + + &prompt.root; zpool replace storage da1 + + From here, the status may be checked again, this time + without so that all pools are + shown: + + &prompt.root; zpool status storage + pool: storage + state: ONLINE + scrub: resilver completed with 0 errors on Sat Aug 30 19:44:11 2008 +config: + + NAME STATE READ WRITE CKSUM + storage ONLINE 0 0 0 + raidz1 ONLINE 0 0 0 + da0 ONLINE 0 0 0 + da1 ONLINE 0 0 0 + da2 ONLINE 0 0 0 + +errors: No known data errors + + In this example, everything is normal. + + + + Data Verification + + ZFS uses checksums to verify the + integrity of stored data. These are enabled automatically + upon creation of file systems. + + + Checksums can be disabled, but it is + not recommended! Checksums take very + little storage space and provide data integrity. Many + ZFS features will not work properly with + checksums disabled. There is no noticeable performance gain + from disabling these checksums. + + + Checksum verification is known as + scrubbing. Verify the data integrity of + the storage pool with this command: + + &prompt.root; zpool scrub storage + + The duration of a scrub depends on the amount of data + stored. Larger amounts of data will take proportionally + longer to verify. Scrubs are very I/O + intensive, and only one scrub is allowed to run at a time. + After the scrub completes, the status can be viewed with + status: + + &prompt.root; zpool status storage + pool: storage + state: ONLINE + scrub: scrub completed with 0 errors on Sat Jan 26 19:57:37 2013 +config: + + NAME STATE READ WRITE CKSUM + storage ONLINE 0 0 0 + raidz1 ONLINE 0 0 0 + da0 ONLINE 0 0 0 + da1 ONLINE 0 0 0 + da2 ONLINE 0 0 0 + +errors: No known data errors + + The completion date of the last scrub operation is + displayed to help track when another scrub is required. + Routine scrubs help protect data from silent corruption and + ensure the integrity of the pool. + + Refer to &man.zfs.8; and &man.zpool.8; for other + ZFS options. + + + + + <command>zpool</command> Administration + + ZFS administration is divided between two + main utilities. The zpool utility controls + the operation of the pool and deals with adding, removing, + replacing, and managing disks. The + zfs utility + deals with creating, destroying, and managing datasets, + both file systems and + volumes. + + + Creating and Destroying Storage Pools + + Creating a ZFS storage pool + (zpool) involves making a number of + decisions that are relatively permanent because the structure + of the pool cannot be changed after the pool has been created. + The most important decision is what types of vdevs into which + to group the physical disks. See the list of + vdev types for details + about the possible options. After the pool has been created, + most vdev types do not allow additional disks to be added to + the vdev. The exceptions are mirrors, which allow additional + disks to be added to the vdev, and stripes, which can be + upgraded to mirrors by attaching an additional disk to the + vdev. Although additional vdevs can be added to expand a + pool, the layout of the pool cannot be changed after pool + creation. Instead, the data must be backed up and the + pool destroyed and recreated. + + Create a simple mirror pool: + + &prompt.root; zpool create mypool mirror /dev/ada1 /dev/ada2 +&prompt.root; zpool status + pool: mypool + state: ONLINE + scan: none requested +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada1 ONLINE 0 0 0 + ada2 ONLINE 0 0 0 + +errors: No known data errors + + Multiple vdevs can be created at once. Specify multiple + groups of disks separated by the vdev type keyword, + mirror in this example: + + &prompt.root; zpool create mypool mirror /dev/ada1 /dev/ada2 mirror /dev/ada3 /dev/ada4 + pool: mypool + state: ONLINE + scan: none requested +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada1 ONLINE 0 0 0 + ada2 ONLINE 0 0 0 + mirror-1 ONLINE 0 0 0 + ada3 ONLINE 0 0 0 + ada4 ONLINE 0 0 0 + +errors: No known data errors + + Pools can also be constructed using partitions rather than + whole disks. Putting ZFS in a separate + partition allows the same disk to have other partitions for + other purposes. In particular, partitions with bootcode and + file systems needed for booting can be added. This allows + booting from disks that are also members of a pool. There is + no performance penalty on &os; when using a partition rather + than a whole disk. Using partitions also allows the + administrator to under-provision the + disks, using less than the full capacity. If a future + replacement disk of the same nominal size as the original + actually has a slightly smaller capacity, the smaller + partition will still fit, and the replacement disk can still + be used. + + Create a + RAID-Z2 pool using + partitions: + + &prompt.root; zpool create mypool raidz2 /dev/ada0p3 /dev/ada1p3 /dev/ada2p3 /dev/ada3p3 /dev/ada4p3 /dev/ada5p3 +&prompt.root; zpool status + pool: mypool + state: ONLINE + scan: none requested +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + raidz2-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + ada2p3 ONLINE 0 0 0 + ada3p3 ONLINE 0 0 0 + ada4p3 ONLINE 0 0 0 + ada5p3 ONLINE 0 0 0 + +errors: No known data errors + + A pool that is no longer needed can be destroyed so that + the disks can be reused. Destroying a pool involves first + unmounting all of the datasets in that pool. If the datasets + are in use, the unmount operation will fail and the pool will + not be destroyed. The destruction of the pool can be forced + with , but this can cause undefined + behavior in applications which had open files on those + datasets. + + + + Adding and Removing Devices + + There are two cases for adding disks to a zpool: attaching + a disk to an existing vdev with + zpool attach, or adding vdevs to the pool + with zpool add. Only some + vdev types allow disks to + be added to the vdev after creation. + + A pool created with a single disk lacks redundancy. + Corruption can be detected but + not repaired, because there is no other copy of the data. + + The copies property may + be able to recover from a small failure such as a bad sector, + but does not provide the same level of protection as mirroring + or RAID-Z. Starting with a pool consisting + of a single disk vdev, zpool attach can be + used to add an additional disk to the vdev, creating a mirror. + zpool attach can also be used to add + additional disks to a mirror group, increasing redundancy and + read performance. If the disks being used for the pool are + partitioned, replicate the layout of the first disk on to the + second, gpart backup and + gpart restore can be used to make this + process easier. + + Upgrade the single disk (stripe) vdev + ada0p3 to a mirror by attaching + ada1p3: + + &prompt.root; zpool status + pool: mypool + state: ONLINE + scan: none requested +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + +errors: No known data errors +&prompt.root; zpool attach mypool ada0p3 ada1p3 +Make sure to wait until resilver is done before rebooting. + +If you boot from pool 'mypool', you may need to update +boot code on newly attached disk 'ada1p3'. + +Assuming you use GPT partitioning and 'da0' is your new boot disk +you may use the following command: + + gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 da0 +&prompt.root; gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada1 +bootcode written to ada1 +&prompt.root; zpool status + pool: mypool + state: ONLINE +status: One or more devices is currently being resilvered. The pool will + continue to function, possibly in a degraded state. +action: Wait for the resilver to complete. + scan: resilver in progress since Fri May 30 08:19:19 2014 + 527M scanned out of 781M at 47.9M/s, 0h0m to go + 527M resilvered, 67.53% done +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 (resilvering) + +errors: No known data errors +&prompt.root; zpool status + pool: mypool + state: ONLINE + scan: resilvered 781M in 0h0m with 0 errors on Fri May 30 08:15:58 2014 +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + +errors: No known data errors + + When adding disks to the existing vdev is not an option, + as for RAID-Z, an alternative method is to + add another vdev to the pool. Additional vdevs provide higher + performance, distributing writes across the vdevs. Each vdev + is reponsible for providing its own redundancy. It is + possible, but discouraged, to mix vdev types, like + mirror and RAID-Z. + Adding a non-redundant vdev to a pool containing mirror or + RAID-Z vdevs risks the data on the entire + pool. Writes are distributed, so the failure of the + non-redundant disk will result in the loss of a fraction of + every block that has been written to the pool. + + Data is striped across each of the vdevs. For example, + with two mirror vdevs, this is effectively a + RAID 10 that stripes writes across two sets + of mirrors. Space is allocated so that each vdev reaches 100% + full at the same time. There is a performance penalty if the + vdevs have different amounts of free space, as a + disproportionate amount of the data is written to the less + full vdev. + + When attaching additional devices to a boot pool, remember + to update the bootcode. + + Attach a second mirror group (ada2p3 + and ada3p3) to the existing + mirror: + + &prompt.root; zpool status + pool: mypool + state: ONLINE + scan: resilvered 781M in 0h0m with 0 errors on Fri May 30 08:19:35 2014 +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + +errors: No known data errors +&prompt.root; zpool add mypool mirror ada2p3 ada3p3 +&prompt.root; gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada2 +bootcode written to ada2 +&prompt.root; gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada3 +bootcode written to ada3 +&prompt.root; zpool status + pool: mypool + state: ONLINE + scan: scrub repaired 0 in 0h0m with 0 errors on Fri May 30 08:29:51 2014 +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + mirror-1 ONLINE 0 0 0 + ada2p3 ONLINE 0 0 0 + ada3p3 ONLINE 0 0 0 + +errors: No known data errors + + Currently, vdevs cannot be removed from a pool, and disks + can only be removed from a mirror if there is enough remaining + redundancy. If only one disk in a mirror group remains, it + ceases to be a mirror and reverts to being a stripe, risking + the entire pool if that remaining disk fails. + + Remove a disk from a three-way mirror group: + + &prompt.root; zpool status + pool: mypool + state: ONLINE + scan: scrub repaired 0 in 0h0m with 0 errors on Fri May 30 08:29:51 2014 +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + ada2p3 ONLINE 0 0 0 + +errors: No known data errors +&prompt.root; zpool detach mypool ada2p3 +&prompt.root; zpool status + pool: mypool + state: ONLINE + scan: scrub repaired 0 in 0h0m with 0 errors on Fri May 30 08:29:51 2014 +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + +errors: No known data errors + + + + Checking the Status of a Pool + + Pool status is important. If a drive goes offline or a + read, write, or checksum error is detected, the corresponding + error count increases. The status output + shows the configuration and status of each device in the pool + and the status of the entire pool. Actions that need to be + taken and details about the last scrub + are also shown. + + &prompt.root; zpool status + pool: mypool + state: ONLINE + scan: scrub repaired 0 in 2h25m with 0 errors on Sat Sep 14 04:25:50 2013 +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + raidz2-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + ada2p3 ONLINE 0 0 0 + ada3p3 ONLINE 0 0 0 + ada4p3 ONLINE 0 0 0 + ada5p3 ONLINE 0 0 0 + +errors: No known data errors + + + + Clearing Errors + + When an error is detected, the read, write, or checksum + counts are incremented. The error message can be cleared and + the counts reset with zpool clear + mypool. Clearing the + error state can be important for automated scripts that alert + the administrator when the pool encounters an error. Further + errors may not be reported if the old errors are not + cleared. + + + + Replacing a Functioning Device + + There are a number of situations where it m be + desirable to replace one disk with a different disk. When + replacing a working disk, the process keeps the old disk + online during the replacement. The pool never enters a + degraded state, + reducing the risk of data loss. + zpool replace copies all of the data from + the old disk to the new one. After the operation completes, + the old disk is disconnected from the vdev. If the new disk + is larger than the old disk, it may be possible to grow the + zpool, using the new space. See Growing a Pool. + + Replace a functioning device in the pool: + + &prompt.root; zpool status + pool: mypool + state: ONLINE + scan: none requested +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + +errors: No known data errors +&prompt.root; zpool replace mypool ada1p3 ada2p3 +Make sure to wait until resilver is done before rebooting. + +If you boot from pool 'zroot', you may need to update +boot code on newly attached disk 'ada2p3'. + +Assuming you use GPT partitioning and 'da0' is your new boot disk +you may use the following command: + + gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 da0 +&prompt.root; gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada2 +&prompt.root; zpool status + pool: mypool + state: ONLINE +status: One or more devices is currently being resilvered. The pool will + continue to function, possibly in a degraded state. +action: Wait for the resilver to complete. + scan: resilver in progress since Mon Jun 2 14:21:35 2014 + 604M scanned out of 781M at 46.5M/s, 0h0m to go + 604M resilvered, 77.39% done +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + replacing-1 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + ada2p3 ONLINE 0 0 0 (resilvering) + +errors: No known data errors +&prompt.root; zpool status + pool: mypool + state: ONLINE + scan: resilvered 781M in 0h0m with 0 errors on Mon Jun 2 14:21:52 2014 +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada2p3 ONLINE 0 0 0 + +errors: No known data errors + + + + Dealing with Failed Devices + + When a disk in a pool fails, the vdev to which the disk + belongs enters the + degraded state. All + of the data is still available, but performance may be reduced + because missing data must be calculated from the available + redundancy. To restore the vdev to a fully functional state, + the failed physical device must be replaced. + ZFS is then instructed to begin the + resilver operation. + Data that was on the failed device is recalculated from + available redundancy and written to the replacement device. + After completion, the vdev returns to + online status. + + If the vdev does not have any redundancy, or if multiple + devices have failed and there is not enough redundancy to + compensate, the pool enters the + faulted state. If a + sufficient number of devices cannot be reconnected to the + pool, the pool becomes inoperative and data must be restored + from backups. + + When replacing a failed disk, the name of the failed disk + is replaced with the GUID of the device. + A new device name parameter for + zpool replace is not required if the + replacement device has the same device name. + + Replace a failed disk using + zpool replace: + + &prompt.root; zpool status + pool: mypool + state: DEGRADED +status: One or more devices could not be opened. Sufficient replicas exist for + the pool to