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&dtrace;TomRhodesWritten
by Synopsis&dtrace;&dtrace; support&dtrace;&dtrace;, also known as Dynamic Tracing, was developed by
&sun; as a tool for locating performance bottlenecks in
production and pre-production systems. In addition to
diagnosing performance problems, &dtrace; can be used to help
investigate and debug unexpected behavior in both the &os;
kernel and in userland programs.&dtrace; is a remarkable profiling tool, with an impressive
array of features for diagnosing system issues. It may also be
used to run pre-written scripts to take advantage of its
capabilities. Users can author their own utilities using the
&dtrace; D Language, allowing them to customize their profiling
based on specific needs.The &os; implementation provides full support for kernel
&dtrace; and experimental support for userland &dtrace;.
Userland &dtrace; allows users to perform function boundary
tracing for userland programs using the pid
provider, and to insert static probes into userland programs for
later tracing. Some ports, such as
databases/postgres-server and
- lang/php5 have a &dtrace; option to enable
+ lang/php56 have a &dtrace; option to enable
static probes. &os; 10.0-RELEASE has reasonably good userland
&dtrace; support, but it is not considered production ready. In
particular, it is possible to crash traced programs.The official guide to DTrace is maintained by the Illumos
project at DTrace
Guide.After reading this chapter, you will know:What &dtrace; is and what features it provides.Differences between the &solaris; &dtrace;
implementation and the one provided by &os;.How to enable and use &dtrace; on &os;.Before reading this chapter, you should:Understand &unix; and &os; basics
().Have some familiarity with security and how it pertains
to &os; ().Implementation DifferencesWhile the &dtrace; in &os; is similar to that found in
&solaris;, differences do exist. The primary difference is that
in &os;, &dtrace; is implemented as a set of kernel modules and
&dtrace; can not be used until the modules are loaded. To load
all of the necessary modules:&prompt.root; kldload dtraceallBeginning with &os; 10.0-RELEASE, the modules are
automatically loaded when dtrace is
run.&os; uses the DDB_CTF kernel option to
enable support for loading CTF data from
kernel modules and the kernel itself. CTF is
the &solaris; Compact C Type Format which encapsulates a reduced
form of debugging information similar to
DWARF and the venerable stabs.
CTF data is added to binaries by the
ctfconvert and ctfmerge
build tools. The ctfconvert utility parses
DWARF ELF debug sections
created by the compiler and ctfmerge merges
CTF ELF sections from
objects into either executables or shared libraries.Some different providers exist for &os; than for &solaris;.
Most notable is the dtmalloc provider, which
allows tracing malloc() by type in the &os;
kernel. Some of the providers found in &solaris;, such as
cpc and mib, are not
present in &os;. These may appear in future versions of &os;.
Moreover, some of the providers available in both operating
systems are not compatible, in the sense that their probes have
different argument types. Thus, D scripts
written on &solaris; may or may not work unmodified on &os;, and
vice versa.Due to security differences, only root may use &dtrace; on &os;.
&solaris; has a few low level security checks which do not yet
exist in &os;. As such, the
/dev/dtrace/dtrace is strictly limited to
root.&dtrace; falls under the Common Development and Distribution
License (CDDL) license. To view this license
on &os;, see
/usr/src/cddl/contrib/opensolaris/OPENSOLARIS.LICENSE
or view it online at http://opensource.org/licenses/CDDL-1.0.
While a &os; kernel with &dtrace; support is
BSD licensed, the CDDL is
used when the modules are distributed in binary form or the
binaries are loaded.Enabling &dtrace; SupportIn &os; 9.2 and 10.0, &dtrace; support is built into the
GENERIC kernel. Users of earlier versions
of &os; or who prefer to statically compile in &dtrace; support
should add the following lines to a custom kernel configuration
file and recompile the kernel using the instructions in :options KDTRACE_HOOKS
options DDB_CTF
makeoptions DEBUG=-g
makeoptions WITH_CTF=1Users of the AMD64 architecture should also add this
line:options KDTRACE_FRAMEThis option provides support for FBT.
While &dtrace; will work without this option, there will be
limited support for function boundary tracing.Once the &os; system has rebooted into the new kernel, or
the &dtrace; kernel modules have been loaded using
kldload dtraceall, the system will need
support for the Korn shell as the &dtrace;
Toolkit has several utilities written in ksh.
Make sure that the shells/ksh93 package or
port is installed. It is also possible to run these tools under
shells/pdksh or
shells/mksh.Finally, install the current &dtrace; Toolkit,
a collection of ready-made scripts
for collecting system information. There are scripts to check
open files, memory, CPU usage, and a lot
more. &os; 10
installs a few of these scripts into
/usr/share/dtrace. On other &os; versions,
or to install the full
&dtrace; Toolkit, use the
sysutils/DTraceToolkit package or
port.The scripts found in
/usr/share/dtrace have been specifically
ported to &os;. Not all of the scripts found in the &dtrace;
Toolkit will work as-is on &os; and some scripts may require
some effort in order for them to work on &os;.The &dtrace; Toolkit includes many scripts in the special
language of &dtrace;. This language is called the D language
and it is very similar to C++. An in depth discussion of the
language is beyond the scope of this document. It is
extensively discussed at http://wikis.oracle.com/display/DTrace/Documentation.Using &dtrace;&dtrace; scripts consist of a list of one or more
probes, or instrumentation points, where
each probe is associated with an action. Whenever the condition
for a probe is met, the associated action is executed. For
example, an action may occur when a file is opened, a process is
started, or a line of code is executed. The action might be to
log some information or to modify context variables. The
reading and writing of context variables allows probes to share
information and to cooperatively analyze the correlation of
different events.To view all probes, the administrator can execute the
following command:&prompt.root; dtrace -l | moreEach probe has an ID, a
PROVIDER (dtrace or fbt), a
MODULE, and a
FUNCTION NAME. Refer to &man.dtrace.1; for
more information about this command.The examples in this section provide an overview of how to
use two of the fully supported scripts from the
&dtrace; Toolkit: the
hotkernel and
procsystime scripts.The hotkernel script is designed to
identify which function is using the most kernel time. It will
produce output similar to the following:&prompt.root; cd /usr/share/dtrace/toolkit
&prompt.root; ./hotkernel
Sampling... Hit Ctrl-C to end.As instructed, use the
CtrlC key combination to stop the process. Upon
termination, the script will display a list of kernel functions
and timing information, sorting the output in increasing order
of time:kernel`_thread_lock_flags 2 0.0%
0xc1097063 2 0.0%
kernel`sched_userret 2 0.0%
kernel`kern_select 2 0.0%
kernel`generic_copyin 3 0.0%
kernel`_mtx_assert 3 0.0%
kernel`vm_fault 3 0.0%
kernel`sopoll_generic 3 0.0%
kernel`fixup_filename 4 0.0%
kernel`_isitmyx 4 0.0%
kernel`find_instance 4 0.0%
kernel`_mtx_unlock_flags 5 0.0%
kernel`syscall 5 0.0%
kernel`DELAY 5 0.0%
0xc108a253 6 0.0%
kernel`witness_lock 7 0.0%
kernel`read_aux_data_no_wait 7 0.0%
kernel`Xint0x80_syscall 7 0.0%
kernel`witness_checkorder 7 0.0%
kernel`sse2_pagezero 8 0.0%
kernel`strncmp 9 0.0%
kernel`spinlock_exit 10 0.0%
kernel`_mtx_lock_flags 11 0.0%
kernel`witness_unlock 15 0.0%
kernel`sched_idletd 137 0.3%
0xc10981a5 42139 99.3%This script will also work with kernel modules. To use this
feature, run the script with :&prompt.root; ./hotkernel -m
Sampling... Hit Ctrl-C to end.
^C
MODULE COUNT PCNT
0xc107882e 1 0.0%
0xc10e6aa4 1 0.0%
0xc1076983 1 0.0%
0xc109708a 1 0.0%
0xc1075a5d 1 0.0%
0xc1077325 1 0.0%
0xc108a245 1 0.0%
0xc107730d 1 0.0%
0xc1097063 2 0.0%
0xc108a253 73 0.0%
kernel 874 0.4%
0xc10981a5 213781 99.6%The procsystime script captures and
prints the system call time usage for a given process
ID (PID) or process name.
In the following example, a new instance of
/bin/csh was spawned. Then,
procsystime was executed and remained
waiting while a few commands were typed on the other incarnation
of csh. These are the results of this
test:&prompt.root; ./procsystime -n csh
Tracing... Hit Ctrl-C to end...
^C
Elapsed Times for processes csh,
SYSCALL TIME (ns)
getpid 6131
sigreturn 8121
close 19127
fcntl 19959
dup 26955
setpgid 28070
stat 31899
setitimer 40938
wait4 62717
sigaction 67372
sigprocmask 119091
gettimeofday 183710
write 263242
execve 492547
ioctl 770073
vfork 3258923
sigsuspend 6985124
read 3988049784As shown, the read() system call used
the most time in nanoseconds while the
getpid() system call used the least amount
of time.