continue functioning in a degraded state. +action: Attach the missing device and online it using 'zpool online'. + see: http://illumos.org/msg/ZFS-8000-2Q + scan: none requested +config: + + NAME STATE READ WRITE CKSUM + mypool DEGRADED 0 0 0 + mirror-0 DEGRADED 0 0 0 + ada0p3 ONLINE 0 0 0 + 316502962686821739 UNAVAIL 0 0 0 was /dev/ada1p3 + +errors: No known data errors +&prompt.root; zpool replace mypool 316502962686821739 ada2p3 +&prompt.root; zpool status + pool: mypool + state: DEGRADED +status: One or more devices is currently being resilvered. The pool will + continue to function, possibly in a degraded state. +action: Wait for the resilver to complete. + scan: resilver in progress since Mon Jun 2 14:52:21 2014 + 641M scanned out of 781M at 49.3M/s, 0h0m to go + 640M resilvered, 82.04% done +config: + + NAME STATE READ WRITE CKSUM + mypool DEGRADED 0 0 0 + mirror-0 DEGRADED 0 0 0 + ada0p3 ONLINE 0 0 0 + replacing-1 UNAVAIL 0 0 0 + 15732067398082357289 UNAVAIL 0 0 0 was /dev/ada1p3/old + ada2p3 ONLINE 0 0 0 (resilvering) + +errors: No known data errors +&prompt.root; zpool status + pool: mypool + state: ONLINE + scan: resilvered 781M in 0h0m with 0 errors on Mon Jun 2 14:52:38 2014 +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada2p3 ONLINE 0 0 0 + +errors: No known data errors + + + + Scrubbing a Pool + + It is recommended that pools be + scrubbed regularly, + ideally at least once every month. The + scrub operation is very disk-intensive and + will reduce performance while running. Avoid high-demand + periods when scheduling scrub or use vfs.zfs.scrub_delay + to adjust the relative priority of the + scrub to prevent it interfering with other + workloads. + + &prompt.root; zpool scrub mypool +&prompt.root; zpool status + pool: mypool + state: ONLINE + scan: scrub in progress since Wed Feb 19 20:52:54 2014 + 116G scanned out of 8.60T at 649M/s, 3h48m to go + 0 repaired, 1.32% done +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + raidz2-0 ONLINE 0 0 0 + ada0p3 ONLINE 0 0 0 + ada1p3 ONLINE 0 0 0 + ada2p3 ONLINE 0 0 0 + ada3p3 ONLINE 0 0 0 + ada4p3 ONLINE 0 0 0 + ada5p3 ONLINE 0 0 0 + +errors: No known data errors + + In the event that a scrub operation needs to be cancelled, + issue zpool scrub -s + mypool. + + + + Self-Healing + + The checksums stored with data blocks enable the file + system to self-heal. This feature will + automatically repair data whose checksum does not match the + one recorded on another device that is part of the storage + pool. For example, a mirror with two disks where one drive is + starting to malfunction and cannot properly store the data any + more. This is even worse when the data has not been accessed + for a long time, as with long term archive storage. + Traditional file systems need to run algorithms that check and + repair the data like &man.fsck.8;. These commands take time, + and in severe cases, an administrator has to manually decide + which repair operation must be performed. When + ZFS detects a data block with a checksum + that does not match, it tries to read the data from the mirror + disk. If that disk can provide the correct data, it will not + only give that data to the application requesting it, but also + correct the wrong data on the disk that had the bad checksum. + This happens without any interaction from a system + administrator during normal pool operation. + + The next example demonstrates this self-healing behavior. + A mirrored pool of disks /dev/ada0 and + /dev/ada1 is created. + + &prompt.root; zpool create healer mirror /dev/ada0 /dev/ada1 +&prompt.root; zpool status healer + pool: healer + state: ONLINE + scan: none requested +config: + + NAME STATE READ WRITE CKSUM + healer ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0 ONLINE 0 0 0 + ada1 ONLINE 0 0 0 + +errors: No known data errors +&prompt.root; zpool list +NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT +healer 960M 92.5K 960M 0% 1.00x ONLINE - + + Some important data that to be protected from data errors + using the self-healing feature is copied to the pool. A + checksum of the pool is created for later comparison. + + &prompt.root; cp /some/important/data /healer +&prompt.root; zfs list +NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT +healer 960M 67.7M 892M 7% 1.00x ONLINE - +&prompt.root; sha1 /healer > checksum.txt +&prompt.root; cat checksum.txt +SHA1 (/healer) = 2753eff56d77d9a536ece6694bf0a82740344d1f + + Data corruption is simulated by writing random data to the + beginning of one of the disks in the mirror. To prevent + ZFS from healing the data as soon as it is + detected, the pool is exported before the corruption and + imported again afterwards. + + + This is a dangerous operation that can destroy vital + data. It is shown here for demonstrational purposes only + and should not be attempted during normal operation of a + storage pool. Nor should this intentional corruption + example be run on any disk with a different file system on + it. Do not use any other disk device names other than the + ones that are part of the pool. Make certain that proper + backups of the pool are created before running the + command! + + + &prompt.root; zpool export healer +&prompt.root; dd if=/dev/random of=/dev/ada1 bs=1m count=200 +200+0 records in +200+0 records out +209715200 bytes transferred in 62.992162 secs (3329227 bytes/sec) +&prompt.root; zpool import healer + + The pool status shows that one device has experienced an + error. Note that applications reading data from the pool did + not receive any incorrect data. ZFS + provided data from the ada0 device with + the correct checksums. The device with the wrong checksum can + be found easily as the CKSUM column + contains a nonzero value. + + &prompt.root; zpool status healer + pool: healer + state: ONLINE + status: One or more devices has experienced an unrecoverable error. An + attempt was made to correct the error. Applications are unaffected. + action: Determine if the device needs to be replaced, and clear the errors + using 'zpool clear' or replace the device with 'zpool replace'. + see: http://www.sun.com/msg/ZFS-8000-9P + scan: none requested + config: + + NAME STATE READ WRITE CKSUM + healer ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0 ONLINE 0 0 0 + ada1 ONLINE 0 0 1 + +errors: No known data errors + + The error was detected and handled by using the redundancy + present in the unaffected ada0 mirror + disk. A checksum comparison with the original one will reveal + whether the pool is consistent again. + + &prompt.root; sha1 /healer >> checksum.txt +&prompt.root; cat checksum.txt +SHA1 (/healer) = 2753eff56d77d9a536ece6694bf0a82740344d1f +SHA1 (/healer) = 2753eff56d77d9a536ece6694bf0a82740344d1f + + The two checksums that were generated before and after the + intentional tampering with the pool data still match. This + shows how ZFS is capable of detecting and + correcting any errors automatically when the checksums differ. + Note that this is only possible when there is enough + redundancy present in the pool. A pool consisting of a single + device has no self-healing capabilities. That is also the + reason why checksums are so important in + ZFS and should not be disabled for any + reason. No &man.fsck.8; or similar file system consistency + check program is required to detect and correct this and the + pool was still available during the time there was a problem. + A scrub operation is now required to overwrite the corrupted + data on ada1. + + &prompt.root; zpool scrub healer +&prompt.root; zpool status healer + pool: healer + state: ONLINE +status: One or more devices has experienced an unrecoverable error. An + attempt was made to correct the error. Applications are unaffected. +action: Determine if the device needs to be replaced, and clear the errors + using 'zpool clear' or replace the device with 'zpool replace'. + see: http://www.sun.com/msg/ZFS-8000-9P + scan: scrub in progress since Mon Dec 10 12:23:30 2012 + 10.4M scanned out of 67.0M at 267K/s, 0h3m to go + 9.63M repaired, 15.56% done +config: + + NAME STATE READ WRITE CKSUM + healer ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0 ONLINE 0 0 0 + ada1 ONLINE 0 0 627 (repairing) + +errors: No known data errors + + The scrub operation reads data from + ada0 and rewrites any data with an + incorrect checksum on ada1. This is + indicated by the (repairing) output from + zpool status. After the operation is + complete, the pool status changes to: + + &prompt.root; zpool status healer + pool: healer + state: ONLINE +status: One or more devices has experienced an unrecoverable error. An + attempt was made to correct the error. Applications are unaffected. +action: Determine if the device needs to be replaced, and clear the errors + using 'zpool clear' or replace the device with 'zpool replace'. + see: http://www.sun.com/msg/ZFS-8000-9P + scan: scrub repaired 66.5M in 0h2m with 0 errors on Mon Dec 10 12:26:25 2012 +config: + + NAME STATE READ WRITE CKSUM + healer ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0 ONLINE 0 0 0 + ada1 ONLINE 0 0 2.72K + +errors: No known data errors + + After the scrub operation completes and all the data + has been synchronized from ada0 to + ada1, the error messages can be + cleared from the pool + status by running zpool clear. + + &prompt.root; zpool clear healer +&prompt.root; zpool status healer + pool: healer + state: ONLINE + scan: scrub repaired 66.5M in 0h2m with 0 errors on Mon Dec 10 12:26:25 2012 +config: + + NAME STATE READ WRITE CKSUM + healer ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0 ONLINE 0 0 0 + ada1 ONLINE 0 0 0 + +errors: No known data errors + + The pool is now back to a fully working state and all the + errors have been cleared. + + + + Growing a Pool + + The usable size of a redundant pool is limited by the + capacity of the smallest device in each vdev. The smallest + device can be replaced with a larger device. After completing + a replace or + resilver operation, + the pool can grow to use the capacity of the new device. For + example, consider a mirror of a 1 TB drive and a + 2 drive. The usable space is 1 TB. Then the + 1 TB is replaced with another 2 TB drive, and the + resilvering process duplicates existing data. Because + both of the devices now have 2 TB capacity, the mirror's + available space can be grown to 2 TB. + + Expansion is triggered by using + zpool online -e on each device. After + expansion of all devices, the additional space becomes + available to the pool. + + + + Importing and Exporting Pools + + Pools are exported before moving them + to another system. All datasets are unmounted, and each + device is marked as exported but still locked so it cannot be + used by other disk subsystems. This allows pools to be + imported on other machines, other + operating systems that support ZFS, and + even different hardware architectures (with some caveats, see + &man.zpool.8;). When a dataset has open files, + zpool export -f can be used to force the + export of a pool. Use this with caution. The datasets are + forcibly unmounted, potentially resulting in unexpected + behavior by the applications which had open files on those + datasets. + + Export a pool that is not in use: + + &prompt.root; zpool export mypool + + Importing a pool automatically mounts the datasets. This + may not be the desired behavior, and can be prevented with + zpool import -N. + zpool import -o sets temporary properties + for this import only. + zpool import altroot= allows importing a + pool with a base mount point instead of the root of the file + system. If the pool was last used on a different system and + was not properly exported, an import might have to be forced + with zpool import -f. + zpool import -a imports all pools that do + not appear to be in use by another system. + + List all available pools for import: + + &prompt.root; zpool import + pool: mypool + id: 9930174748043525076 + state: ONLINE + action: The pool can be imported using its name or numeric identifier. + config: + + mypool ONLINE + ada2p3 ONLINE + + Import the pool with an alternative root directory: + + &prompt.root; zpool import -o altroot=/mnt mypool +&prompt.root; zfs list +zfs list +NAME USED AVAIL REFER MOUNTPOINT +mypool 110K 47.0G 31K /mnt/mypool + + + + Upgrading a Storage Pool + + After upgrading &os;, or if a pool has been imported from + a system using an older version of ZFS, the + pool can be manually upgraded to the latest version of + ZFS to support newer features. Consider + whether the pool may ever need to be imported on an older + system before upgrading. Upgrading is a one-way process. + Older pools can be upgraded, but pools with newer features + cannot be downgraded. + + Upgrade a v28 pool to support + Feature Flags: + + &prompt.root; zpool status + pool: mypool + state: ONLINE +status: The pool is formatted using a legacy on-disk format. The pool can + still be used, but some features are unavailable. +action: Upgrade the pool using 'zpool upgrade'. Once this is done, the + pool will no longer be accessible on software that does not support feat + flags. + scan: none requested +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0 ONLINE 0 0 0 + ada1 ONLINE 0 0 0 + +errors: No known data errors +&prompt.root; zpool upgrade +This system supports ZFS pool feature flags. + +The following pools are formatted with legacy version numbers and can +be upgraded to use feature flags. After being upgraded, these pools +will no longer be accessible by software that does not support feature +flags. + +VER POOL +--- ------------ +28 mypool + +Use 'zpool upgrade -v' for a list of available legacy versions. +Every feature flags pool has all supported features enabled. +&prompt.root; zpool upgrade mypool +This system supports ZFS pool feature flags. + +Successfully upgraded 'mypool' from version 28 to feature flags. +Enabled the following features on 'mypool': + async_destroy + empty_bpobj + lz4_compress + multi_vdev_crash_dump + + The newer features of ZFS will not be + available until zpool upgrade has + completed. zpool upgrade -v can be used to + see what new features will be provided by upgrading, as well + as which features are already supported. + + Upgrade a pool to support additional feature flags: + + &prompt.root; zpool status + pool: mypool + state: ONLINE +status: Some supported features are not enabled on the pool. The pool can + still be used, but some features are unavailable. +action: Enable all features using 'zpool upgrade'. Once this is done, + the pool may no longer be accessible by software that does not support + the features. See zpool-features(7) for details. + scan: none requested +config: + + NAME STATE READ WRITE CKSUM + mypool ONLINE 0 0 0 + mirror-0 ONLINE 0 0 0 + ada0 ONLINE 0 0 0 + ada1 ONLINE 0 0 0 + +errors: No known data errors +&prompt.root; zpool upgrade +This system supports ZFS pool feature flags. + +All pools are formatted using feature flags. + + +Some supported features are not enabled on the following pools. Once a +feature is enabled the pool may become incompatible with software +that does not support the feature. See zpool-features(7) for details. + +POOL FEATURE +--------------- +zstore + multi_vdev_crash_dump + spacemap_histogram + enabled_txg + hole_birth + extensible_dataset + bookmarks + filesystem_limits +&prompt.root; zpool upgrade mypool +This system supports ZFS pool feature flags. + +Enabled the following features on 'mypool': + spacemap_histogram + enabled_txg + hole_birth + extensible_dataset + bookmarks + filesystem_limits + + + The boot code on systems that boot from a pool must be + updated to support the new pool version. Use + gpart bootcode on the partition that + contains the boot code. See &man.gpart.8; for more + information. + + + + + Displaying Recorded Pool History + + Commands that modify the pool are recorded. Recorded + actions include the creation of datasets, changing properties, + or replacement of a disk. This history is useful for + reviewing how a pool was created and which user performed a + specific action and when. History is not kept in a log file, + but is part of the pool itself. The command to review this + history is aptly named + zpool history: + + &prompt.root; zpool history +History for 'tank': +2013-02-26.23:02:35 zpool create tank mirror /dev/ada0 /dev/ada1 +2013-02-27.18:50:58 zfs set atime=off tank +2013-02-27.18:51:09 zfs set checksum=fletcher4 tank +2013-02-27.18:51:18 zfs create tank/backup + + The output shows zpool and + zfs commands that were executed on the pool + along with a timestamp. Only commands that alter the pool in + some way are recorded. Commands like + zfs list are not included. When no pool + name is specified, the history of all pools is + displayed. + + zpool history can show even more + information when the options or + are provided. + displays user-initiated events as well as internally logged + ZFS events. + + &prompt.root; zpool history -i +History for 'tank': +2013-02-26.23:02:35 [internal pool create txg:5] pool spa 28; zfs spa 28; zpl 5;uts 9.1-RELEASE 901000 amd64 +2013-02-27.18:50:53 [internal property set txg:50] atime=0 dataset = 21 +2013-02-27.18:50:58 zfs set atime=off tank +2013-02-27.18:51:04 [internal property set txg:53] checksum=7 dataset = 21 +2013-02-27.18:51:09 zfs set checksum=fletcher4 tank +2013-02-27.18:51:13 [internal create txg:55] dataset = 39 +2013-02-27.18:51:18 zfs create tank/backup + + More details can be shown by adding . + History records are shown in a long format, including + information like the name of the user who issued the command + and the hostname on which the change was made. + + &prompt.root; zpool history -l +History for 'tank': +2013-02-26.23:02:35 zpool create tank mirror /dev/ada0 /dev/ada1 [user 0 (root) on :global] +2013-02-27.18:50:58 zfs set atime=off tank [user 0 (root) on myzfsbox:global] +2013-02-27.18:51:09 zfs set checksum=fletcher4 tank [user 0 (root) on myzfsbox:global] +2013-02-27.18:51:18 zfs create tank/backup [user 0 (root) on myzfsbox:global] + + The output shows that the + root user created + the mirrored pool with disks + /dev/ada0 and + /dev/ada1. The hostname + myzfsbox is also + shown in the commands after the pool's creation. The hostname + display becomes important when the pool is exported from one + system and imported on another. The commands that are issued + on the other system can clearly be distinguished by the + hostname that is recorded for each command. + + Both options to zpool history can be + combined to give the most detailed information possible for + any given pool. Pool history provides valuable information + when tracking down the actions that were performed or when + more detailed output is needed for debugging. + + + + Performance Monitoring + + A built-in monitoring system can display pool + I/O statistics in real time. It shows the + amount of free and used space on the pool, how many read and + write operations are being performed per second, and how much + I/O bandwidth is currently being utilized. + By default, all pools in the system are monitored and + displayed. A pool name can be provided to limit monitoring to + just that pool. A basic example: + + &prompt.root; zpool iostat + capacity operations bandwidth +pool alloc free read write read write +---------- ----- ----- ----- ----- ----- ----- +data 288G 1.53T 2 11 11.3K 57.1K + + To continuously monitor I/O activity, a + number can be specified as the last parameter, indicating a + interval in seconds to wait between updates. The next + statistic line is printed after each interval. Press + + Ctrl + C + to stop this continuous monitoring. + Alternatively, give a second number on the command line after + the interval to specify the total number of statistics to + display. + + Even more detailed I/O statistics can + be displayed with . Each device in the + pool is shown with a statistics line. This is useful in + seeing how many read and write operations are being performed + on each device, and can help determine if any individual + device is slowing down the pool. This example shows a + mirrored pool with two devices: + + &prompt.root; zpool iostat -v + capacity operations bandwidth +pool alloc free read write read write +----------------------- ----- ----- ----- ----- ----- ----- +data 288G 1.53T 2 12 9.23K 61.5K + mirror 288G 1.53T 2 12 9.23K 61.5K + ada1 - - 0 4 5.61K 61.7K + ada2 - - 1 4 5.04K 61.7K +----------------------- ----- ----- ----- ----- ----- ----- + + + + Splitting a Storage Pool + + A pool consisting of one or more mirror vdevs can be split + into two pools. Unless otherwise specified, the last member + of each mirror is detached and used to create a new pool + containing the same data. The operation should first be + attempted with . The details of the + proposed operation are displayed without it actually being + performed. This helps confirm that the operation will do what + the user intends. + + + + + <command>zfs</command> Administration + + The zfs utility is responsible for + creating, destroying, and managing all ZFS + datasets that exist within a pool. The pool is managed using + zpool. + + + Creating and Destroying Datasets + + Unlike traditional disks and volume managers, space in + ZFS is not + preallocated. With traditional file systems, after all of the + space is partitioned and assigned, there is no way to add an + additional file system without adding a new disk. With + ZFS, new file systems can be created at any + time. Each dataset + has properties including features like compression, + deduplication, caching, and quotas, as well as other useful + properties like readonly, case sensitivity, network file + sharing, and a mount point. Datasets can be nested inside + each other, and child datasets will inherit properties from + their parents. Each dataset can be administered, + delegated, + replicated, + snapshotted, + jailed, and destroyed as a + unit. There are many advantages to creating a separate + dataset for each different type or set of files. The only + drawbacks to having an extremely large number of datasets is + that some commands like zfs list will be + slower, and the mounting of hundreds or even thousands of + datasets can slow the &os; boot process. + + Create a new dataset and enable LZ4 + compression on it: + + &prompt.root; zfs list +NAME USED AVAIL REFER MOUNTPOINT +mypool 781M 93.2G 144K none +mypool/ROOT 777M 93.2G 144K none +mypool/ROOT/default 777M 93.2G 777M / +mypool/tmp 176K 93.2G 176K /tmp +mypool/usr 616K 93.2G 144K /usr +mypool/usr/home 184K 93.2G 184K /usr/home +mypool/usr/ports 144K 93.2G 144K /usr/ports +mypool/usr/src 144K 93.2G 144K /usr/src +mypool/var 1.20M 93.2G 608K /var +mypool/var/crash 148K 93.2G 148K /var/crash +mypool/var/log 178K 93.2G 178K /var/log +mypool/var/mail 144K 93.2G 144K /var/mail +mypool/var/tmp 152K 93.2G 152K /var/tmp +&prompt.root; zfs create -o compress=lz4 mypool/usr/mydataset +&prompt.root; zfs list +NAME USED AVAIL REFER MOUNTPOINT +mypool 781M 93.2G 144K none +mypool/ROOT 777M 93.2G 144K none +mypool/ROOT/default 777M 93.2G 777M / +mypool/tmp 176K 93.2G 176K /tmp +mypool/usr 704K 93.2G 144K /usr +mypool/usr/home 184K 93.2G 184K /usr/home +mypool/usr/mydataset 87.5K 93.2G 87.5K /usr/mydataset +mypool/usr/ports 144K 93.2G 144K /usr/ports +mypool/usr/src 144K 93.2G 144K /usr/src +mypool/var 1.20M 93.2G 610K /var +mypool/var/crash 148K 93.2G 148K /var/crash +mypool/var/log 178K 93.2G 178K /var/log +mypool/var/mail 144K 93.2G 144K /var/mail +mypool/var/tmp 152K 93.2G 152K /var/tmp + + Destroying a dataset is much quicker than deleting all + of the files that reside on the dataset, as it does not + involve scanning all of the files and updating all of the + corresponding metadata. + + Destroy the previously-created dataset: + + &prompt.root; zfs list +NAME USED AVAIL REFER MOUNTPOINT +mypool 880M 93.1G 144K none +mypool/ROOT 777M 93.1G 144K none +mypool/ROOT/default 777M 93.1G 777M / +mypool/tmp 176K 93.1G 176K /tmp +mypool/usr 101M 93.1G 144K /usr +mypool/usr/home 184K 93.1G 184K /usr/home +mypool/usr/mydataset 100M 93.1G 100M /usr/mydataset +mypool/usr/ports 144K 93.1G 144K /usr/ports +mypool/usr/src 144K 93.1G 144K /usr/src +mypool/var 1.20M 93.1G 610K /var +mypool/var/crash 148K 93.1G 148K /var/crash +mypool/var/log 178K 93.1G 178K /var/log +mypool/var/mail 144K 93.1G 144K /var/mail +mypool/var/tmp 152K 93.1G 152K /var/tmp +&prompt.root; zfs destroy mypool/usr/mydataset +&prompt.root; zfs list +NAME USED AVAIL REFER MOUNTPOINT +mypool 781M 93.2G 144K none +mypool/ROOT 777M 93.2G 144K none +mypool/ROOT/default 777M 93.2G 777M / +mypool/tmp 176K 93.2G 176K /tmp +mypool/usr 616K 93.2G 144K /usr +mypool/usr/home 184K 93.2G 184K /usr/home +mypool/usr/ports 144K 93.2G 144K /usr/ports +mypool/usr/src 144K 93.2G 144K /usr/src +mypool/var 1.21M 93.2G 612K /var +mypool/var/crash 148K 93.2G 148K /var/crash +mypool/var/log 178K 93.2G 178K /var/log +mypool/var/mail 144K 93.2G 144K /var/mail +mypool/var/tmp 152K 93.2G 152K /var/tmp + + In modern versions of ZFS, + zfs destroy is asynchronous, and the free + space might take several minutes to appear in the pool. Use + zpool get freeing + poolname to see the + freeing property, indicating how many + datasets are having their blocks freed in the background. + If there are child datasets, like + snapshots or other + datasets, then the parent cannot be destroyed. To destroy a + dataset and all of its children, use to + recursively destroy the dataset and all of its children. + Use to list datasets + and snapshots that would be destroyed by this operation, but + do not actually destroy anything. Space that would be + reclaimed by destruction of snapshots is also shown. + + + + Creating and Destroying Volumes + + A volume is a special type of dataset. Rather than being + mounted as a file system, it is exposed as a block device + under + /dev/zvol/poolname/dataset. + This allows the volume to be used for other file systems, to + back the disks of a virtual machine, or to be exported using + protocols like iSCSI or + HAST. + + A volume can be formatted with any file system, or used + without a file system to store raw data. To the user, a + volume appears to be a regular disk. Putting ordinary file + systems on these zvols provides features + that ordinary disks or file systems do not normally have. For + example, using the compression property on a 250 MB + volume allows creation of a compressed FAT + file system. + + &prompt.root; zfs create -V 250m -o compression=on tank/fat32 +&prompt.root; zfs list tank +NAME USED AVAIL REFER MOUNTPOINT +tank 258M 670M 31K /tank +&prompt.root; newfs_msdos -F32 /dev/zvol/tank/fat32 +&prompt.root; mount -t msdosfs /dev/zvol/tank/fat32 /mnt +&prompt.root; df -h /mnt | grep fat32 +Filesystem Size Used Avail Capacity Mounted on +/dev/zvol/tank/fat32 249M 24k 249M 0% /mnt +&prompt.root; mount | grep fat32 +/dev/zvol/tank/fat32 on /mnt (msdosfs, local) + + Destroying a volume is much the same as destroying a + regular file system dataset. The operation is nearly + instantaneous, but it may take several minutes for the free + space to be reclaimed in the background. + + + + Renaming a Dataset + + The name of a dataset can be changed with + zfs rename. The parent of a dataset can + also be changed with this command. Renaming a dataset to be + under a different parent dataset will change the value of + those properties that are inherited from the parent dataset. + When a dataset is renamed, it is unmounted and then remounted + in the new location (which is inherited from the new parent + dataset). This behavior can be prevented with + . + + Rename a dataset and move it to be under a different + parent dataset: + + &prompt.root; zfs list +NAME USED AVAIL REFER MOUNTPOINT +mypool 780M 93.2G 144K none +mypool/ROOT 777M 93.2G 144K none +mypool/ROOT/default 777M 93.2G 777M / +mypool/tmp 176K 93.2G 176K /tmp +mypool/usr 704K 93.2G 144K /usr +mypool/usr/home 184K 93.2G 184K /usr/home +mypool/usr/mydataset 87.5K 93.2G 87.5K /usr/mydataset +mypool/usr/ports 144K 93.2G 144K /usr/ports +mypool/usr/src 144K 93.2G 144K /usr/src +mypool/var 1.21M 93.2G 614K /var +mypool/var/crash 148K 93.2G 148K /var/crash +mypool/var/log 178K 93.2G 178K /var/log +mypool/var/mail 144K 93.2G 144K /var/mail +mypool/var/tmp 152K 93.2G 152K /var/tmp +&prompt.root; zfs rename mypool/usr/mydataset mypool/var/newname +&prompt.root; zfs list +NAME USED AVAIL REFER MOUNTPOINT +mypool 780M 93.2G 144K none +mypool/ROOT 777M 93.2G 144K none +mypool/ROOT/default 777M 93.2G 777M / +mypool/tmp 176K 93.2G 176K /tmp +mypool/usr 616K 93.2G 144K /usr +mypool/usr/home 184K 93.2G 184K /usr/home +mypool/usr/ports 144K 93.2G 144K /usr/ports +mypool/usr/src 144K 93.2G 144K /usr/src +mypool/var 1.29M 93.2G 614K /var +mypool/var/crash 148K 93.2G 148K /var/crash +mypool/var/log 178K 93.2G 178K /var/log +mypool/var/mail 144K 93.2G 144K /var/mail +mypool/var/newname 87.5K 93.2G 87.5K /var/newname +mypool/var/tmp 152K 93.2G 152K /var/tmp + + Snapshots can also be renamed like this. Due to the + nature of snapshots, they cannot be renamed into a different + parent dataset. To rename a recursive snapshot, specify + , and all snapshots with the same name in + child datasets with also be renamed. + + &prompt.root; zfs list -t snapshot +NAME USED AVAIL REFER MOUNTPOINT +mypool/var/newname@first_snapshot 0 - 87.5K - +&prompt.root; zfs rename mypool/var/newname@first_snapshot new_snapshot_name +&prompt.root; zfs list -t snapshot +NAME USED AVAIL REFER MOUNTPOINT +mypool/var/newname@new_snapshot_name 0 - 87.5K - + + + + Setting Dataset Properties + + Each ZFS dataset has a number of + properties that control its behavior. Most properties are + automatically inherited from the parent dataset, but can be + overridden locally. Set a property on a dataset with + zfs set + property=value + dataset. Most + properties have a limited set of valid values, + zfs get will display each possible property + and valid values. Most properties can be reverted to their + inherited values using zfs inherit. + + User-defined properties can also be set. They become part + of the dataset configuration and can be used to provide + additional information about the dataset or its contents. To + distinguish these custom properties from the ones supplied as + part of ZFS, a colon (:) + is used to create a custom namespace for the property. + + &prompt.root; zfs set custom:costcenter=1234 tank +&prompt.root; zfs get custom:costcenter tank +NAME PROPERTY VALUE SOURCE +tank custom:costcenter 1234 local + + To remove a custom property, use + zfs inherit with . If + the custom property is not defined in any of the parent + datasets, it will be removed completely (although the changes + are still recorded in the pool's history). + + &prompt.root; zfs inherit -r custom:costcenter tank +&prompt.root; zfs get custom:costcenter tank +NAME PROPERTY VALUE SOURCE +tank custom:costcenter - - +&prompt.root; zfs