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Network ServersSynopsisThis chapter covers some of the more frequently used network
services on &unix; systems. This includes installing,
configuring, testing, and maintaining many different types of
network services. Example configuration files are included
throughout this chapter for reference.By the end of this chapter, readers will know:How to manage the inetd
daemon.How to set up the Network File System
(NFS).How to set up the Network Information Server
(NIS) for centralizing and sharing
user accounts.How to set &os; up to act as an LDAP
server or clientHow to set up automatic network settings using
DHCP.How to set up a Domain Name Server
(DNS).How to set up the Apache
HTTP Server.How to set up a File Transfer Protocol
(FTP) server.How to set up a file and print server for &windows;
clients using Samba.How to synchronize the time and date, and set up a
time server using the Network Time Protocol
(NTP).How to set up iSCSI.This chapter assumes a basic knowledge of:/etc/rc scripts.Network terminology.Installation of additional third-party
software ().The inetd
Super-ServerThe &man.inetd.8; daemon is sometimes referred to as a
Super-Server because it manages connections for many services.
Instead of starting multiple applications, only the
inetd service needs to be started.
When a connection is received for a service that is managed by
inetd, it determines which program
the connection is destined for, spawns a process for that
program, and delegates the program a socket. Using
inetd for services that are not
heavily used can reduce system load, when compared to running
each daemon individually in stand-alone mode.Primarily, inetd is used to
spawn other daemons, but several trivial protocols are handled
internally, such as chargen,
auth,
time,
echo,
discard, and
daytime.This section covers the basics of configuring
inetd.Configuration FileConfiguration of inetd is
done by editing /etc/inetd.conf. Each
line of this configuration file represents an application
which can be started by inetd. By
default, every line starts with a comment
(#), meaning that
inetd is not listening for any
applications. To configure inetd
to listen for an application's connections, remove the
# at the beginning of the line for that
application.After saving your edits, configure
inetd to start at system boot by
editing /etc/rc.conf:inetd_enable="YES"To start inetd now, so that it
listens for the service you configured, type:&prompt.root; service inetd startOnce inetd is started, it needs
to be notified whenever a modification is made to
/etc/inetd.conf:Reloading the inetd
Configuration File&prompt.root; service inetd reloadTypically, the default entry for an application does not
need to be edited beyond removing the #.
In some situations, it may be appropriate to edit the default
entry.As an example, this is the default entry for &man.ftpd.8;
over IPv4:ftp stream tcp nowait root /usr/libexec/ftpd ftpd -lThe seven columns in an entry are as follows:service-name
socket-type
protocol
{wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]]
user[:group][/login-class]
server-program
server-program-argumentswhere:service-nameThe service name of the daemon to start. It must
correspond to a service listed in
/etc/services. This determines
which port inetd listens on
for incoming connections to that service. When using a
custom service, it must first be added to
/etc/services.socket-typeEither stream,
dgram, raw, or
seqpacket. Use
stream for TCP connections and
dgram for
UDP services.protocolUse one of the following protocol names:Protocol NameExplanationtcp or tcp4TCP IPv4udp or udp4UDP IPv4tcp6TCP IPv6udp6UDP IPv6tcp46Both TCP IPv4 and IPv6udp46Both UDP IPv4 and
IPv6{wait|nowait}[/max-child[/max-connections-per-ip-per-minute[/max-child-per-ip]]]In this field, or
must be specified.
,
and
are optional. indicates whether or
not the service is able to handle its own socket.
socket types must use
while
daemons, which are usually
multi-threaded, should use .
usually hands off multiple sockets
to a single daemon, while spawns
a child daemon for each new socket.The maximum number of child daemons
inetd may spawn is set by
. For example, to limit ten
instances of the daemon, place a /10
after . Specifying
/0 allows an unlimited number of
children.
limits the number of connections from any particular
IP address per minute. Once the
limit is reached, further connections from this IP
address will be dropped until the end of the minute.
For example, a value of /10 would
limit any particular IP address to
ten connection attempts per minute.
limits the number of
child processes that can be started on behalf on any
single IP address at any moment.
These options can limit excessive resource consumption
and help to prevent Denial of Service attacks.An example can be seen in the default settings for
&man.fingerd.8;:finger stream tcp nowait/3/10 nobody /usr/libexec/fingerd fingerd -k -suserThe username the daemon
will run as. Daemons typically run as
root,
daemon, or
nobody.server-programThe full path to the daemon. If the daemon is a
service provided by inetd
internally, use .server-program-argumentsUsed to specify any command arguments to be passed
to the daemon on invocation. If the daemon is an
internal service, use
.Command-Line OptionsLike most server daemons, inetd
has a number of options that can be used to modify its
behaviour. By default, inetd is
started with -wW -C 60. These options
enable TCP wrappers for all services, including internal
services, and prevent any IP address from
requesting any service more than 60 times per minute.To change the default options which are passed to
inetd, add an entry for
inetd_flags in
/etc/rc.conf. If
inetd is already running, restart
it with service inetd restart.The available rate limiting options are:-c maximumSpecify the default maximum number of simultaneous
invocations of each service, where the default is
unlimited. May be overridden on a per-service basis by
using in
/etc/inetd.conf.-C rateSpecify the default maximum number of times a
service can be invoked from a single
IP address per minute. May be
overridden on a per-service basis by using
in
/etc/inetd.conf.-R rateSpecify the maximum number of times a service can be
invoked in one minute, where the default is
256. A rate of 0
allows an unlimited number.-s maximumSpecify the maximum number of times a service can be
invoked from a single IP address at
any one time, where the default is unlimited. May be
overridden on a per-service basis by using
in
/etc/inetd.conf.Additional options are available. Refer to &man.inetd.8;
for the full list of options.Security ConsiderationsMany of the daemons which can be managed by
inetd are not security-conscious.
Some daemons, such as fingerd, can
provide information that may be useful to an attacker. Only
enable the services which are needed and monitor the system
for excessive connection attempts.
max-connections-per-ip-per-minute,
max-child and
max-child-per-ip can be used to limit such
attacks.By default, TCP wrappers is enabled. Consult
&man.hosts.access.5; for more information on placing TCP
restrictions on various
inetd invoked daemons.Network File System (NFS)TomRhodesReorganized and enhanced by BillSwingleWritten by NFS&os; supports the Network File System
(NFS), which allows a server to share
directories and files with clients over a network. With
NFS, users and programs can access files on
remote systems as if they were stored locally.NFS has many practical uses. Some of
the more common uses include:Data that would otherwise be duplicated on each client
can be kept in a single location and accessed by clients
on the network.Several clients may need access to the
/usr/ports/distfiles directory.
Sharing that directory allows for quick access to the
source files without having to download them to each
client.On large networks, it is often more convenient to
configure a central NFS server on which
all user home directories are stored. Users can log into
a client anywhere on the network and have access to their
home directories.Administration of NFS exports is
simplified. For example, there is only one file system
where security or backup policies must be set.Removable media storage devices can be used by other
machines on the network. This reduces the number of devices
throughout the network and provides a centralized location
to manage their security. It is often more convenient to
install software on multiple machines from a centralized
installation media.NFS consists of a server and one or more
clients. The client remotely accesses the data that is stored
on the server machine. In order for this to function properly,
a few processes have to be configured and running.These daemons must be running on the server:NFSserverfile serverUNIX clientsrpcbindmountdnfsdDaemonDescriptionnfsdThe NFS daemon which services
requests from NFS clients.mountdThe NFS mount daemon which
carries out requests received from
nfsd.rpcbind This daemon allows NFS
clients to discover which port the
NFS server is using.Running &man.nfsiod.8; on the client can improve
performance, but is not required.Configuring the ServerNFSconfigurationThe file systems which the NFS server
will share are specified in /etc/exports.
Each line in this file specifies a file system to be exported,
which clients have access to that file system, and any access
options. When adding entries to this file, each exported file
system, its properties, and allowed hosts must occur on a
single line. If no clients are listed in the entry, then any
client on the network can mount that file system.NFSexport examplesThe following /etc/exports entries
demonstrate how to export file systems. The examples can be
modified to match the file systems and client names on the
reader's network. There are many options that can be used in
this file, but only a few will be mentioned here. See
&man.exports.5; for the full list of options.This example shows how to export
/cdrom to three hosts named
alpha,
bravo, and
charlie:/cdrom -ro alphabravocharlieThe -ro flag makes the file system
read-only, preventing clients from making any changes to the
exported file system. This example assumes that the host
names are either in DNS or in
/etc/hosts. Refer to &man.hosts.5; if
the network does not have a DNS
server.The next example exports /home to
three clients by IP address. This can be
useful for networks without DNS or
/etc/hosts entries. The
-alldirs flag allows subdirectories to be
mount points. In other words, it will not automatically mount
the subdirectories, but will permit the client to mount the
directories that are required as needed./home -alldirs 10.0.0.2 10.0.0.3 10.0.0.4This next example exports /a so that
two clients from different domains may access that file
system. The allows root on the remote system to
write data on the exported file system as root. If
-maproot=root is not specified, the
client's root user
will be mapped to the server's nobody account and will be
subject to the access limitations defined for nobody./a -maproot=root host.example.com box.example.orgA client can only be specified once per file system. For
example, if /usr is a single file system,
these entries would be invalid as both entries specify the
same host:# Invalid when /usr is one file system
/usr/src client
/usr/ports clientThe correct format for this situation is to use one
entry:/usr/src /usr/ports clientThe following is an example of a valid export list, where
/usr and /exports
are local file systems:# Export src and ports to client01 and client02, but only
# client01 has root privileges on it
/usr/src /usr/ports -maproot=root client01
/usr/src /usr/ports client02
# The client machines have root and can mount anywhere
# on /exports. Anyone in the world can mount /exports/obj read-only
/exports -alldirs -maproot=root client01 client02
/exports/obj -roTo enable the processes required by the
NFS server at boot time, add these options
to /etc/rc.conf:rpcbind_enable="YES"
nfs_server_enable="YES"
mountd_flags="-r"The server can be started now by running this
command:&prompt.root; service nfsd startWhenever the NFS server is started,
mountd also starts automatically.