get all tank | grep custom:costcenter +&prompt.root; + + + + Managing Snapshots + + Snapshots are one + of the most powerful features of ZFS. A + snapshot provides a read-only, point-in-time copy of the + dataset. With Copy-On-Write (COW), + snapshots can be created quickly by preserving the older + version of the data on disk. If no snapshots exist, space is + reclaimed for future use when data is rewritten or deleted. + Snapshots preserve disk space by recording only the + differences between the current dataset and a previous + version. Snapshots are allowed only on whole datasets, not on + individual files or directories. When a snapshot is created + from a dataset, everything contained in it is duplicated. + This includes the file system properties, files, directories, + permissions, and so on. Snapshots use no additional space + when they are first created, only consuming space as the + blocks they reference are changed. Recursive snapshots taken + with create a snapshot with the same name + on the dataset and all of its children, providing a consistent + moment-in-time snapshot of all of the file systems. This can + be important when an application has files on multiple + datasets that are related or dependent upon each other. + Without snapshots, a backup would have copies of the files + from different points in time. + + Snapshots in ZFSprovide a variety of + features that even other file systems with snapshot + functionality lack. A typical example of snapshot use is to + have a quick way of backing up the current state of the file + system when a risky action like a software installation or a + system upgrade is performed. If the action fails, the + snapshot can be rolled back and the system has the same state + as when the snapshot was created. If the upgrade was + successful, the snapshot can be deleted to free up space. + Without snapshots, a failed upgrade often requires a restore + from backup, which is tedious, time consuming, and may require + downtime during which the system cannot be used. Snapshots + can be rolled back quickly, even while the system is running + in normal operation, with little or no downtime. The time + savings are enormous with multi-terabyte storage systems and + the time required to copy the data from backup. Snapshots are + not a replacement for a complete backup of a pool, but can be + used as a quick and easy way to store a copy of the dataset at + a specific point in time. + + + Creating Snapshots + + Snapshots are created with zfs snapshot + dataset@snapshotname. + Adding creates a snapshot recursively, + with the same name on all child datasets. + + Create a recursive snapshot of the entire pool: + + &prompt.root; zfs list -t all +NAME USED AVAIL REFER MOUNTPOINT +mypool 780M 93.2G 144K none +mypool/ROOT 777M 93.2G 144K none +mypool/ROOT/default 777M 93.2G 777M / +mypool/tmp 176K 93.2G 176K /tmp +mypool/usr 616K 93.2G 144K /usr +mypool/usr/home 184K 93.2G 184K /usr/home +mypool/usr/ports 144K 93.2G 144K /usr/ports +mypool/usr/src 144K 93.2G 144K /usr/src +mypool/var 1.29M 93.2G 616K /var +mypool/var/crash 148K 93.2G 148K /var/crash +mypool/var/log 178K 93.2G 178K /var/log +mypool/var/mail 144K 93.2G 144K /var/mail +mypool/var/newname 87.5K 93.2G 87.5K /var/newname +mypool/var/newname@new_snapshot_name 0 - 87.5K - +mypool/var/tmp 152K 93.2G 152K /var/tmp +&prompt.root; zfs snapshot -r mypool@my_recursive_snapshot +&prompt.root; zfs list -t snapshot +NAME USED AVAIL REFER MOUNTPOINT +mypool@my_recursive_snapshot 0 - 144K - +mypool/ROOT@my_recursive_snapshot 0 - 144K - +mypool/ROOT/default@my_recursive_snapshot 0 - 777M - +mypool/tmp@my_recursive_snapshot 0 - 176K - +mypool/usr@my_recursive_snapshot 0 - 144K - +mypool/usr/home@my_recursive_snapshot 0 - 184K - +mypool/usr/ports@my_recursive_snapshot 0 - 144K - +mypool/usr/src@my_recursive_snapshot 0 - 144K - +mypool/var@my_recursive_snapshot 0 - 616K - +mypool/var/crash@my_recursive_snapshot 0 - 148K - +mypool/var/log@my_recursive_snapshot 0 - 178K - +mypool/var/mail@my_recursive_snapshot 0 - 144K - +mypool/var/newname@new_snapshot_name 0 - 87.5K - +mypool/var/newname@my_recursive_snapshot 0 - 87.5K - +mypool/var/tmp@my_recursive_snapshot 0 - 152K - + + Snapshots are not shown by a normal + zfs list operation. To list snapshots, + is appended to + zfs list. + displays both file systems and snapshots. + + Snapshots are not mounted directly, so path is shown in + the MOUNTPOINT column. There is no + mention of available disk space in the + AVAIL column, as snapshots cannot be + written to after they are created. Compare the snapshot + to the original dataset from which it was created: + + &prompt.root; zfs list -rt all mypool/usr/home +NAME USED AVAIL REFER MOUNTPOINT +mypool/usr/home 184K 93.2G 184K /usr/home +mypool/usr/home@my_recursive_snapshot 0 - 184K - + + Displaying both the dataset and the snapshot together + reveals how snapshots work in + COW fashion. They save + only the changes (delta) that were made + and not the complete file system contents all over again. + This means that snapshots take little space when few changes + are made. Space usage can be made even more apparent by + copying a file to the dataset, then making a second + snapshot: + + &prompt.root; cp /etc/passwd /var/tmp +&prompt.root; zfs snapshot mypool/var/tmp@after_cp +&prompt.root; zfs list -rt all mypool/var/tmp +NAME USED AVAIL REFER MOUNTPOINT +mypool/var/tmp 206K 93.2G 118K /var/tmp +mypool/var/tmp@my_recursive_snapshot 88K - 152K - +mypool/var/tmp@after_cp 0 - 118K - + + The second snapshot contains only the changes to the + dataset after the copy operation. This yields enormous + space savings. Notice that the size of the snapshot + mypool/var/tmp@my_recursive_snapshot + also changed in the USED + column to indicate the changes between itself and the + snapshot taken afterwards. + + + + Comparing Snapshots + + ZFS provides a built-in command to compare the + differences in content between two snapshots. This is + helpful when many snapshots were taken over time and the + user wants to see how the file system has changed over time. + For example, zfs diff lets a user find + the latest snapshot that still contains a file that was + accidentally deleted. Doing this for the two snapshots that + were created in the previous section yields this + output: + + &prompt.root; zfs list -rt all mypool/var/tmp +NAME USED AVAIL REFER MOUNTPOINT +mypool/var/tmp 206K 93.2G 118K /var/tmp +mypool/var/tmp@my_recursive_snapshot 88K - 152K - +mypool/var/tmp@after_cp 0 - 118K - +&prompt.root; zfs diff mypool/var/tmp@my_recursive_snapshot +M /var/tmp/ ++ /var/tmp/passwd + + The command lists the changes between the specified + snapshot (in this case + mypool/var/tmp@my_recursive_snapshot) + and the live file system. The first column shows the + type of change: + + + + + + + + The path or file was added. + + + + - + The path or file was deleted. + + + + M + The path or file was modified. + + + + R + The path or file was renamed. + + + + + + Comparing the output with the table, it becomes clear + that passwd + was added after the snapshot + mypool/var/tmp@my_recursive_snapshot + was created. This also resulted in a modification to the + parent directory mounted at + /var/tmp. + + Comparing two snapshots is helpful when using the + ZFS replication feature to transfer a + dataset to a different host for backup purposes. + + Compare two snapshots by providing the full dataset name + and snapshot name of both datasets: + + &prompt.root; cp /var/tmp/passwd /var/tmp/passwd.copy +&prompt.root; zfs snapshot mypool/var/tmp@diff_snapshot +&prompt.root; zfs diff mypool/var/tmp@my_recursive_snapshot mypool/var/tmp@diff_snapshot +M /var/tmp/ ++ /var/tmp/passwd ++ /var/tmp/passwd.copy +&prompt.root; zfs diff mypool/var/tmp@my_recursive_snapshot mypool/var/tmp@after_cp +M /var/tmp/ ++ /var/tmp/passwd + + A backup administrator can compare two snapshots + received from the sending host and determine the actual + changes in the dataset. See the + Replication section for + more information. + + + + Snapshot Rollback + + When at least one snapshot is available, it can be + rolled back to at any time. Most of the time this is the + case when the current state of the dataset is no longer + required and an older version is preferred. Scenarios such + as local development tests have gone wrong, botched system + updates hampering the system's overall functionality, or the + requirement to restore accidentally deleted files or + directories are all too common occurrences. Luckily, + rolling back a snapshot is just as easy as typing + zfs rollback + snapshotname. + Depending on how many changes are involved, the operation + will finish in a certain amount of time. During that time, + the dataset always remains in a consistent state, much like + a database that conforms to ACID principles is performing a + rollback. This is happening while the dataset is live and + accessible without requiring a downtime. Once the snapshot + has been rolled back, the dataset has the same state as it + had when the snapshot was originally taken. All other data + in that dataset that was not part of the snapshot is + discarded. Taking a snapshot of the current state of the + dataset before rolling back to a previous one is a good idea + when some data is required later. This way, the user can + roll back and forth between snapshots without losing data + that is still valuable. + + In the first example, a snapshot is rolled back because + of a careless rm operation that removes + too much data than was intended. + + &prompt.root; zfs list -rt all mypool/var/tmp +NAME USED AVAIL REFER MOUNTPOINT +mypool/var/tmp 262K 93.2G 120K /var/tmp +mypool/var/tmp@my_recursive_snapshot 88K - 152K - +mypool/var/tmp@after_cp 53.5K - 118K - +mypool/var/tmp@diff_snapshot 0 - 120K - +&prompt.user; ls /var/tmp +passwd passwd.copy +&prompt.user; rm /var/tmp/passwd* +&prompt.user; ls /var/tmp +vi.recover +&prompt.user; + + At this point, the user realized that too many files + were deleted and wants them back. ZFS + provides an easy way to get them back using rollbacks, but + only when snapshots of important data are performed on a + regular basis. To get the files back and start over from + the last snapshot, issue the command: + + &prompt.root; zfs rollback mypool/var/tmp@diff_snapshot +&prompt.user; ls /var/tmp +passwd passwd.copy vi.recover + + The rollback operation restored the dataset to the state + of the last snapshot. It is also possible to roll back to a + snapshot that was taken much earlier and has other snapshots + that were created after it. When trying to do this, + ZFS will issue this warning: + + &prompt.root; zfs list -rt snapshot mypool/var/tmp +AME USED AVAIL REFER MOUNTPOINT +mypool/var/tmp@my_recursive_snapshot 88K - 152K - +mypool/var/tmp@after_cp 53.5K - 118K - +mypool/var/tmp@diff_snapshot 0 - 120K - +&prompt.root; zfs rollback mypool/var/tmp@my_recursive_snapshot +cannot rollback to 'mypool/var/tmp@my_recursive_snapshot': more recent snapshots exist +use '-r' to force deletion of the following snapshots: +mypool/var/tmp@after_cp +mypool/var/tmp@diff_snapshot + + This warning means that snapshots exist between the + current state of the dataset and the snapshot to which the + user wants to roll back. To complete the rollback, these + snapshots must be deleted. ZFS cannot + track all the changes between different states of the + dataset, because snapshots are read-only. + ZFS will not delete the affected + snapshots unless the user specifies to + indicate that this is the desired action. If that is the + intention, and the consequences of losing all intermediate + snapshots is understood, the command can be issued: + + &prompt.root; zfs rollback -r mypool/var/tmp@my_recursive_snapshot +&prompt.root; zfs list -rt snapshot mypool/var/tmp +NAME USED AVAIL REFER MOUNTPOINT +mypool/var/tmp@my_recursive_snapshot 8K - 152K - +&prompt.user; ls /var/tmp +vi.recover + + The output from zfs list -t snapshot + confirms that the intermediate snapshots + were removed as a result of + zfs rollback -r. + + + + Restoring Individual Files from Snapshots + + Snapshots are mounted in a hidden directory under the + parent dataset: + .zfs/snapshots/snapshotname. + By default, these directories will not be displayed even + when a standard ls -a is issued. + Although the directory is not displayed, it is there + nevertheless and can be accessed like any normal directory. + The property named snapdir controls + whether these hidden directories show up in a directory + listing. Setting the property to visible + allows them to appear in the output of ls + and other commands that deal with directory contents. + + &prompt.root; zfs get snapdir mypool/var/tmp +NAME PROPERTY VALUE SOURCE +mypool/var/tmp snapdir hidden default +&prompt.user; ls -a /var/tmp +. .. passwd vi.recover +&prompt.root; zfs set snapdir=visible mypool/var/tmp +&prompt.user; ls -a /var/tmp +. .. .zfs passwd vi.recover + + Individual files can easily be restored to a previous + state by copying them from the snapshot back to the parent + dataset. The directory structure below + .zfs/snapshot has a directory named + exactly like the snapshots taken earlier to make it easier + to identify them. In the next example, it is assumed that a + file is to be restored from the hidden + .zfs directory by copying it from the + snapshot that contained the latest version of the + file: + + &prompt.root; rm /var/tmp/passwd +&prompt.user; ls -a /var/tmp +. .. .zfs vi.recover +&prompt.root; ls /var/tmp/.zfs/snapshot +after_cp my_recursive_snapshot +&prompt.root; ls /var/tmp/.zfs/snapshot/after_cp +passwd vi.recover +&prompt.root; cp /var/tmp/.zfs/snapshot/after_cp/passwd /var/tmp + + When ls .zfs/snapshot was issued, the + snapdir property might have been set to + hidden, but it would still be possible to list the contents + of that directory. It is up to the administrator to decide + whether these directories will be displayed. It is possible + to display these for certain datasets and prevent it for + others. Copying files or directories from this hidden + .zfs/snapshot is simple enough. Trying + it the other way around results in this error: + + &prompt.root; cp /etc/rc.conf /var/tmp/.zfs/snapshot/after_cp/ +cp: /var/tmp/.zfs/snapshot/after_cp/rc.conf: Read-only file system + + The error reminds the user that snapshots are read-only + and can not be changed after creation. No files can be + copied into or removed from snapshot directories because + that would change the state of the dataset they + represent. + + Snapshots consume space based on how much the parent + file system has changed since the time of the snapshot. The + written property of a snapshot tracks how + much space is being used by the snapshot. + + Snapshots are destroyed and the space reclaimed with + zfs destroy + dataset@snapshot. + Adding recursively removes all snapshots + with the same name under the parent dataset. Adding + to the command displays a list of the + snapshots that would be deleted and an estimate of how much + space would be reclaimed without performing the actual + destroy operation. + + + + + Managing Clones + + A clone is a copy of a snapshot that is treated more like + a regular dataset. Unlike a snapshot, a clone is not read + only, is mounted, and can have its own properties. Once a + clone has been created using zfs clone, the + snapshot it was created from cannot be destroyed. The + child/parent