However, mountd only reads
/etc/exports when it is started. To make
subsequent /etc/exports edits take effect
immediately, force mountd to reread
it:&prompt.root; service mountd reloadConfiguring the ClientTo enable NFS clients, set this option
in each client's /etc/rc.conf:nfs_client_enable="YES"Then, run this command on each NFS
client:&prompt.root; service nfsclient startThe client now has everything it needs to mount a remote
file system. In these examples, the server's name is
server and the client's name is
client. To mount
/home on
server to the
/mnt mount point on
client:NFSmounting&prompt.root; mount server:/home /mntThe files and directories in
/home will now be available on
client, in the
/mnt directory.To mount a remote file system each time the client boots,
add it to /etc/fstab:server:/home /mnt nfs rw 0 0Refer to &man.fstab.5; for a description of all available
options.LockingSome applications require file locking to operate
correctly. To enable locking, add these lines to
/etc/rc.conf on both the client and
server:rpc_lockd_enable="YES"
rpc_statd_enable="YES"Then start the applications:&prompt.root; service lockd start
&prompt.root; service statd startIf locking is not required on the server, the
NFS client can be configured to lock
locally by including when running
mount. Refer to &man.mount.nfs.8;
for further details.Automating Mounts with &man.amd.8;WylieStilwellContributed by ChernLeeRewritten by amdautomatic mounter daemonThe automatic mounter daemon,
amd, automatically mounts a remote
file system whenever a file or directory within that file
system is accessed. File systems that are inactive for a
period of time will be automatically unmounted by
amd.This daemon provides an alternative to modifying
/etc/fstab to list every client. It
operates by attaching itself as an NFS
server to the /host and
/net directories. When a file is
accessed within one of these directories,
amd looks up the corresponding
remote mount and automatically mounts it.
/net is used to mount an exported file
system from an IP address while
/host is used to mount an export from a
remote hostname. For instance, an attempt to access a file
within /host/foobar/usr would tell
amd to mount the
/usr export on the host
foobar.Mounting an Export with
amdIn this example, showmount -e shows
the exported file systems that can be mounted from the
NFS server,
foobar:&prompt.user; showmount -e foobar
Exports list on foobar:
/usr 10.10.10.0
/a 10.10.10.0
&prompt.user; cd /host/foobar/usrThe output from showmount shows
/usr as an export. When changing
directories to /host/foobar/usr,
amd intercepts the request and
attempts to resolve the hostname
foobar. If successful,
amd automatically mounts the
desired export.To enable amd at boot time, add
this line to /etc/rc.conf:amd_enable="YES"To start amd now:&prompt.root; service amd startCustom flags can be passed to
amd from the
amd_flags environment variable. By
default, amd_flags is set to:amd_flags="-a /.amd_mnt -l syslog /host /etc/amd.map /net /etc/amd.map"The default options with which exports are mounted are
defined in /etc/amd.map. Some of the
more advanced features of amd are
defined in /etc/amd.conf.Consult &man.amd.8; and &man.amd.conf.5; for more
information.Automating Mounts with &man.autofs.5;The &man.autofs.5; automount facility is supported
starting with &os; 10.1-RELEASE. To use the
automounter functionality in older versions of &os;, use
&man.amd.8; instead. This chapter only describes the
&man.autofs.5; automounter.autofsautomounter subsystemThe &man.autofs.5; facility is a common name for several
components that, together, allow for automatic mounting of
remote and local filesystems whenever a file or directory
within that file system is accessed. It consists of the
kernel component, &man.autofs.5;, and several userspace
applications: &man.automount.8;, &man.automountd.8; and
&man.autounmountd.8;. It serves as an alternative for
&man.amd.8; from previous &os; releases. Amd is still
provided for backward compatibility purposes, as the two use
different map format; the one used by autofs is the same as
with other SVR4 automounters, such as the ones in Solaris,
MacOS X, and Linux.The &man.autofs.5; virtual filesystem is mounted on
specified mountpoints by &man.automount.8;, usually invoked
during boot.Whenever a process attempts to access file within the
&man.autofs.5; mountpoint, the kernel will notify
&man.automountd.8; daemon and pause the triggering process.
The &man.automountd.8; daemon will handle kernel requests by
finding the proper map and mounting the filesystem according
to it, then signal the kernel to release blocked process. The
&man.autounmountd.8; daemon automatically unmounts automounted
filesystems after some time, unless they are still being
used.The primary autofs configuration file is
/etc/auto_master. It assigns individual
maps to top-level mounts. For an explanation of
auto_master and the map syntax, refer to
&man.auto.master.5;.There is a special automounter map mounted on
/net. When a file is accessed within
this directory, &man.autofs.5; looks up the corresponding
remote mount and automatically mounts it. For instance, an
attempt to access a file within
/net/foobar/usr would tell
&man.automountd.8; to mount the /usr export from the host
foobar.Mounting an Export with &man.autofs.5;In this example, showmount -e shows
the exported file systems that can be mounted from the
NFS server,
foobar:&prompt.user; showmount -e foobar
Exports list on foobar:
/usr 10.10.10.0
/a 10.10.10.0
&prompt.user; cd /net/foobar/usrThe output from showmount shows
/usr as an export.
When changing directories to /host/foobar/usr,
&man.automountd.8; intercepts the request and attempts to
resolve the hostname foobar. If successful,
&man.automountd.8; automatically mounts the source
export.To enable &man.autofs.5; at boot time, add this line to
/etc/rc.conf:autofs_enable="YES"Then &man.autofs.5; can be started by running:&prompt.root; service automount start
&prompt.root; service automountd start
&prompt.root; service autounmountd startThe &man.autofs.5; map format is the same as in other
operating systems, it might be desirable to consult
information from other operating systems, such as the Mac
OS X document.Consult the &man.automount.8;, &man.automountd.8;,
&man.autounmountd.8;, and &man.auto.master.5; manual pages for
more information.Network Information System
(NIS)NISSolarisHP-UXAIXLinuxNetBSDOpenBSDyellow pagesNISNetwork Information System (NIS) is
designed to centralize administration of &unix;-like systems
such as &solaris;, HP-UX, &aix;, Linux, NetBSD, OpenBSD, and
&os;. NIS was originally known as Yellow
Pages but the name was changed due to trademark issues. This
is the reason why NIS commands begin with
yp.NISdomainsNIS is a Remote Procedure Call
(RPC)-based client/server system that allows
a group of machines within an NIS domain to
share a common set of configuration files. This permits a
system administrator to set up NIS client
systems with only minimal configuration data and to add, remove,
or modify configuration data from a single location.&os; uses version 2 of the NIS
protocol.NIS Terms and ProcessesTable 28.1 summarizes the terms and important processes
used by NIS:rpcbindportmap
NIS TerminologyTermDescriptionNIS domain nameNIS servers and clients share
an NIS domain name. Typically,
this name does not have anything to do with
DNS.&man.rpcbind.8;This service enables RPC and
must be running in order to run an
NIS server or act as an
NIS client.&man.ypbind.8;This service binds an NIS
client to its NIS server. It will
take the NIS domain name and use
RPC to connect to the server. It
is the core of client/server communication in an
NIS environment. If this service
is not running on a client machine, it will not be
able to access the NIS
server.&man.ypserv.8;This is the process for the
NIS server. If this service stops
running, the server will no longer be able to respond
to NIS requests so hopefully, there
is a slave server to take over. Some non-&os; clients
will not try to reconnect using a slave server and the
ypbind process may need to
be restarted on these
clients.&man.rpc.yppasswdd.8;This process only runs on
NIS master servers. This daemon
allows NIS clients to change their
NIS passwords. If this daemon is
not running, users will have to login to the
NIS master server and change their
passwords there.
Machine TypesNISmaster serverNISslave serverNISclientThere are three types of hosts in an
NIS environment:NIS master serverThis server acts as a central repository for host
configuration information and maintains the
authoritative copy of the files used by all of the
NIS clients. The
passwd, group,
and other various files used by NIS
clients are stored on the master server. While it is
possible for one machine to be an NIS
master server for more than one NIS
domain, this type of configuration will not be covered in
this chapter as it assumes a relatively small-scale
NIS environment.NIS slave serversNIS slave servers maintain copies
of the NIS master's data files in
order to provide redundancy. Slave servers also help to
balance the load of the master server as
NIS clients always attach to the
NIS server which responds
first.NIS clientsNIS clients authenticate
against the NIS server during log
on.Information in many files can be shared using
NIS. The
master.passwd,
group, and hosts
files are commonly shared via NIS.
Whenever a process on a client needs information that would
normally be found in these files locally, it makes a query to
the NIS server that it is bound to
instead.Planning ConsiderationsThis section describes a sample NIS
environment which consists of 15 &os; machines with no
centralized point of administration. Each machine has its own
/etc/passwd and
/etc/master.passwd. These files are kept
in sync with each other only through manual intervention.
Currently, when a user is added to the lab, the process must
be repeated on all 15 machines.The configuration of the lab will be as follows:Machine nameIP addressMachine roleellington10.0.0.2NIS mastercoltrane10.0.0.3NIS slavebasie10.0.0.4Faculty workstationbird10.0.0.5Client machinecli[1-11]10.0.0.[6-17]Other client machinesIf this is the first time an NIS
scheme is being developed, it should be thoroughly planned
ahead of time. Regardless of network size, several decisions
need to be made as part of the planning process.Choosing a NIS Domain NameNISdomain nameWhen a client broadcasts its requests for info, it
includes the name of the NIS domain that
it is part of. This is how multiple servers on one network
can tell which server should answer which request. Think of
the NIS domain name as the name for a
group of hosts.Some organizations choose to use their Internet domain
name for their NIS domain name. This is
not recommended as it can cause confusion when trying to
debug network problems. The NIS domain
name should be unique within the network and it is helpful
if it describes the group of machines it represents. For
example, the Art department at Acme Inc. might be in the
acme-art NIS domain. This
example will use the domain name
test-domain.However, some non-&os; operating systems require the
NIS domain name to be the same as the
Internet domain name. If one or more machines on the
network have this restriction, the Internet domain name
must be used as the
NIS domain name.Physical Server RequirementsThere are several things to keep in mind when choosing a
machine to use as a NIS server. Since
NIS clients depend upon the availability
of the server, choose a machine that is not rebooted
frequently. The NIS server should
ideally be a stand alone machine whose sole purpose is to be
an NIS server. If the network is not
heavily used, it is acceptable to put the
NIS server on a machine running other
services. However, if the NIS server
becomes unavailable, it will adversely affect all
NIS clients.Configuring the NIS Master
Server The canonical copies of all NIS files
are stored on the master server. The databases used to store
the information are called NIS maps. In
&os;, these maps are stored in
/var/yp/[domainname] where
[domainname] is the name of the
NIS domain. Since multiple domains are
supported, it is possible to have several directories, one for
each domain. Each domain will have its own independent set of
maps.NIS master and slave servers handle all
NIS requests through &man.ypserv.8;. This
daemon is responsible for receiving incoming requests from
NIS clients, translating the requested
domain and map name to a path to the corresponding database
file, and transmitting data from the database back to the
client.NISserver configurationSetting up a master NIS server can be
relatively straight forward, depending on environmental needs.
Since &os; provides built-in NIS support,
it only needs to be enabled by adding the following lines to
/etc/rc.conf:nisdomainname="test-domain"
nis_server_enable="YES"
nis_yppasswdd_enable="YES" This line sets the NIS domain name
to test-domain.This automates the start up of the
NIS server processes when the system
boots.This enables the &man.rpc.yppasswdd.8; daemon so that
users can change their NIS password
from a client machine.Care must be taken in a multi-server domain where the
server machines are also NIS clients. It
is generally a good idea to force the servers to bind to
themselves rather than allowing them to broadcast bind
requests and possibly become bound to each other. Strange
failure modes can result if one server goes down and others
are dependent upon it. Eventually, all the clients will time
out and attempt to bind to other servers, but the delay
involved can be considerable and the failure mode is still
present since the servers might bind to each other all over
again.A server that is also a client can be forced to bind to a
particular server by adding these additional lines to
/etc/rc.conf:nis_client_enable="YES" # run client stuff as well
nis_client_flags="-S NIS domain,server"After saving the edits, type
/etc/netstart to restart the network and
apply the values defined in /etc/rc.conf.
Before initializing the NIS maps, start
&man.ypserv.8;:&prompt.root; service ypserv startInitializing the NIS MapsNISmapsNIS maps are generated from the
configuration files in /etc on the
NIS master, with one exception:
/etc/master.passwd. This is to prevent
the propagation of passwords to all the servers in the
NIS domain. Therefore, before the
NIS maps are initialized, configure the
primary password files:&prompt.root; cp /etc/master.passwd /var/yp/master.passwd
&prompt.root; cd /var/yp
&prompt.root; vi master.passwdIt is advisable to remove all entries for system
accounts as well as any user accounts that do not need to be
propagated to the NIS clients, such as
the root and any
other administrative accounts.Ensure that the
/var/yp/master.passwd is neither group
or world readable by setting its permissions to
600.After completing this task, initialize the
NIS maps. &os; includes the
&man.ypinit.8; script to do this. When generating maps
for the master server, include and
specify the NIS domain name:ellington&prompt.root; ypinit -m test-domain
Server Type: MASTER Domain: test-domain
Creating an YP server will require that you answer a few questions.
Questions will all be asked at the beginning of the procedure.
Do you want this procedure to quit on non-fatal errors? [y/n: n] n
Ok, please remember to go back and redo manually whatever fails.
If not, something might not work.
At this point, we have to construct a list of this domains YP servers.
rod.darktech.org is already known as master server.
Please continue to add any slave servers, one per line. When you are
done with the list, type a <control D>.
master server : ellington
next host to add: coltrane
next host to add: ^D
The current list of NIS servers looks like this:
ellington
coltrane
Is this correct? [y/n: y] y
[..output from map generation..]
NIS Map update completed.
ellington has been setup as an YP master server without any errors.This will create /var/yp/Makefile
from /var/yp/Makefile.dist. By
default, this file assumes that the environment has a
single NIS server with only &os; clients.
Since test-domain has a slave server,
edit this line in /var/yp/Makefile so
that it begins with a comment
(#):NOPUSH = "True"Adding New UsersEvery time a new user is created, the user account must
be added to the master NIS server and the
NIS maps rebuilt. Until this occurs, the
new user will not be able to login anywhere except on the
NIS master. For example, to add the new
user jsmith to the
test-domain domain, run these commands on
the master server:&prompt.root; pw useradd jsmith
&prompt.root; cd /var/yp
&prompt.root; make test-domainThe user could also be added using adduser
jsmith instead of pw useradd
smith.Setting up a NIS Slave ServerNISslave serverTo set up an NIS slave server, log on
to the slave server and edit /etc/rc.conf
as for the master server. Do not generate any
NIS maps, as these already exist on the
master server. When running ypinit on the
slave server, use (for slave) instead of
(for master). This option requires the
name of the NIS master in addition to the
domain name, as seen in this example:coltrane&prompt.root; ypinit -s ellington test-domain
Server Type: SLAVE Domain: test-domain Master: ellington
Creating an YP server will require that you answer a few questions.
Questions will all be asked at the beginning of the procedure.
Do you want this procedure to quit on non-fatal errors? [y/n: n] n
Ok, please remember to go back and redo manually whatever fails.
If not, something might not work.
There will be no further questions. The remainder of the procedure
should take a few minutes, to copy the databases from ellington.
Transferring netgroup...
ypxfr: Exiting: Map successfully transferred
Transferring netgroup.byuser...
ypxfr: Exiting: Map successfully transferred
Transferring netgroup.byhost...
ypxfr: Exiting: Map successfully transferred
Transferring master.passwd.byuid...
ypxfr: Exiting: Map successfully transferred
Transferring passwd.byuid...
ypxfr: Exiting: Map successfully transferred
Transferring passwd.byname...
ypxfr: Exiting: Map successfully transferred
Transferring group.bygid...
ypxfr: Exiting: Map successfully transferred
Transferring group.byname...
ypxfr: Exiting: Map successfully transferred
Transferring services.byname...
ypxfr: Exiting: Map successfully transferred
Transferring rpc.bynumber...
ypxfr: Exiting: Map successfully transferred
Transferring rpc.byname...
ypxfr: Exiting: Map successfully transferred
Transferring protocols.byname...
ypxfr: Exiting: Map successfully transferred
Transferring master.passwd.byname...
ypxfr: Exiting: Map successfully transferred
Transferring networks.byname...
ypxfr: Exiting: Map successfully transferred
Transferring networks.byaddr...
ypxfr: Exiting: Map successfully transferred
Transferring netid.byname...
ypxfr: Exiting: Map successfully transferred
Transferring hosts.byaddr...
ypxfr: Exiting: Map successfully transferred
Transferring protocols.bynumber...
ypxfr: Exiting: Map successfully transferred
Transferring ypservers...
ypxfr: Exiting: Map successfully transferred
Transferring hosts.byname...
ypxfr: Exiting: Map successfully transferred
coltrane has been setup as an YP slave server without any errors.