relationship between the clone and the snapshot + can be reversed using zfs promote. After a + clone has been promoted, the snapshot becomes a child of the + clone, rather than of the original parent dataset. This will + change how the space is accounted, but not actually change the + amount of space consumed. The clone can be mounted at any + point within the ZFS file system hierarchy, + not just below the original location of the snapshot. + + To demonstrate the clone feature, this example dataset is + used: + + &prompt.root; zfs list -rt all camino/home/joe +NAME USED AVAIL REFER MOUNTPOINT +camino/home/joe 108K 1.3G 87K /usr/home/joe +camino/home/joe@plans 21K - 85.5K - +camino/home/joe@backup 0K - 87K - + + A typical use for clones is to experiment with a specific + dataset while keeping the snapshot around to fall back to in + case something goes wrong. Since snapshots can not be + changed, a read/write clone of a snapshot is created. After + the desired result is achieved in the clone, the clone can be + promoted to a dataset and the old file system removed. This + is not strictly necessary, as the clone and dataset can + coexist without problems. + + &prompt.root; zfs clone camino/home/joe@backup camino/home/joenew +&prompt.root; ls /usr/home/joe* +/usr/home/joe: +backup.txz plans.txt + +/usr/home/joenew: +backup.txz plans.txt +&prompt.root; df -h /usr/home +Filesystem Size Used Avail Capacity Mounted on +usr/home/joe 1.3G 31k 1.3G 0% /usr/home/joe +usr/home/joenew 1.3G 31k 1.3G 0% /usr/home/joenew + + After a clone is created it is an exact copy of the state + the dataset was in when the snapshot was taken. The clone can + now be changed independently from its originating dataset. + The only connection between the two is the snapshot. + ZFS records this connection in the property + origin. Once the dependency between the + snapshot and the clone has been removed by promoting the clone + using zfs promote, the + origin of the clone is removed as it is now + an independent dataset. This example demonstrates it: + + &prompt.root; zfs get origin camino/home/joenew +NAME PROPERTY VALUE SOURCE +camino/home/joenew origin camino/home/joe@backup - +&prompt.root; zfs promote camino/home/joenew +&prompt.root; zfs get origin camino/home/joenew +NAME PROPERTY VALUE SOURCE +camino/home/joenew origin - - + + After making some changes like copying + loader.conf to the promoted clone, for + example, the old directory becomes obsolete in this case. + Instead, the promoted clone can replace it. This can be + achieved by two consecutive commands: zfs + destroy on the old dataset and zfs + rename on the clone to name it like the old + dataset (it could also get an entirely different name). + + &prompt.root; cp /boot/defaults/loader.conf /usr/home/joenew +&prompt.root; zfs destroy -f camino/home/joe +&prompt.root; zfs rename camino/home/joenew camino/home/joe +&prompt.root; ls /usr/home/joe +backup.txz loader.conf plans.txt +&prompt.root; df -h /usr/home +Filesystem Size Used Avail Capacity Mounted on +usr/home/joe 1.3G 128k 1.3G 0% /usr/home/joe + + The cloned snapshot is now handled like an ordinary + dataset. It contains all the data from the original snapshot + plus the files that were added to it like + loader.conf. Clones can be used in + different scenarios to provide useful features to ZFS users. + For example, jails could be provided as snapshots containing + different sets of installed applications. Users can clone + these snapshots and add their own applications as they see + fit. Once they are satisfied with the changes, the clones can + be promoted to full datasets and provided to end users to work + with like they would with a real dataset. This saves time and + administrative overhead when providing these jails. + + + + Replication + + Keeping data on a single pool in one location exposes + it to risks like theft and natural or human disasters. Making + regular backups of the entire pool is vital. + ZFS provides a built-in serialization + feature that can send a stream representation of the data to + standard output. Using this technique, it is possible to not + only store the data on another pool connected to the local + system, but also to send it over a network to another system. + Snapshots are the basis for this replication (see the section + on ZFS + snapshots). The commands used for replicating data + are zfs send and + zfs receive. + + These examples demonstrate ZFS + replication with these two pools: + + &prompt.root; zpool list +NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT +backup 960M 77K 896M 0% 1.00x ONLINE - +mypool 984M 43.7M 940M 4% 1.00x ONLINE - + + The pool named mypool is the + primary pool where data is written to and read from on a + regular basis. A second pool, + backup is used as a standby in case + the primary pool becomes unavailable. Note that this + fail-over is not done automatically by ZFS, + but must be manually done by a system administrator when + needed. A snapshot is used to provide a consistent version of + the file system to be replicated. Once a snapshot of + mypool has been created, it can be + copied to the backup pool. Only + snapshots can be replicated. Changes made since the most + recent snapshot will not be included. + + &prompt.root; zfs snapshot mypool@backup1 +&prompt.root; zfs list -t snapshot +NAME USED AVAIL REFER MOUNTPOINT +mypool@backup1 0 - 43.6M - + + Now that a snapshot exists, zfs send + can be used to create a stream representing the contents of + the snapshot. This stream can be stored as a file or received + by another pool. The stream is written to standard output, + but must be redirected to a file or pipe or an error is + produced: + + &prompt.root; zfs send mypool@backup1 +Error: Stream can not be written to a terminal. +You must redirect standard output. + + To back up a dataset with zfs send, + redirect to a file located on the mounted backup pool. Ensure + that the pool has enough free space to accommodate the size of + the snapshot being sent, which means all of the data contained + in the snapshot, not just the changes from the previous + snapshot. + + &prompt.root; zfs send mypool@backup1 > /backup/backup1 +&prompt.root; zpool list +NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT +backup 960M 63.7M 896M 6% 1.00x ONLINE - +mypool 984M 43.7M 940M 4% 1.00x ONLINE - + + The zfs send transferred all the data + in the snapshot called backup1 to + the pool named backup. Creating + and sending these snapshots can be done automatically with a + &man.cron.8; job. + + Instead of storing the backups as archive files, + ZFS can receive them as a live file system, + allowing the backed up data to be accessed directly. To get + to the actual data contained in those streams, + zfs receive is used to transform the + streams back into files and directories. The example below + combines zfs send and + zfs receive using a pipe to copy the data + from one pool to another. The data can be used directly on + the receiving pool after the transfer is complete. A dataset + can only be replicated to an empty dataset. + + &prompt.root; zfs snapshot mypool@replica1 +&prompt.root; zfs send -v mypool@replica1 | zfs receive backup/mypool +send from @ to mypool@replica1 estimated size is 50.1M +total estimated size is 50.1M +TIME SENT SNAPSHOT + +&prompt.root; zpool list +NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT +backup 960M 63.7M 896M 6% 1.00x ONLINE - +mypool 984M 43.7M 940M 4% 1.00x ONLINE - + + + Incremental Backups + + zfs send can also determine the + difference between two snapshots and send only the + differences between the two. This saves disk space and + transfer time. For example: + + &prompt.root; zfs snapshot mypool@replica2 +&prompt.root; zfs list -t snapshot +NAME USED AVAIL REFER MOUNTPOINT +mypool@replica1 5.72M - 43.6M - +mypool@replica2 0 - 44.1M - +&prompt.root; zpool list +NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT +backup 960M 61.7M 898M 6% 1.00x ONLINE - +mypool 960M 50.2M 910M 5% 1.00x ONLINE - + + A second snapshot called + replica2 was created. This + second snapshot contains only the changes that were made to + the file system between now and the previous snapshot, + replica1. Using + zfs send -i and indicating the pair of + snapshots generates an incremental replica stream containing + only the data that has changed. This can only succeed if + the initial snapshot already exists on the receiving + side. + + &prompt.root; zfs send -v -i mypool@replica1 mypool@replica2 | zfs receive /backup/mypool +send from @replica1 to mypool@replica2 estimated size is 5.02M +total estimated size is 5.02M +TIME SENT SNAPSHOT + +&prompt.root; zpool list +NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT +backup 960M 80.8M 879M 8% 1.00x ONLINE - +mypool 960M 50.2M 910M 5% 1.00x ONLINE - + +&prompt.root; zfs list +NAME USED AVAIL REFER MOUNTPOINT +backup 55.4M 240G 152K /backup +backup/mypool 55.3M 240G 55.2M /backup/mypool +mypool 55.6M 11.6G 55.0M /mypool + +&prompt.root; zfs list -t snapshot +NAME USED AVAIL REFER MOUNTPOINT +backup/mypool@replica1 104K - 50.2M - +backup/mypool@replica2 0 - 55.2M - +mypool@replica1 29.9K - 50.0M - +mypool@replica2 0 - 55.0M - + + The incremental stream was successfully transferred. + Only the data that had changed was replicated, rather than + the entirety of replica1. Only + the differences were sent, which took much less time to + transfer and saved disk space by not copying the complete + pool each time. This is useful when having to rely on slow + networks or when costs per transferred byte must be + considered. + + A new file system, + backup/mypool, is available with + all of the files and data from the pool + mypool. If + is specified, the properties of the dataset will be copied, + including compression settings, quotas, and mount points. + When is specified, all child datasets of + the indicated dataset will be copied, along with all of + their properties. Sending and receiving can be automated so + that regular backups are created on the second pool. + + + + Sending Encrypted Backups over + <application>SSH</application> + + Sending streams over the network is a good way to keep a + remote backup, but it does come with a drawback. Data sent + over the network link is not encrypted, allowing anyone to + intercept and transform the streams back into data without + the knowledge of the sending user. This is undesirable, + especially when sending the streams over the internet to a + remote host. SSH can be used to + securely encrypt data send over a network connection. Since + ZFS only requires the stream to be + redirected from standard output, it is relatively easy to + pipe it through SSH. To keep the + contents of the file system encrypted in transit and on the + remote system, consider using PEFS. + + A few settings and security precautions must be + completed first. Only the necessary steps required for the + zfs send operation are shown here. For + more information on SSH, see + . + + This configuration is required: + + + + Passwordless SSH access + between sending and receiving host using + SSH keys + + + + Normally, the privileges of the + root user are + needed to send and receive streams. This requires + logging in to the receiving system as + root. + However, logging in as + root is + disabled by default for security reasons. The + ZFS Delegation + system can be used to allow a + non-root user + on each system to perform the respective send and + receive operations. + + + + On the sending system: + + &prompt.root; zfs allow -u someuser send,snapshot mypool + + + + To mount the pool, the unprivileged user must own + the directory, and regular users must be allowed to + mount file systems. On the receiving system: + + &prompt.root; sysctl vfs.usermount=1 +vfs.usermount: 0 -> 1 +&prompt.root; echo vfs.usermount=1 >> /etc/sysctl.conf +&prompt.root; zfs create recvpool/backup +&prompt.root; zfs allow -u someuser create,mount,receive recvpool/backup +&prompt.root; chown someuser /recvpool/backup + + + + The unprivileged user now has the ability to receive and + mount datasets, and the home + dataset can be replicated to the remote system: + + &prompt.user; zfs snapshot -r mypool/home@monday +&prompt.user; zfs send -R mypool/home@monday | ssh someuser@backuphost zfs recv -dvu recvpool/backup + + A recursive snapshot called + monday is made of the file system + dataset home that resides on the + pool mypool. Then it is sent + with zfs send -R to include the dataset, + all child datasets, snaphots, clones, and settings in the + stream. The output is piped to the waiting + zfs receive on the remote host + backuphost through + SSH. Using a fully qualified + domain name or IP address is recommended. The receiving + machine writes the data to the + backup dataset on the + recvpool pool. Adding + to zfs recv + overwrites the name of the pool on the receiving side with + the name of the snapshot. causes the + file systems to not be mounted on the receiving side. When + is included, more detail about the + transfer is shown, including elapsed time and the amount of + data transferred. + + + + + Dataset, User, and Group Quotas + + Dataset quotas are + used to restrict the amount of space that can be consumed + by a particular dataset. + Reference Quotas work + in very much the same way, but only count the space + used by the dataset itself, excluding snapshots and child + datasets. Similarly, + user and + group quotas can be + used to prevent users or groups from using all of the + space in the pool or dataset. + + To enforce a dataset quota of 10 GB for + storage/home/bob: + + &prompt.root; zfs set quota=10G storage/home/bob + + To enforce a reference quota of 10 GB for + storage/home/bob: + + &prompt.root; zfs set refquota=10G storage/home/bob + + To remove a quota of 10 GB for + storage/home/bob: + + &prompt.root; zfs set quota=none storage/home/bob + + The general format is + userquota@user=size, + and the user's name must be in one of these formats: + + + + POSIX compatible name such as + joe. + + + + POSIX numeric ID such as + 789. + + + + SID name + such as + joe.bloggs@example.com. + + + + SID + numeric ID such as + S-1-123-456-789. + + + + For example, to enforce a user quota of 50 GB for the + user named joe: + + &prompt.root; zfs set userquota@joe=50G + + To remove any quota: + + &prompt.root; zfs set userquota@joe=none + + + User quota properties are not displayed by + zfs get all. + Non-root users can + only see their own quotas unless they have been granted the + userquota privilege. Users with this + privilege are able to view and set everyone's quota. + + + The general format for setting a group quota is: + groupquota@group=size. + + To set the quota for the group + firstgroup to 50 GB, + use: + + &prompt.root; zfs set groupquota@firstgroup=50G + + To remove the quota for the group + firstgroup, or to make sure that + one is not set, instead use: + + &prompt.root; zfs set groupquota@firstgroup=none + + As with the user quota property, + non-root users can + only see the quotas associated with the groups to which they + belong. However, + root or a user with + the groupquota privilege can view and set + all quotas for all groups. + + To display the amount of space used by each user on + a file system or snapshot along with any quotas, use + zfs userspace. For group information, use + zfs groupspace. For more information about + supported options or how to display only specific