Remember to update map ypservers on ellington.This will generate a directory on the slave server called
/var/yp/test-domain which contains copies
of the NIS master server's maps. Adding
these /etc/crontab entries on each slave
server will force the slaves to sync their maps with the maps
on the master server:20 * * * * root /usr/libexec/ypxfr passwd.byname
21 * * * * root /usr/libexec/ypxfr passwd.byuidThese entries are not mandatory because the master server
automatically attempts to push any map changes to its slaves.
However, since clients may depend upon the slave server to
provide correct password information, it is recommended to
force frequent password map updates. This is especially
important on busy networks where map updates might not always
complete.To finish the configuration, run
/etc/netstart on the slave server in order
to start the NIS services.Setting Up an NIS ClientAn NIS client binds to an
NIS server using &man.ypbind.8;. This
daemon broadcasts RPC requests on the local network. These
requests specify the domain name configured on the client. If
an NIS server in the same domain receives
one of the broadcasts, it will respond to
ypbind, which will record the
server's address. If there are several servers available,
the client will use the address of the first server to respond
and will direct all of its NIS requests to
that server. The client will automatically
ping the server on a regular basis
to make sure it is still available. If it fails to receive a
reply within a reasonable amount of time,
ypbind will mark the domain as
unbound and begin broadcasting again in the hopes of locating
another server.NISclient configurationTo configure a &os; machine to be an
NIS client:Edit /etc/rc.conf and add the
following lines in order to set the
NIS domain name and start
&man.ypbind.8; during network startup:nisdomainname="test-domain"
nis_client_enable="YES"To import all possible password entries from the
NIS server, use
vipw to remove all user accounts
except one from /etc/master.passwd.
When removing the accounts, keep in mind that at least one
local account should remain and this account should be a
member of wheel. If there is a
problem with NIS, this local account
can be used to log in remotely, become the superuser, and
fix the problem. Before saving the edits, add the
following line to the end of the file:+:::::::::This line configures the client to provide anyone with
a valid account in the NIS server's
password maps an account on the client. There are many
ways to configure the NIS client by
modifying this line. One method is described in . For more detailed
reading, refer to the book
Managing NFS and NIS, published by
O'Reilly Media.To import all possible group entries from the
NIS server, add this line to
/etc/group:+:*::To start the NIS client immediately,
execute the following commands as the superuser:&prompt.root; /etc/netstart
&prompt.root; service ypbind startAfter completing these steps, running
ypcat passwd on the client should show
the server's passwd map.NIS SecuritySince RPC is a broadcast-based service,
any system running ypbind within
the same domain can retrieve the contents of the
NIS maps. To prevent unauthorized
transactions, &man.ypserv.8; supports a feature called
securenets which can be used to restrict access
to a given set of hosts. By default, this information is
stored in /var/yp/securenets, unless
&man.ypserv.8; is started with and an
alternate path. This file contains entries that consist of a
network specification and a network mask separated by white
space. Lines starting with # are
considered to be comments. A sample
securenets might look like this:# allow connections from local host -- mandatory
127.0.0.1 255.255.255.255
# allow connections from any host
# on the 192.168.128.0 network
192.168.128.0 255.255.255.0
# allow connections from any host
# between 10.0.0.0 to 10.0.15.255
# this includes the machines in the testlab
10.0.0.0 255.255.240.0If &man.ypserv.8; receives a request from an address that
matches one of these rules, it will process the request
normally. If the address fails to match a rule, the request
will be ignored and a warning message will be logged. If the
securenets does not exist,
ypserv will allow connections from any
host. is an alternate mechanism
for providing access control instead of
securenets. While either access control
mechanism adds some security, they are both vulnerable to
IP spoofing attacks. All
NIS-related traffic should be blocked at
the firewall.Servers using securenets
may fail to serve legitimate NIS clients
with archaic TCP/IP implementations. Some of these
implementations set all host bits to zero when doing
broadcasts or fail to observe the subnet mask when
calculating the broadcast address. While some of these
problems can be fixed by changing the client configuration,
other problems may force the retirement of these client
systems or the abandonment of
securenets.TCP WrapperThe use of TCP Wrapper
increases the latency of the NIS server.
The additional delay may be long enough to cause timeouts in
client programs, especially in busy networks with slow
NIS servers. If one or more clients suffer
from latency, convert those clients into
NIS slave servers and force them to bind to
themselves.Barring Some UsersIn this example, the basie
system is a faculty workstation within the
NIS domain. The
passwd map on the master
NIS server contains accounts for both
faculty and students. This section demonstrates how to
allow faculty logins on this system while refusing student
logins.To prevent specified users from logging on to a system,
even if they are present in the NIS
database, use vipw to add
-username with
the correct number of colons towards the end of
/etc/master.passwd on the client,
where username is the username of
a user to bar from logging in. The line with the blocked
user must be before the + line that
allows NIS users. In this example,
bill is barred
from logging on to basie:basie&prompt.root; cat /etc/master.passwd
root:[password]:0:0::0:0:The super-user:/root:/bin/csh
toor:[password]:0:0::0:0:The other super-user:/root:/bin/sh
daemon:*:1:1::0:0:Owner of many system processes:/root:/sbin/nologin
operator:*:2:5::0:0:System &:/:/sbin/nologin
bin:*:3:7::0:0:Binaries Commands and Source,,,:/:/sbin/nologin
tty:*:4:65533::0:0:Tty Sandbox:/:/sbin/nologin
kmem:*:5:65533::0:0:KMem Sandbox:/:/sbin/nologin
games:*:7:13::0:0:Games pseudo-user:/usr/games:/sbin/nologin
news:*:8:8::0:0:News Subsystem:/:/sbin/nologin
man:*:9:9::0:0:Mister Man Pages:/usr/share/man:/sbin/nologin
bind:*:53:53::0:0:Bind Sandbox:/:/sbin/nologin
uucp:*:66:66::0:0:UUCP pseudo-user:/var/spool/uucppublic:/usr/libexec/uucp/uucico
xten:*:67:67::0:0:X-10 daemon:/usr/local/xten:/sbin/nologin
pop:*:68:6::0:0:Post Office Owner:/nonexistent:/sbin/nologin
nobody:*:65534:65534::0:0:Unprivileged user:/nonexistent:/sbin/nologin
-bill:::::::::
+:::::::::
basie&prompt.root;Using NetgroupsnetgroupsBarring specified users from logging on to individual
systems becomes unscaleable on larger networks and quickly
loses the main benefit of NIS:
centralized administration.Netgroups were developed to handle large, complex networks
with hundreds of users and machines. Their use is comparable
to &unix; groups, where the main difference is the lack of a
numeric ID and the ability to define a netgroup by including
both user accounts and other netgroups.To expand on the example used in this chapter, the
NIS domain will be extended to add the
users and systems shown in Tables 28.2 and 28.3:
Additional UsersUser Name(s)Descriptionalpha,
betaIT department employeescharlie, deltaIT department apprenticesecho,
foxtrott,
golf,
...employeesable,
baker,
...interns
Additional SystemsMachine Name(s)Descriptionwar,
death,
famine,
pollutionOnly IT employees are allowed to log onto these
servers.pride,
greed,
envy,
wrath,
lust,
slothAll members of the IT department are allowed to
login onto these servers.one,
two,
three,
four,
...Ordinary workstations used by
employees.trashcanA very old machine without any critical data.
Even interns are allowed to use this system.
When using netgroups to configure this scenario, each user
is assigned to one or more netgroups and logins are then
allowed or forbidden for all members of the netgroup. When
adding a new machine, login restrictions must be defined for
all netgroups. When a new user is added, the account must be
added to one or more netgroups. If the
NIS setup is planned carefully, only one
central configuration file needs modification to grant or deny
access to machines.The first step is the initialization of the
NIS netgroup map. In
&os;, this map is not created by default. On the
NIS master server, use an editor to create
a map named /var/yp/netgroup.This example creates four netgroups to represent IT
employees, IT apprentices, employees, and interns:IT_EMP (,alpha,test-domain) (,beta,test-domain)
IT_APP (,charlie,test-domain) (,delta,test-domain)
USERS (,echo,test-domain) (,foxtrott,test-domain) \
(,golf,test-domain)
INTERNS (,able,test-domain) (,baker,test-domain)Each entry configures a netgroup. The first column in an
entry is the name of the netgroup. Each set of brackets
represents either a group of one or more users or the name of
another netgroup. When specifying a user, the three
comma-delimited fields inside each group represent:The name of the host(s) where the other fields
representing the user are valid. If a hostname is not
specified, the entry is valid on all hosts.The name of the account that belongs to this
netgroup.The NIS domain for the account.
Accounts may be imported from other NIS
domains into a netgroup.If a group contains multiple users, separate each user
with whitespace. Additionally, each field may contain
wildcards. See &man.netgroup.5; for details.netgroupsNetgroup names longer than 8 characters should not be
used. The names are case sensitive and using capital letters
for netgroup names is an easy way to distinguish between user,
machine and netgroup names.Some non-&os; NIS clients cannot
handle netgroups containing more than 15 entries. This
limit may be circumvented by creating several sub-netgroups
with 15 users or fewer and a real netgroup consisting of the
sub-netgroups, as seen in this example:BIGGRP1 (,joe1,domain) (,joe2,domain) (,joe3,domain) [...]