options, + refer to &man.zfs.1;. + + Users with sufficient privileges, and + root, can list the + quota for storage/home/bob using: + + &prompt.root; zfs get quota storage/home/bob + + + + Reservations + + Reservations + guarantee a minimum amount of space will always be available + on a dataset. The reserved space will not be available to any + other dataset. This feature can be especially useful to + ensure that free space is available for an important dataset + or log files. + + The general format of the reservation + property is + reservation=size, + so to set a reservation of 10 GB on + storage/home/bob, use: + + &prompt.root; zfs set reservation=10G storage/home/bob + + To clear any reservation: + + &prompt.root; zfs set reservation=none storage/home/bob + + The same principle can be applied to the + refreservation property for setting a + Reference + Reservation, with the general format + refreservation=size. + + This command shows any reservations or refreservations + that exist on storage/home/bob: + + &prompt.root; zfs get reservation storage/home/bob +&prompt.root; zfs get refreservation storage/home/bob + + + + Compression + + ZFS provides transparent compression. + Compressing data at the block level as it is written not only + saves space, but can also increase disk throughput. If data + is compressed by 25%, but the compressed data is written to + the disk at the same rate as the uncompressed version, + resulting in an effective write speed of 125%. Compression + can also be a great alternative to + Deduplication + because it does not require additional memory. + + ZFS offers several different + compression algorithms, each with different trade-offs. With + the introduction of LZ4 compression in + ZFS v5000, it is possible to enable + compression for the entire pool without the large performance + trade-off of other algorithms. The biggest advantage to + LZ4 is the early abort + feature. If LZ4 does not achieve at least + 12.5% compression in the first part of the data, the block is + written uncompressed to avoid wasting CPU cycles trying to + compress data that is either already compressed or + uncompressible. For details about the different compression + algorithms available in ZFS, see the + Compression entry + in the terminology section. + + The administrator can monitor the effectiveness of + compression using a number of dataset properties. + + &prompt.root; zfs get used,compressratio,compression,logicalused mypool/compressed_dataset +NAME PROPERTY VALUE SOURCE +mypool/compressed_dataset used 449G - +mypool/compressed_dataset compressratio 1.11x - +mypool/compressed_dataset compression lz4 local +mypool/compressed_dataset logicalused 496G - + + The dataset is currently using 449 GB of space (the + used property). Without compression, it would have taken + 496 GB of space (the logicallyused + property). This results in the 1.11:1 compression + ratio. + + Compression can have an unexpected side effect when + combined with + User Quotas. + User quotas restrict how much space a user can consume on a + dataset, but the measurements are based on how much space is + used after compression. So if a user has + a quota of 10 GB, and writes 10 GB of compressible + data, they will still be able to store additional data. If + they later update a file, say a database, with more or less + compressible data, the amount of space available to them will + change. This can result in the odd situation where a user did + not increase the actual amount of data (the + logicalused property), but the change in + compression caused them to reach their quota limit. + + Compression can have a similar unexpected interaction with + backups. Quotas are often used to limit how much data can be + stored to ensure there is sufficient backup space available. + However since quotas do not consider compression, more data + may be written than would fit with uncompressed + backups. + + + + Deduplication + + When enabled, + deduplication + uses the checksum of each block to detect duplicate blocks. + When a new block is a duplicate of an existing block, + ZFS writes an additional reference to the + existing data instead of the whole duplicate block. + Tremendous space savings are possible if the data contains + many duplicated files or repeated information. Be warned: + deduplication requires an extremely large amount of memory, + and most of the space savings can be had without the extra + cost by enabling compression instead. + + To activate deduplication, set the + dedup property on the target pool: + + &prompt.root; zfs set dedup=on pool + + Only new data being written to the pool will be + deduplicated. Data that has already been written to the pool + will not be deduplicated merely by activating this option. A + pool with a freshly activated deduplication property will look + like this example: + + &prompt.root; zpool list +NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT +pool 2.84G 2.19M 2.83G 0% 1.00x ONLINE - + + The DEDUP column shows the actual rate + of deduplication for the pool. A value of + 1.00x shows that data has not been + deduplicated yet. In the next example, the ports tree is + copied three times into different directories on the + deduplicated pool created above. + + &prompt.root; zpool list +for d in dir1 dir2 dir3; do +for> mkdir $d && cp -R /usr/ports $d & +for> done + + Redundant data is detected and deduplicated: + + &prompt.root; zpool list +NAME SIZE ALLOC FREE CAP DEDUP HEALTH ALTROOT +pool 2.84G 20.9M 2.82G 0% 3.00x ONLINE - + + The DEDUP column shows a factor of + 3.00x. Multiple copies of the ports tree + data was detected and deduplicated, using only a third of the + space. The potential for space savings can be enormous, but + comes at the cost of having enough memory to keep track of the + deduplicated blocks. + + Deduplication is not always beneficial, especially when + the data on a pool is not redundant. + ZFS can show potential space savings by + simulating deduplication on an existing pool: + + &prompt.root; zdb -S pool +Simulated DDT histogram: + +bucket allocated referenced +______ ______________________________ ______________________________ +refcnt blocks LSIZE PSIZE DSIZE blocks LSIZE PSIZE DSIZE +------ ------ ----- ----- ----- ------ ----- ----- ----- + 1 2.58M 289G 264G 264G 2.58M 289G 264G 264G + 2 206K 12.6G 10.4G 10.4G 430K 26.4G 21.6G 21.6G + 4 37.6K 692M 276M 276M 170K 3.04G 1.26G 1.26G + 8 2.18K 45.2M 19.4M 19.4M 20.0K 425M 176M 176M + 16 174 2.83M 1.20M 1.20M 3.33K 48.4M 20.4M 20.4M + 32 40 2.17M 222K 222K 1.70K 97.2M 9.91M 9.91M + 64 9 56K 10.5K 10.5K 865 4.96M 948K 948K + 128 2 9.50K 2K 2K 419 2.11M 438K 438K + 256 5 61.5K 12K 12K 1.90K 23.0M 4.47M 4.47M + 1K 2 1K 1K 1K 2.98K 1.49M 1.49M 1.49M + Total 2.82M 303G 275G 275G 3.20M 319G 287G 287G + +dedup = 1.05, compress = 1.11, copies = 1.00, dedup * compress / copies = 1.16 + + After zdb -S finishes analyzing the + pool, it shows the space reduction ratio that would be + achieved by activating deduplication. In this case, + 1.16 is a very poor space saving ratio that + is mostly provided by compression. Activating deduplication + on this pool would not save any significant amount of space, + and is not worth the amount of memory required to enable + deduplication. Using the formula + ratio = dedup * compress / copies, + system administrators can plan the storage allocation, + deciding whether the workload will contain enough duplicate + blocks to justify the memory requirements. If the data is + reasonably compressible, the space savings may be very good. + Enabling compression first is recommended, and compression can + also provide greatly increased performance. Only enable + deduplication in cases where the additional savings will be + considerable and there is sufficient memory for the DDT. + + + + <acronym>ZFS</acronym> and Jails + + zfs jail and the corresponding + jailed property are used to delegate a + ZFS dataset to a + Jail. + zfs jail jailid + attaches a dataset to the specified jail, and + zfs unjail detaches it. For the dataset to + be controlled from within a jail, the + jailed property must be set. Once a + dataset is jailed, it can no longer be mounted on the + host because it may have mount points that would compromise + the security of the host. + + + + + Delegated Administration + + A comprehensive permission delegation system allows + unprivileged users to perform ZFS + administration functions. For example, if each user's home + directory is a dataset, users can be given permission to create + and destroy snapshots of their home directories. A backup user + can be given permission to use replication features. A usage + statistics script can be allowed to run with access only to the + space utilization data for all users. It is even possible to + delegate the ability to delegate permissions. Permission + delegation is possible for each subcommand and most + properties. + + + Delegating Dataset Creation + + zfs allow + someuser create + mydataset gives the + specified user permission to create child datasets under the + selected parent dataset. There is a caveat: creating a new + dataset involves mounting it. That requires setting the + &os; vfs.usermount &man.sysctl.8; to + 1 to allow non-root users to mount a + file system. There is another restriction aimed at preventing + abuse: non-root + users must own the mountpoint where the file system is to be + mounted. + + + + Delegating Permission Delegation + + zfs allow + someuser allow + mydataset gives the + specified user the ability to assign any permission they have + on the target dataset, or its children, to other users. If a + user has the snapshot permission and the + allow permission, that user can then grant + the snapshot permission to other + users. + + + + + Advanced Topics + + + Tuning + + There are a number of tunables that can be adjusted to + make ZFS perform best for different + workloads. + + + + vfs.zfs.arc_max + - Maximum size of the ARC. + The default is all RAM less 1 GB, + or one half of RAM, whichever is more. + However, a lower value should be used if the system will + be running any other daemons or processes that may require + memory. This value can only be adjusted at boot time, and + is set in /boot/loader.conf. + + + + vfs.zfs.arc_meta_limit + - Limit the portion of the + ARC + that can be used to store metadata. The default is one + fourth of vfs.zfs.arc_max. Increasing + this value will improve performance if the workload + involves operations on a large number of files and + directories, or frequent metadata operations, at the cost + of less file data fitting in the ARC. + This value can only be adjusted at boot time, and is set + in /boot/loader.conf. + + + + vfs.zfs.arc_min + - Minimum size of the ARC. + The default is one half of + vfs.zfs.arc_meta_limit. Adjust this + value to prevent other applications from pressuring out + the entire ARC. + This value can only be adjusted at boot time, and is set + in /boot/loader.conf. + + + + vfs.zfs.vdev.cache.size + - A preallocated amount of memory reserved as a cache for + each device in the pool. The total amount of memory used + will be this value multiplied by the number of devices. + This value can only be adjusted at boot time, and is set + in /boot/loader.conf. + + + + vfs.zfs.min_auto_ashift + - Minimum ashift (sector size) that + will be used automatically at pool creation time. The + value is a power of two. The default value of + 9 represents + 2^9 = 512, a sector size of 512 bytes. + To avoid write amplification and get + the best performance, set this value to the largest sector + size used by a device in the pool. + + Many drives have 4 KB sectors. Using the default + ashift of 9 with + these drives results in write amplification on these + devices. Data that could be contained in a single + 4 KB write must instead be written in eight 512-byte + writes. ZFS tries to read the native + sector size from all devices when creating a pool, but + many drives with 4 KB sectors report that their + sectors are 512 bytes for compatibility. Setting + vfs.zfs.min_auto_ashift to + 12 (2^12 = 4096) + before creating a pool forces ZFS to + use 4 KB blocks for best performance on these + drives. + + Forcing 4 KB blocks is also useful on pools where + disk upgrades are planned. Future disks are likely to use + 4 KB sectors, and ashift values + cannot be changed after a pool is created. + + In some specific cases, the smaller 512-byte block + size might be preferable. When used with 512-byte disks + for databases, or as storage for virtual machines, less + data is transferred during small random reads. This can + provide better performance, especially when using a + smaller ZFS record size. + + + + vfs.zfs.prefetch_disable + - Disable prefetch. A value of 0 is + enabled and 1 is disabled. The default + is 0, unless the system has less than + 4 GB of RAM. Prefetch works by + reading larged blocks than were requested into the + ARC + in hopes that the data will be needed soon. If the + workload has a large number of random reads, disabling + prefetch may actually improve performance by reducing + unnecessary reads. This value can be adjusted at any time + with &man.sysctl.8;. + + + + vfs.zfs.vdev.trim_on_init + - Control whether new devices added to the pool have the + TRIM command run on them. This ensures + the best performance and longevity for + SSDs, but takes extra time. If the + device has already been secure erased, disabling this + setting will make the addition of the new device faster. + This value can be adjusted at any time with + &man.sysctl.8;. + + + + vfs.zfs.write_to_degraded + - Control whether new data is written to a vdev that is + in the DEGRADED + state. Defaults to 0, preventing + writes to any top level vdev that is in a degraded state. + The administrator may with to allow writing to degraded + vdevs to prevent the amount of free space across the vdevs + from becoming unbalanced, which will reduce read and write + performance. This value can be adjusted at any time with + &man.sysctl.8;. + + + + vfs.zfs.vdev.max_pending + - Limit the number of pending I/O requests per device. + A higher value will keep the device command queue full + and may give higher throughput. A lower value will reduce + latency. This value can be adjusted at any time with + &man.sysctl.8;. + + + + vfs.zfs.top_maxinflight + - Maxmimum number of outstanding I/Os per top-level + vdev. Limits the + depth of the command queue to prevent high latency. The + limit is per top-level vdev, meaning the limit applies to + each mirror, + RAID-Z, or + other vdev independently. This value can be adjusted at + any time with &man.sysctl.8;. + + + + vfs.zfs.l2arc_write_max + - Limit the amount of data written to the L2ARC + per second. This tunable is designed to extend the + longevity of SSDs by limiting the + amount of data written to the device. This value can be + adjusted at any time with &man.sysctl.8;. + + + + vfs.zfs.l2arc_write_boost + - The value of this tunable is added to vfs.zfs.l2arc_write_max + and increases the write speed to the + SSD until the first block is evicted + from the L2ARC. + This Turbo Warmup Phase is designed to + reduce the performance loss from an empty L2ARC + after a reboot. This value can be adjusted at any time + with &man.sysctl.8;. + + + + vfs.zfs.scrub_delay + - Number of ticks to delay between each I/O during a + scrub. + To ensure that a scrub does not + interfere with the