BIGGRP2 (,joe16,domain) (,joe17,domain) [...]
BIGGRP3 (,joe31,domain) (,joe32,domain)
BIGGROUP BIGGRP1 BIGGRP2 BIGGRP3Repeat this process if more than 225 (15 times 15) users
exist within a single netgroup.To activate and distribute the new
NIS map:ellington&prompt.root; cd /var/yp
ellington&prompt.root; makeThis will generate the three NIS maps
netgroup,
netgroup.byhost and
netgroup.byuser. Use the map key option
of &man.ypcat.1; to check if the new NIS
maps are available:ellington&prompt.user; ypcat -k netgroup
ellington&prompt.user; ypcat -k netgroup.byhost
ellington&prompt.user; ypcat -k netgroup.byuserThe output of the first command should resemble the
contents of /var/yp/netgroup. The second
command only produces output if host-specific netgroups were
created. The third command is used to get the list of
netgroups for a user.To configure a client, use &man.vipw.8; to specify the
name of the netgroup. For example, on the server named
war, replace this line:+:::::::::with+@IT_EMP:::::::::This specifies that only the users defined in the netgroup
IT_EMP will be imported into this system's
password database and only those users are allowed to login to
this system.This configuration also applies to the
~ function of the shell and all routines
which convert between user names and numerical user IDs. In
other words,
cd ~user will
not work, ls -l will show the numerical ID
instead of the username, and find . -user joe
-print will fail with the message
No such user. To fix this, import all
user entries without allowing them to login into the servers.
This can be achieved by adding an extra line:+:::::::::/sbin/nologinThis line configures the client to import all entries but
to replace the shell in those entries with
/sbin/nologin.Make sure that extra line is placed
after+@IT_EMP:::::::::. Otherwise, all user
accounts imported from NIS will have
/sbin/nologin as their login
shell and no one will be able to login to the system.To configure the less important servers, replace the old
+::::::::: on the servers with these
lines:+@IT_EMP:::::::::
+@IT_APP:::::::::
+:::::::::/sbin/nologinThe corresponding lines for the workstations
would be:+@IT_EMP:::::::::
+@USERS:::::::::
+:::::::::/sbin/nologinNIS supports the creation of netgroups from other
netgroups which can be useful if the policy regarding user
access changes. One possibility is the creation of role-based
netgroups. For example, one might create a netgroup called
BIGSRV to define the login restrictions for
the important servers, another netgroup called
SMALLSRV for the less important servers,
and a third netgroup called USERBOX for the
workstations. Each of these netgroups contains the netgroups
that are allowed to login onto these machines. The new
entries for the NIS
netgroup map would look like this:BIGSRV IT_EMP IT_APP
SMALLSRV IT_EMP IT_APP ITINTERN
USERBOX IT_EMP ITINTERN USERSThis method of defining login restrictions works
reasonably well when it is possible to define groups of
machines with identical restrictions. Unfortunately, this is
the exception and not the rule. Most of the time, the ability
to define login restrictions on a per-machine basis is
required.Machine-specific netgroup definitions are another
possibility to deal with the policy changes. In this
scenario, the /etc/master.passwd of each
system contains two lines starting with +.
The first line adds a netgroup with the accounts allowed to
login onto this machine and the second line adds all other
accounts with /sbin/nologin as shell. It
is recommended to use the ALL-CAPS version of
the hostname as the name of the netgroup:+@BOXNAME:::::::::
+:::::::::/sbin/nologinOnce this task is completed on all the machines, there is
no longer a need to modify the local versions of
/etc/master.passwd ever again. All
further changes can be handled by modifying the
NIS map. Here is an example of a possible
netgroup map for this scenario:# Define groups of users first
IT_EMP (,alpha,test-domain) (,beta,test-domain)
IT_APP (,charlie,test-domain) (,delta,test-domain)
DEPT1 (,echo,test-domain) (,foxtrott,test-domain)
DEPT2 (,golf,test-domain) (,hotel,test-domain)
DEPT3 (,india,test-domain) (,juliet,test-domain)
ITINTERN (,kilo,test-domain) (,lima,test-domain)
D_INTERNS (,able,test-domain) (,baker,test-domain)
#
# Now, define some groups based on roles
USERS DEPT1 DEPT2 DEPT3
BIGSRV IT_EMP IT_APP
SMALLSRV IT_EMP IT_APP ITINTERN
USERBOX IT_EMP ITINTERN USERS
#
# And a groups for a special tasks
# Allow echo and golf to access our anti-virus-machine
SECURITY IT_EMP (,echo,test-domain) (,golf,test-domain)
#
# machine-based netgroups
# Our main servers
WAR BIGSRV
FAMINE BIGSRV
# User india needs access to this server
POLLUTION BIGSRV (,india,test-domain)
#
# This one is really important and needs more access restrictions
DEATH IT_EMP
#
# The anti-virus-machine mentioned above
ONE SECURITY
#
# Restrict a machine to a single user
TWO (,hotel,test-domain)
# [...more groups to follow]It may not always be advisable
to use machine-based netgroups. When deploying a couple of
dozen or hundreds of systems,
role-based netgroups instead of machine-based netgroups may be
used to keep the size of the NIS map within
reasonable limits.Password FormatsNISpassword formatsNIS requires that all hosts within an
NIS domain use the same format for
encrypting passwords. If users have trouble authenticating on
an NIS client, it may be due to a differing
password format. In a heterogeneous network, the format must
be supported by all operating systems, where
DES is the lowest common standard.To check which format a server or client is using, look
at this section of
/etc/login.conf:default:\
:passwd_format=des:\
:copyright=/etc/COPYRIGHT:\
[Further entries elided]In this example, the system is using the
DES format. Other possible values are
blf for Blowfish and md5
for MD5 encrypted passwords.If the format on a host needs to be edited to match the
one being used in the NIS domain, the
login capability database must be rebuilt after saving the
change:&prompt.root; cap_mkdb /etc/login.confThe format of passwords for existing user accounts will
not be updated until each user changes their password
after the login capability database is
rebuilt.Lightweight Directory Access Protocol
(LDAP)TomRhodesWritten by LDAPThe Lightweight Directory Access Protocol
(LDAP) is an application layer protocol used
to access, modify, and authenticate objects using a distributed
directory information service. Think of it as a phone or record
book which stores several levels of hierarchical, homogeneous
information. It is used in Active Directory and
OpenLDAP networks and allows users to
access to several levels of internal information utilizing a
single account. For example, email authentication, pulling
employee contact information, and internal website
authentication might all make use of a single user account in
the LDAP server's record base.This section provides a quick start guide for configuring an
LDAP server on a &os; system. It assumes
that the administrator already has a design plan which includes
the type of information to store, what that information will be
used for, which users should have access to that information,
and how to secure this information from unauthorized
access.LDAP Terminology and StructureLDAP uses several terms which should be
understood before starting the configuration. All directory
entries consist of a group of
attributes. Each of these attribute
sets contains a unique identifier known as a
Distinguished Name
(DN) which is normally built from several
other attributes such as the common or
Relative Distinguished Name
(RDN). Similar to how directories have
absolute and relative paths, consider a DN
as an absolute path and the RDN as the
relative path.An example LDAP entry looks like the
following. This example searches for the entry for the
specified user account (uid),
organizational unit (ou), and organization
(o):&prompt.user; ldapsearch -xb "uid=trhodes,ou=users,o=example.com"
# extended LDIF
#
# LDAPv3
# base <uid=trhodes,ou=users,o=example.com> with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#
# trhodes, users, example.com
dn: uid=trhodes,ou=users,o=example.com
mail: trhodes@example.com
cn: Tom Rhodes
uid: trhodes
telephoneNumber: (123) 456-7890
# search result
search: 2
result: 0 Success
# numResponses: 2
# numEntries: 1This example entry shows the values for the
dn, mail,
cn, uid, and
telephoneNumber attributes. The
cn attribute is the
RDN.More information about LDAP and its
terminology can be found at http://www.openldap.org/doc/admin24/intro.html.Configuring an LDAP ServerLDAP Server&os; does not provide a built-in LDAP
server. Begin the configuration by installing the net/openldap24-server package or port.
Since the port has many configurable options, it is
recommended that the default options are reviewed to see if
the package is sufficient, and to instead compile the port if
any options should be changed. In most cases, the defaults
are fine. However, if SQL support is needed, this option must
be enabled and the port compiled using the instructions in
.Next, create the directories to hold the data and to store
the certificates:&prompt.root; mkdir /var/db/openldap-data
&prompt.root; mkdir /usr/local/etc/openldap/privateCopy over the database configuration file:&prompt.root; cp /usr/local/etc/openldap/DB_CONFIG.example /var/db/openldap-data/DB_CONFIGThe next phase is to configure the certificate authority.