normal operation of the pool, if any + other I/O is happening the + scrub will delay between each command. + This value controls the limit on the total + IOPS (I/Os Per Second) generated by the + scrub. The granularity of the setting + is deterined by the value of kern.hz + which defaults to 1000 ticks per second. This setting may + be changed, resulting in a different effective + IOPS limit. The default value is + 4, resulting in a limit of: + 1000 ticks/sec / 4 = + 250 IOPS. Using a value of + 20 would give a limit of: + 1000 ticks/sec / 20 = + 50 IOPS. The speed of + scrub is only limited when there has + been recent activity on the pool, as determined by vfs.zfs.scan_idle. + This value can be adjusted at any time with + &man.sysctl.8;. + + + + vfs.zfs.resilver_delay + - Number of milliseconds of delay inserted between + each I/O during a + resilver. To + ensure that a resilver does not interfere with the normal + operation of the pool, if any other I/O is happening the + resilver will delay between each command. This value + controls the limit of total IOPS (I/Os + Per Second) generated by the resilver. The granularity of + the setting is determined by the value of + kern.hz which defaults to 1000 ticks + per second. This setting may be changed, resulting in a + different effective IOPS limit. The + default value is 2, resulting in a limit of: + 1000 ticks/sec / 2 = + 500 IOPS. Returning the pool to + an Online state may + be more important if another device failing could + Fault the pool, + causing data loss. A value of 0 will give the resilver + operation the same priority as other operations, speeding + the healing process. The speed of resilver is only + limited when there has been other recent activity on the + pool, as determined by vfs.zfs.scan_idle. + This value can be adjusted at any time with + &man.sysctl.8;. + + + + vfs.zfs.scan_idle + - Number of milliseconds since the last operation before + the pool is considered idle. When the pool is idle the + rate limiting for scrub + and + resilver are + disabled. This value can be adjusted at any time with + &man.sysctl.8;. + + + + vfs.zfs.txg.timeout + - Maximum number of seconds between + transaction groups. + The current transaction group will be written to the pool + and a fresh transaction group started if this amount of + time has elapsed since the previous transaction group. A + transaction group my be triggered earlier if enough data + is written. The default value is 5 seconds. A larger + value may improve read performance by delaying + asynchronous writes, but this may cause uneven performance + when the transaction group is written. This value can be + adjusted at any time with &man.sysctl.8;. + + + + + + + + <acronym>ZFS</acronym> on i386 + + Some of the features provided by ZFS + are memory intensive, and may require tuning for maximum + efficiency on systems with limited + RAM. + + + Memory + + As a bare minimum, the total system memory should be at + least one gigabyte. The amount of recommended + RAM depends upon the size of the pool and + which ZFS features are used. A general + rule of thumb is 1 GB of RAM for every 1 TB of + storage. If the deduplication feature is used, a general + rule of thumb is 5 GB of RAM per TB of storage to be + deduplicated. While some users successfully use + ZFS with less RAM, + systems under heavy load may panic due to memory exhaustion. + Further tuning may be required for systems with less than + the recommended RAM requirements. + + + + Kernel Configuration + + Due to the address space limitations of the + &i386; platform, ZFS users on the + &i386; architecture must add this option to a + custom kernel configuration file, rebuild the kernel, and + reboot: + + options KVA_PAGES=512 + + This expands the kernel address space, allowing + the vm.kvm_size tunable to be pushed + beyond the currently imposed limit of 1 GB, or the + limit of 2 GB for PAE. To find the + most suitable value for this option, divide the desired + address space in megabytes by four. In this example, it + is 512 for 2 GB. + + + + Loader Tunables + + The kmem address space can be + increased on all &os; architectures. On a test system with + 1 GB of physical memory, success was achieved with + these options added to + /boot/loader.conf, and the system + restarted: + + vm.kmem_size="330M" +vm.kmem_size_max="330M" +vfs.zfs.arc_max="40M" +vfs.zfs.vdev.cache.size="5M" + + For a more detailed list of recommendations for + ZFS-related tuning, see . + + + + + + Additional Resources + + + + FreeBSD + Wiki - ZFS + + + + FreeBSD + Wiki - ZFS Tuning + + + + Illumos + Wiki - ZFS + + + + Oracle + Solaris ZFS Administration + Guide + + + + ZFS + Evil Tuning Guide + + + + ZFS + Best Practices Guide + + + + Calomel + Blog - ZFS Raidz Performance, Capacity + and Integrity + + + + + + <acronym>ZFS</acronym> Features and Terminology + + ZFS is a fundamentally different file + system because it is more than just a file system. + ZFS combines the roles of file system and + volume manager, enabling additional storage devices to be added + to a live system and having the new space available on all of + the existing file systems in that pool immediately. By + combining the traditionally separate roles, + ZFS is able to overcome previous limitations + that prevented RAID groups being able to + grow. Each top level device in a zpool is called a + vdev, which can be a simple disk or a + RAID transformation such as a mirror or + RAID-Z array. ZFS file + systems (called datasets) each have access + to the combined free space of the entire pool. As blocks are + allocated from the pool, the space available to each file system + decreases. This approach avoids the common pitfall with + extensive partitioning where free space becomes fragmented + across the partitions. + + + + + + zpool + + A storage pool is the most + basic building block of ZFS. A pool + is made up of one or more vdevs, the underlying devices + that store the data. A pool is then used to create one + or more file systems (datasets) or block devices + (volumes). These datasets and volumes share the pool of + remaining free space. Each pool is uniquely identified + by a name and a GUID. The features + available are determined by the ZFS + version number on the pool. + + + &os; 9.0 and 9.1 include support for + ZFS version 28. Later versions + use ZFS version 5000 with feature + flags. The new feature flags system allows greater + cross-compatibility with other implementations of + ZFS. + + + + + + vdev Types + + A pool is made up of one or more vdevs, which + themselves can be a single disk or a group of disks, in + the case of a RAID transform. When + multiple vdevs are used, ZFS spreads + data across the vdevs to increase performance and + maximize usable space. + + + + Disk + - The most basic type of vdev is a standard block + device. This can be an entire disk (such as + /dev/ada0 + or + /dev/da0) + or a partition + (/dev/ada0p3). + On &os;, there is no performance penalty for using + a partition rather than the entire disk. This + differs from recommendations made by the Solaris + documentation. + + + + File + - In addition to disks, ZFS + pools can be backed by regular files, this is + especially useful for testing and experimentation. + Use the full path to the file as the device path + in the zpool create command. All vdevs must be + at least 128 MB in size. + + + + Mirror + - When creating a mirror, specify the + mirror keyword followed by the + list of member devices for the mirror. A mirror + consists of two or more devices, all data will be + written to all member devices. A mirror vdev will + only hold as much data as its smallest member. A + mirror vdev can withstand the failure of all but + one of its members without losing any data. + + + A regular single disk vdev can be upgraded + to a mirror vdev at any time with + zpool + attach. + + + + + RAID-Z + - ZFS implements + RAID-Z, a variation on standard + RAID-5 that offers better + distribution of parity and eliminates the + RAID-5 write + hole in which the data and parity + information become inconsistent after an + unexpected restart. ZFS + supports three levels of RAID-Z + which provide varying levels of redundancy in + exchange for decreasing levels of usable storage. + The types are named RAID-Z1 + through RAID-Z3 based on the + number of parity devices in the array and the + number of disks which can fail while the pool + remains operational. + + In a RAID-Z1 configuration + with four disks, each 1 TB, usable storage is + 3 TB and the pool will still be able to + operate in degraded mode with one faulted disk. + If an additional disk goes offline before the + faulted disk is replaced and resilvered, all data + in the pool can be lost. + + In a RAID-Z3 configuration + with eight disks of 1 TB, the volume will + provide 5 TB of usable space and still be + able to operate with three faulted disks. &sun; + recommends no more than nine disks in a single + vdev. If the configuration has more disks, it is + recommended to divide them into separate vdevs and + the pool data will be striped across them. + + A configuration of two + RAID-Z2 vdevs consisting of 8 + disks each would create something similar to a + RAID-60 array. A + RAID-Z group's storage capacity + is approximately the size of the smallest disk + multiplied by the number of non-parity disks. + Four 1 TB disks in RAID-Z1 + has an effective size of approximately 3 TB, + and an array of eight 1 TB disks in + RAID-Z3 will yield 5 TB of + usable space. + + + + Spare + - ZFS has a special pseudo-vdev + type for keeping track of available hot spares. + Note that installed hot spares are not deployed + automatically; they must manually be configured to + replace the failed device using + zfs replace. + + + + Log + - ZFS Log Devices, also known + as ZFS Intent Log (ZIL) + move the intent log from the regular pool devices + to a dedicated device, typically an + SSD. Having a dedicated log + device can significantly improve the performance + of applications with a high volume of synchronous + writes, especially databases. Log devices can be + mirrored, but RAID-Z is not + supported. If multiple log devices are used, + writes will be load balanced across them. + + + + Cache + - Adding a cache vdev to a zpool will add the + storage of the cache to the L2ARC. + Cache devices cannot be mirrored. Since a cache + device only stores additional copies of existing + data, there is no risk of data loss. + + + + + + Transaction Group + (TXG) + + Transaction Groups are the way changed blocks are + grouped together and eventually written to the pool. + Transaction groups are the atomic unit that + ZFS uses to assert consistency. Each + transaction group is assigned a unique 64-bit + consecutive identifier. There can be up to three active + transaction groups at a time, one in each of these three + states: + + + + Open - When a new + transaction group is created, it is in the open + state, and accepts new writes. There is always + a transaction group in the open state, however the + transaction group may refuse new writes if it has + reached a limit. Once the open transaction group + has reached a limit, or the vfs.zfs.txg.timeout + has been reached, the transaction group advances + to the next state. + + + + Quiescing - A short state + that allows any pending operations to finish while + not blocking the creation of a new open + transaction group. Once all of the transactions + in the group have completed, the transaction group + advances to the final state. + + + + Syncing - All of the data + in the transaction group is written to stable + storage. This process will in turn modify other + data, such as metadata and space maps, that will + also need to be written to stable storage. The + process of syncing involves multiple passes. The + first, all of the changed data blocks, is the + biggest, followed by the metadata, which may take + multiple passes to complete. Since allocating + space for the data blocks generates new metadata, + the syncing state cannot finish until a pass + completes that does not allocate any additional + space. The syncing state is also where + synctasks are completed. + Synctasks are administrative operations, such as + creating or destroying snapshots and datasets, + that modify the uberblock are completed. Once the + sync state is complete, the transaction group in + the quiescing state is advanced to the syncing + state. + + + + All administrative functions, such as snapshot + are written as part of the transaction group. When a + synctask is created, it is added to the currently open + transaction group, and that group is advanced as quickly + as possible to the syncing state to reduce the + latency of administrative commands. + + + + Adaptive Replacement + Cache (ARC) + + ZFS uses an Adaptive Replacement + Cache (ARC), rather than a more + traditional Least Recently Used (LRU) + cache. An LRU cache is a simple list + of items in the cache, sorted by when each object was + most recently used. New items are added to the top of + the list. When the cache is full, items from the + bottom of the list are evicted to make room for more + active objects. An ARC consists of + four lists; the Most Recently Used + (MRU) and Most Frequently Used + (MFU) objects, plus a ghost list for + each. These ghost lists track recently evicted objects + to prevent them from being added back to the cache. + This increases the cache hit ratio by avoiding objects + that have a history of only being used occasionally. + Another advantage of using both an + MRU and MFU is + that scanning an entire file system would normally evict + all data from an MRU or + LRU cache in favor of this freshly + accessed content. With ZFS, there is + also an MFU that only tracks the most + frequently used objects, and the cache of the most + commonly accessed blocks remains. + + + + L2ARC + + L2ARC is the second level + of the ZFS caching system. The + primary ARC is stored in + RAM. Since the amount of + available RAM is often limited, + ZFS can also use + cache vdevs. + Solid State Disks (SSDs) are often + used as these cache devices due to their higher speed + and lower latency compared to traditional spinning + disks. L2ARC is entirely optional, + but having one will significantly increase read speeds + for files that are cached on the SSD + instead of having to be read from the regular disks. + L2ARC can also speed up deduplication + because a DDT that does not fit in + RAM but does fit in the + L2ARC will be much faster than a + DDT that must be read from disk. The + rate at which data is added to the cache devices is + limited to prevent prematurely wearing out + SSDs with too many writes. Until the + cache is full (the first block has been evicted to make + room), writing to the L2ARC is + limited to the sum of the write limit and the boost + limit, and afterwards limited to the write limit. A + pair of &man.sysctl.8; values control these rate limits. + vfs.zfs.l2arc_write_max + controls how many bytes are written to the cache per + second, while vfs.zfs.l2arc_write_boost + adds to this limit during the + Turbo Warmup Phase (Write Boost). + + + + ZIL + + ZIL accelerates synchronous + transactions by using storage devices like + SSDs that are faster than those used + in the main storage pool. When an application requests + a synchronous write (a guarantee that the data has been + safely stored to disk rather than merely cached to be + written later), the data is written to the faster + ZIL storage, then later flushed out + to the regular disks. This greatly reduces latency and + improves performance. Only synchronous workloads like + databases will benefit from a ZIL. + Regular asynchronous writes such as copying files will + not use the ZIL at all. + + + + Copy-On-Write + + Unlike a traditional file system, when data is + overwritten on ZFS, the new data is + written to a different block rather than overwriting the + old data in place. Only when this write is complete is + the metadata then updated to point to the new location. + In the event of a shorn write (a system crash or power + loss in the middle of writing a file), the entire + original contents of the file are still available and + the incomplete write is discarded. This also means that + ZFS does not require a &man.fsck.8; + after an unexpected shutdown. + + + + Dataset + + Dataset is the generic term + for a ZFS file system, volume, + snapshot or clone. Each dataset has a unique name in + the format + poolname/path@snapshot. + The root of the pool is technically a dataset as well. + Child datasets are named hierarchically like + directories. For example, + mypool/home, the home + dataset, is a child of mypool + and inherits properties from it. This can be expanded + further by creating + mypool/home/user. This + grandchild dataset will inherit properties from the + parent and grandparent. Properties on a child can be + set to override the defaults inherited from the parents + and grandparents. Administration of datasets and their + children can be + delegated. + + + + File system + + A ZFS dataset is most often used + as a file system. Like most other file systems, a + ZFS file system is mounted somewhere + in the systems directory hierarchy and contains files + and directories of its own with permissions, flags, and + other metadata. + + + + Volume + + In additional to regular file system datasets, + ZFS can also create volumes, which + are block devices. Volumes have many of the same + features, including copy-on-write, snapshots, clones, + and checksumming. Volumes can be useful for running + other file system formats on top of + ZFS, such as UFS + virtualization, or exporting iSCSI + extents. + + + + Snapshot + + The + copy-on-write + (COW) design of + ZFS allows for nearly instantaneous, + consistent snapshots with arbitrary names. After taking + a snapshot of a dataset, or a recursive snapshot of a + parent dataset that will include all child datasets, new + data is written to new blocks, but the old blocks are + not reclaimed as free space. The snapshot contains + the original version of the file system, and the live + file system contains any changes made since the snapshot + was taken. No additional space is used. As new data is + written to the live file system, new blocks are + allocated to store this data. The apparent size of the + snapshot will grow as the blocks are no longer used in + the live file system, but only in the snapshot. These + snapshots can be mounted read only to allow for the + recovery of previous versions of files. It is also + possible to + rollback a live + file system to a specific snapshot, undoing any changes + that took place after the snapshot was taken. Each + block in the pool has a reference counter which keeps + track of how many snapshots, clones, datasets, or + volumes make use of that block. As files and snapshots + are deleted, the reference count is decremented. When a + block is no longer referenced, it is reclaimed as free + space. Snapshots can also be marked with a + hold. When a + snapshot is held, any attempt to destroy it will return + an EBUSY error. Each snapshot can + have multiple holds, each with a unique name. The + release command + removes the hold so the snapshot can deleted. Snapshots + can be taken on volumes, but they can only be cloned or + rolled back, not mounted independently. + + + + Clone + + Snapshots can also be cloned. A clone is a + writable version of a snapshot, allowing the file system + to be forked as a new dataset. As with a snapshot, a + clone initially consumes no additional space. As + new data is written to a clone and new blocks are + allocated, the apparent size of the clone grows. When + blocks are overwritten in the cloned file system or + volume, the reference count on the previous block is + decremented. The snapshot upon which a clone is based + cannot be deleted because the clone depends on it. The + snapshot is the parent, and the clone is the child. + Clones can be promoted, reversing + this dependency and making the clone the parent and the + previous parent the child. This operation requires no + additional space. Because the amount of space used by + the parent and child is reversed, existing quotas and + reservations might be affected. + + + + Checksum + + Every block that is allocated is also checksummed. + The checksum algorithm used is a per-dataset property, + see set. + The checksum of each block is transparently validated as + it is read, allowing ZFS to detect + silent corruption. If the data that is read does not + match the expected checksum, ZFS will + attempt to recover the data from any available + redundancy, like mirrors or RAID-Z). + Validation of all checksums can be triggered with scrub. + Checksum algorithms include: + + + + fletcher2 + + + + fletcher4 + + + + sha256 + + + + The fletcher algorithms are faster, + but sha256 is a strong cryptographic + hash and has a much lower chance of collisions at the + cost of some performance. Checksums can be disabled, + but it is not recommended. + + + + Compression + + Each dataset has a compression property, which + defaults to off. This property can be set to one of a + number of compression algorithms. This will cause all + new data that is written to the dataset to be + compressed. Beyond a reduction in space used, read and + write throughput often increases because fewer blocks + are read or written. + + + + LZ4 - + Added in ZFS pool version + 5000 (feature flags), LZ4 is + now the recommended compression algorithm. + LZ4 compresses approximately + 50% faster than LZJB when + operating on compressible data, and is over three + times faster when operating on uncompressible + data. LZ4 also decompresses + approximately 80% faster than + LZJB. On modern + CPUs, LZ4 + can often compress at over 500 MB/s, and + decompress at over 1.5 GB/s (per single CPU + core). + + + LZ4 compression is + only available after &os; 9.2. + + + + + LZJB - + The default compression algorithm. Created by + Jeff Bonwick (one of the original creators of + ZFS). LZJB + offers good compression with less + CPU overhead compared to + GZIP. In the future, the + default compression algorithm will likely change + to LZ4. + + + + GZIP - + A popular stream compression algorithm available + in ZFS. One of the main + advantages of using GZIP is its + configurable level of compression. When setting + the compress property, the + administrator can choose the level of compression, + ranging from gzip1, the lowest + level of compression, to gzip9, + the highest level of compression. This gives the + administrator control over how much + CPU time to trade for saved + disk space. + + + + ZLE - + Zero Length Encoding is a special compression + algorithm that only compresses continuous runs of + zeros. This compression algorithm is only useful + when the dataset contains large blocks of + zeros. + + + + + + Copies + + When set to a value greater than 1, the + copies property instructs + ZFS to maintain multiple copies of + each block in the + File System + or + Volume. Setting + this property on important datasets provides additional + redundancy from which to recover a block that does not + match its checksum. In pools without redundancy, the + copies feature is the only form of redundancy. The + copies feature can recover from a single bad sector or + other forms of minor corruption, but it does not protect + the pool from the loss of an entire disk. + + + + Deduplication + + Checksums make it possible to detect duplicate + blocks of data as they are written. With deduplication, + the reference count of an existing, identical block is + increased, saving storage space. To detect duplicate + blocks, a deduplication table (DDT) + is kept in memory. The table contains a list of unique + checksums, the location of those blocks, and a reference + count. When new data is written, the checksum is + calculated and compared to the list. If a match is + found, the existing block is used. The + SHA256 checksum algorithm is used + with deduplication to provide a secure cryptographic + hash. Deduplication is tunable. If + dedup is on, then + a matching checksum is assumed to mean that the data is + identical. If dedup is set to + verify, then the data in the two + blocks will be checked byte-for-byte to ensure it is + actually identical. If the data is not identical, the + hash collision will be noted and the two blocks will be + stored separately. Because DDT must + store the hash of each unique block, it consumes a very + large amount of memory. A general rule of thumb is + 5-6 GB of ram per 1 TB of deduplicated data). + In situations where it is not practical to have enough + RAM to keep the entire + DDT in memory, performance will + suffer greatly as the DDT must be + read from disk before each new block is written. + Deduplication can use L2ARC to store + the DDT, providing a middle ground + between fast system memory and slower disks. Consider + using compression instead, which often provides nearly + as much space savings without the additional memory + requirement. + + + + Scrub + + Instead of a consistency check like &man.fsck.8;, + ZFS has scrub. + scrub reads all data blocks stored on + the pool and verifies their checksums against the known + good checksums stored in the metadata. A periodic check + of all the data stored on the pool ensures the recovery + of any corrupted blocks before they are needed. A scrub + is not required after an unclean shutdown, but is + recommended at least once every three months. The + checksum of each block is verified as blocks are read + during normal use, but a scrub makes certain that even + infrequently used blocks are checked for silent + corruption. Data security is improved, especially in + archival storage situations. The relative priority of + scrub can be adjusted with vfs.zfs.scrub_delay + to prevent the scrub from degrading the performance of + other workloads on the pool. + + + + Dataset Quota + + ZFS provides very fast and + accurate dataset, user, and group space accounting in + addition to quotas and space reservations. This gives + the administrator fine grained control over how space is + allocated and allows space to be reserved for critical + file systems. + + ZFS supports different types of + quotas: the dataset quota, the reference + quota (refquota), the + user + quota, and the + group + quota. + + Quotas limit the amount of space that a dataset + and all of its descendants, including snapshots of the + dataset, child datasets, and the snapshots of those + datasets, can consume. + + + Quotas cannot be set on volumes, as the + volsize property acts as an + implicit quota. + + + + + Reference + Quota + + A reference quota limits the amount of space a + dataset can consume by enforcing a hard limit. However, + this hard limit includes only space that the dataset + references and does not include space used by + descendants, such as file systems or snapshots. + + + + User + Quota + + User quotas are useful to limit the amount of space + that can be used by the specified user. + + + + Group + Quota + + The group quota limits the amount of space that a + specified group can consume. + + + + Dataset + Reservation + + The reservation property makes + it possible to guarantee a minimum amount of space for a + specific dataset and its descendants. If a 10 GB + reservation is set on + storage/home/bob, and another + dataset tries to use all of the free space, at least + 10 GB of space is reserved for this dataset. If a + snapshot is taken of + storage/home/bob, the space used by + that snapshot is counted against the reservation. The + refreservation + property works in a similar way, but it + excludes descendants like + snapshots. + + Reservations of any sort are useful in many + situations, such as planning and testing the + suitability of disk space allocation in a new system, + or ensuring that enough space is available on file + systems for audio logs or system recovery procedures + and files. + + + + + Reference + Reservation + + The refreservation property + makes it possible to guarantee a minimum amount of + space for the use of a specific dataset + excluding its descendants. This + means that if a 10 GB reservation is set on + storage/home/bob, and another + dataset tries to use all of the free space, at least + 10 GB of space is reserved for this dataset. In + contrast to a regular + reservation, + space used by snapshots and decendant datasets is not + counted against the reservation. For example, if a + snapshot is taken of + storage/home/bob, enough disk space + must exist outside of the + refreservation amount for the + operation to succeed. Descendants of the main data set + are not counted in the refreservation + amount and so do not encroach on the space set. + + + + Resilver + + When a disk fails and is replaced, the new disk + must be filled with the data that was lost. The process + of using the parity information distributed across the + remaining drives to calculate and write the missing data + to the new drive is called + resilvering. + + + + Online + + A pool or vdev in the Online + state has all of its member devices connected and fully + operational. Individual devices in the + Online state are functioning + normally. + + + + Offline + + Individual devices can be put in an + Offline state by the administrator if + there is sufficient redundancy to avoid putting the pool + or vdev into a + Faulted state. + An administrator may choose to offline a disk in + preparation for replacing it, or to make it easier to + identify. + + + + Degraded + + A pool or vdev in the Degraded + state has one or more disks that have been disconnected + or have failed. The pool is still usable, but if + additional devices fail, the pool could become + unrecoverable. Reconnecting the missing devices or + replacing the failed disks will return the pool to an + Online state + after the reconnected or new device has completed the + Resilver + process. + + + + Faulted + + A pool or vdev in the Faulted + state is no longer operational. The data on it can no + longer be accessed. A pool or vdev enters the + Faulted state when the number of + missing or failed devices exceeds the level of + redundancy in the vdev. If missing devices can be + reconnected, the pool will return to a + Online state. If + there is insufficient redundancy to compensate for the + number of failed disks, then the contents of the pool + are lost and must be restored from backups. + + + + + + Property changes on: head/en_US.ISO8859-1/books/handbook/zfs/chapter.xml ___________________________________________________________________ Added: svn:eol-style ## -0,0 +1 ## +native \ No newline at end of property Added: svn:keywords ## -0,0 +1 ## +FreeBSD=%H \ No newline at end of property Added: svn:mime-type ## -0,0 +1 ## +text/xml \ No newline at end of property