The following commands must be executed from
/usr/local/etc/openldap/private. This is
important as the file permissions need to be restrictive and
users should not have access to these files. To create the
certificate authority, start with this command and follow the
prompts:&prompt.root; openssl req -days 365 -nodes -new -x509 -keyout ca.key -out ../ca.crtThe entries for the prompts may be generic
except for the
Common Name. This entry must be
different than the system hostname. If
this will be a self signed certificate, prefix the hostname
with CA for certificate authority.The next task is to create a certificate signing request
and a private key. Input this command and follow the
prompts:&prompt.root; openssl req -days 365 -nodes -new -keyout server.key -out server.csrDuring the certificate generation process, be sure to
correctly set the Common Name attribute.
Once complete, sign the key:&prompt.root; openssl x509 -req -days 365 -in server.csr -out ../server.crt -CA ../ca.crt -CAkey ca.key -CAcreateserialThe final part of the certificate generation process is to
generate and sign the client certificates:&prompt.root; openssl req -days 365 -nodes -new -keyout client.key -out client.csr
&prompt.root; openssl x509 -req -days 3650 -in client.csr -out ../client.crt -CA ../ca.crt -CAkey ca.keyRemember to use the same Common Name
attribute when prompted. When finished, ensure that a total
of eight (8) new files have been generated through the
proceeding commands. If so, the next step is to edit
/usr/local/etc/openldap/slapd.conf and
add the following options:TLSCipherSuite HIGH:MEDIUM:+SSLv3
TLSCertificateFile /usr/local/etc/openldap/server.crt
TLSCertificateKeyFile /usr/local/etc/openldap/private/server.key
TLSCACertificateFile /usr/local/etc/openldap/ca.crtThen, edit
/usr/local/etc/openldap/ldap.conf and add
the following lines:TLS_CACERT /usr/local/etc/openldap/ca.crt
TLS_CIPHER_SUITE HIGH:MEDIUM:+SSLv3While editing this file, uncomment the following entries
and set them to the desired values: ,
, and
. Set the to
contain and
. Then, add two entries pointing to
the certificate authority. When finished, the entries should
look similar to the following:BASE dc=example,dc=com
URI ldap:// ldaps://
SIZELIMIT 12
TIMELIMIT 15
TLS_CACERT /usr/local/etc/openldap/ca.crt
TLS_CIPHER_SUITE HIGH:MEDIUM:+SSLv3The default password for the server should then be
changed:&prompt.root; slappasswd -h "{SHA}" >> /usr/local/etc/openldap/slapd.confThis command will prompt for the password and, if the
process does not fail, a password hash will be added to the
end of slapd.conf. Several hashing
formats are supported. Refer to the manual page for
slappasswd for more information.Next, edit
/usr/local/etc/openldap/slapd.conf and
add the following lines:password-hash {sha}
allow bind_v2The in this file must be updated
to match the used in
/usr/local/etc/openldap/ldap.conf and
should also be set. A recommended
value for is something like
. Before saving this file, place
the in front of the password output
from slappasswd and delete the old
. The end result should
look similar to this:TLSCipherSuite HIGH:MEDIUM:+SSLv3
TLSCertificateFile /usr/local/etc/openldap/server.crt
TLSCertificateKeyFile /usr/local/etc/openldap/private/server.key
TLSCACertificateFile /usr/local/etc/openldap/ca.crt
rootpw {SHA}W6ph5Mm5Pz8GgiULbPgzG37mj9g=Finally, enable the OpenLDAP
service in /etc/rc.conf and set the
URI:slapd_enable="YES"
slapd_flags="-4 -h ldaps:///"At this point the server can be started and tested:&prompt.root; service slapd startIf everything is configured correctly, a search of the
directory should show a successful connection with a single
response as in this example:&prompt.root; ldapsearch -Z
# extended LDIF
#
# LDAPv3
# base <dc=example,dc=com> (default) with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#
# search result
search: 3
result: 32 No such object
# numResponses: 1If the command fails and the configuration looks
correct, stop the slapd service and
restart it with debugging options:&prompt.root; service slapd stop
&prompt.root; /usr/local/libexec/slapd -d -1Once the service is responding, the directory can be
populated using ldapadd. In this example,
a file containing this list of users is first created. Each
user should use the following format:dn: dc=example,dc=com
objectclass: dcObject
objectclass: organization
o: Example
dc: Example
dn: cn=Manager,dc=example,dc=com
objectclass: organizationalRole
cn: ManagerTo import this file, specify the file name. The following
command will prompt for the password specified earlier and the
output should look something like this:&prompt.root; ldapadd -Z -D "cn=Manager,dc=example,dc=com" -W -f import.ldif
Enter LDAP Password:
adding new entry "dc=example,dc=com"
adding new entry "cn=Manager,dc=example,dc=com"Verify the data was added by issuing a search on the
server using ldapsearch:&prompt.user; ldapsearch -Z
# extended LDIF
#
# LDAPv3
# base <dc=example,dc=com> (default) with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#
# example.com
dn: dc=example,dc=com
objectClass: dcObject
objectClass: organization
o: Example
dc: Example
# Manager, example.com
dn: cn=Manager,dc=example,dc=com
objectClass: organizationalRole
cn: Manager
# search result
search: 3
result: 0 Success
# numResponses: 3
# numEntries: 2At this point, the server should be configured and
functioning properly.Dynamic Host Configuration Protocol
(DHCP)Dynamic Host Configuration ProtocolDHCPInternet Systems Consortium (ISC)The Dynamic Host Configuration Protocol
(DHCP) allows a system to connect to a
network in order to be assigned the necessary addressing
information for communication on that network. &os; includes
the OpenBSD version of dhclient which is used
by the client to obtain the addressing information. &os; does
not install a DHCP server, but several
servers are available in the &os; Ports Collection. The
DHCP protocol is fully described in RFC
2131.
Informational resources are also available at isc.org/downloads/dhcp/.This section describes how to use the built-in
DHCP client. It then describes how to
install and configure a DHCP server.In &os;, the &man.bpf.4; device is needed by both the
DHCP server and DHCP
client. This device is included in the
GENERIC kernel that is installed with
&os;. Users who prefer to create a custom kernel need to keep
this device if DHCP is used.It should be noted that bpf also
allows privileged users to run network packet sniffers on
that system.Configuring a DHCP ClientDHCP client support is included in the
&os; installer, making it easy to configure a newly installed
system to automatically receive its networking addressing
information from an existing DHCP server.
Refer to for examples of
network configuration.UDPWhen dhclient is executed on the client
machine, it begins broadcasting requests for configuration
information. By default, these requests use
UDP port 68. The server replies on
UDP port 67, giving the client an
IP address and other relevant network
information such as a subnet mask, default gateway, and
DNS server addresses. This information is
in the form of a DHCP
lease and is valid for a configurable time.
This allows stale IP addresses for clients
no longer connected to the network to automatically be reused.
DHCP clients can obtain a great deal of
information from the server. An exhaustive list may be found
in &man.dhcp-options.5;.By default, when a &os; system boots, its
DHCP client runs in the background, or
asynchronously. Other startup scripts
continue to run while the DHCP process
completes, which speeds up system startup.Background DHCP works well when the
DHCP server responds quickly to the
client's requests. However, DHCP may take
a long time to complete on some systems. If network services
attempt to run before DHCP has assigned the
network addressing information, they will fail. Using
DHCP in synchronous
mode prevents this problem as it pauses startup until the
DHCP configuration has completed.This line in /etc/rc.conf is used to
configure background or asynchronous mode:ifconfig_fxp0="DHCP"This line may already exist if the system was configured
to use DHCP during installation. Replace
the fxp0 shown in these examples
with the name of the interface to be dynamically configured,
as described in .To instead configure the system to use synchronous mode,
and to pause during startup while DHCP
completes, use
SYNCDHCP:ifconfig_fxp0="SYNCDHCP"Additional client options are available. Search for
dhclient in &man.rc.conf.5; for
details.DHCPconfiguration filesThe DHCP client uses the following
files:/etc/dhclient.confThe configuration file used by
dhclient. Typically, this file
contains only comments as the defaults are suitable for
most clients. This configuration file is described in
&man.dhclient.conf.5;./sbin/dhclientMore information about the command itself can
be found in &man.dhclient.8;./sbin/dhclient-scriptThe
&os;-specific DHCP client configuration
script. It is described in &man.dhclient-script.8;, but
should not need any user modification to function
properly./var/db/dhclient.leases.interfaceThe DHCP client keeps a database of
valid leases in this file, which is written as a log and
is described in &man.dhclient.leases.5;.Installing and Configuring a DHCP
ServerThis section demonstrates how to configure a &os; system
to act as a DHCP server using the Internet
Systems Consortium (ISC) implementation of
the DHCP server. This implementation and
its documentation can be installed using the
net/isc-dhcp42-server package or
port.DHCPserverDHCPinstallationThe installation of
net/isc-dhcp42-server installs a sample
configuration file. Copy
/usr/local/etc/dhcpd.conf.example to
/usr/local/etc/dhcpd.conf and make any
edits to this new file.DHCPdhcpd.confThe configuration file is comprised of declarations for
subnets and hosts which define the information that is
provided to DHCP clients. For example,
these lines configure the following:option domain-name "example.org";
option domain-name-servers ns1.example.org;
option subnet-mask 255.255.255.0;
default-lease-time 600;
max-lease-time 72400;
ddns-update-style none;
subnet 10.254.239.0 netmask 255.255.255.224 {
range 10.254.239.10 10.254.239.20;
option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
}
host fantasia {
hardware ethernet 08:00:07:26:c0:a5;
fixed-address fantasia.fugue.com;
}This option specifies the default search domain that
will be provided to clients. Refer to
&man.resolv.conf.5; for more information.This option specifies a comma separated list of
DNS servers that the client should use.
They can be listed by their Fully Qualified Domain Names
(FQDN), as seen in the example, or by
their IP addresses.The subnet mask that will be provided to
clients.The default lease expiry time in seconds. A client
can be configured to override this value. The maximum allowed length of time, in seconds, for a
lease. Should a client request a longer lease, a lease
will still be issued, but it will only be valid for
max-lease-time.The default of disables dynamic
DNS updates. Changing this to
configures the DHCP server to update a
DNS server whenever it hands out a
lease so that the DNS server knows
which IP addresses are associated with
which computers in the network. Do not change the default
setting unless the DNS server has been
configured to support dynamic
DNS.This line creates a pool of available
IP addresses which are reserved for
allocation to DHCP clients. The range
of addresses must be valid for the network or subnet
specified in the previous line.Declares the default gateway that is valid for the
network or subnet specified before the opening
{ bracket.Specifies the hardware MAC address
of a client so that the DHCP server can
recognize the client when it makes a request.Specifies that this host should always be given the
same IP address. Using the hostname is
correct, since the DHCP server will
resolve the hostname before returning the lease
information.This configuration file supports many more options. Refer
to dhcpd.conf(5), installed with the server, for details and
examples.Once the configuration of dhcpd.conf
is complete, enable the DHCP server in
/etc/rc.conf:dhcpd_enable="YES"
dhcpd_ifaces="dc0"Replace the dc0 with the interface (or
interfaces, separated by whitespace) that the
DHCP server should listen on for
DHCP client requests.Start the server by issuing the following command:&prompt.root; service isc-dhcpd startAny future changes to the configuration of the server will
require the dhcpd service to be
stopped and then started using &man.service.8;.The DHCP server uses the following
files. Note that the manual pages are installed with the
server software.DHCPconfiguration files/usr/local/sbin/dhcpdMore information about the
dhcpd server can be found in
dhcpd(8)./usr/local/etc/dhcpd.confThe server configuration file needs to contain all the
information that should be provided to clients, along with
information regarding the operation of the server. This
configuration file is described in dhcpd.conf(5)./var/db/dhcpd.leasesThe DHCP server keeps a database of
leases it has issued in this file, which is written as a
log. Refer to dhcpd.leases(5), which gives a slightly
longer description./usr/local/sbin/dhcrelayThis daemon is used in advanced environments where one
DHCP server forwards a request from a
client to another DHCP server on a
separate network. If this functionality is required,
install the net/isc-dhcp42-relay
package or port. The installation includes dhcrelay(8)
which provides more detail.Domain Name System (DNS)DNSDomain Name System (DNS) is the protocol
through which domain names are mapped to IP
addresses, and vice versa. DNS is
coordinated across the Internet through a somewhat complex
system of authoritative root, Top Level Domain
(TLD), and other smaller-scale name servers,
which host and cache individual domain information. It is not
necessary to run a name server to perform
DNS lookups on a system.BINDIn &os; 10, the Berkeley Internet Name Domain
(BIND) has been removed from the base system
and replaced with Unbound. Unbound as configured in the &os;
Base is a local caching resolver. BIND is
still available from The Ports Collection as dns/bind99 or dns/bind98. In &os; 9 and lower,
BIND is included in &os; Base. The &os;
version provides enhanced security features, a new file system
layout, and automated &man.chroot.8; configuration.
BIND is maintained by the Internet Systems
Consortium.resolverreverse
DNSroot zoneThe following table describes some of the terms associated
with DNS:
DNS TerminologyTermDefinitionForward DNSMapping of hostnames to IP
addresses.OriginRefers to the domain covered in a particular zone
file.named, BINDCommon names for the BIND name server package
within &os;.ResolverA system process through which a machine queries
a name server for zone information.Reverse DNSMapping of IP addresses to
hostnames.Root zoneThe beginning of the Internet zone hierarchy. All
zones fall under the root zone, similar to how all files
in a file system fall under the root directory.ZoneAn individual domain, subdomain, or portion of the
DNS administered by the same
authority.
zonesexamplesExamples of zones:. is how the root zone is
usually referred to in documentation.org. is a Top Level Domain
(TLD) under the root zone.example.org. is a zone
under the org.
TLD.1.168.192.in-addr.arpa is a
zone referencing all IP addresses which
fall under the 192.168.1.*
IP address space.As one can see, the more specific part of a hostname
appears to its left. For example, example.org. is more
specific than org., as
org. is more specific than the root
zone. The layout of each part of a hostname is much like a file
system: the /dev directory falls within the
root, and so on.Reasons to Run a Name ServerName servers generally come in two forms: authoritative
name servers, and caching (also known as resolving) name
servers.An authoritative name server is needed when:One wants to serve DNS information
to the world, replying authoritatively to queries.A domain, such as example.org, is
registered and IP addresses need to be
assigned to hostnames under it.An IP address block requires
reverse DNS entries
(IP to hostname).A backup or second name server, called a slave, will
reply to queries.A caching name server is needed when:A local DNS server may cache and
respond more quickly than querying an outside name
server.When one queries for www.FreeBSD.org, the
resolver usually queries the uplink ISP's
name server, and retrieves the reply. With a local, caching
DNS server, the query only has to be made
once to the outside world by the caching
DNS server. Additional queries will not
have to go outside the local network, since the information is
cached locally.DNS Server Configuration in &os; 10.0
and LaterIn &os; 10.0, BIND has been
replaced with Unbound.
Unbound is a validating caching
resolver only. If an authoritative server is needed, many are
available from the Ports Collection.Unbound is provided in the &os;
base system. By default, it will provide
DNS resolution to the local machine only.
While the base system package can be configured to provide
resolution services beyond the local machine, it is
recommended that such requirements be addressed by installing
Unbound from the &os; Ports
Collection.To enable Unbound, add the
following to /etc/rc.conf:local_unbound_enable="YES"Any existing nameservers in
/etc/resolv.conf will be configured as
forwarders in the new Unbound
configuration.If any of the listed nameservers do not support
DNSSEC, local DNS
resolution will fail. Be sure to test each nameserver and
remove any that fail the test. The following command will
show the trust tree or a failure for a nameserver running on
192.168.1.1:&prompt.user; drill -S FreeBSD.org @192.168.1.1Once each nameserver is confirmed to support
DNSSEC, start
Unbound:&prompt.root; service local_unbound onestartThis will take care of updating
/etc/resolv.conf so that queries for
DNSSEC secured domains will now work. For
example, run the following to validate the FreeBSD.org
DNSSEC trust tree:&prompt.user; drill -S FreeBSD.org
;; Number of trusted keys: 1
;; Chasing: freebsd.org. A
DNSSEC Trust tree:
freebsd.org. (A)
|---freebsd.org. (DNSKEY keytag: 36786 alg: 8 flags: 256)
|---freebsd.org. (DNSKEY keytag: 32659 alg: 8 flags: 257)
|---freebsd.org. (DS keytag: 32659 digest type: 2)
|---org. (DNSKEY keytag: 49587 alg: 7 flags: 256)
|---org. (DNSKEY keytag: 9795 alg: 7 flags: 257)
|---org. (DNSKEY keytag: 21366 alg: 7 flags: 257)
|---org. (DS keytag: 21366 digest type: 1)
| |---. (DNSKEY keytag: 40926 alg: 8 flags: 256)
| |---. (DNSKEY keytag: 19036 alg: 8 flags: 257)
|---org. (DS keytag: 21366 digest type: 2)
|---. (DNSKEY keytag: 40926 alg: 8 flags: 256)
|---. (DNSKEY keytag: 19036 alg: 8 flags: 257)
;; Chase successfulDNS Server Configuration in &os;
9.XIn &os;, the BIND daemon is called
named.FileDescription&man.named.8;The BIND daemon.&man.rndc.8;Name server control utility./etc/namedbDirectory where BIND zone information
resides./etc/namedb/named.confConfiguration file of the daemon.Depending on how a given zone is configured on the server,
the files related to that zone can be found in the
master,
slave, or
dynamic subdirectories
of the /etc/namedb
directory. These files contain the DNS
information that will be given out by the name server in
response to queries.Starting BINDBINDstartingSince BIND is installed by default, configuring it is
relatively simple.The default named configuration
is that of a basic resolving name server, running in a
&man.chroot.8; environment, and restricted to listening on the
local IPv4 loopback address (127.0.0.1). To start the server
one time with this configuration, use the following
command:&prompt.root; service named onestartTo ensure the named daemon is
started at boot each time, put the following line into the
/etc/rc.conf:named_enable="YES"There are many configuration options for
/etc/namedb/named.conf that are beyond
the scope of this document. Other startup options
for named on &os; can be found in
the named_*
flags in /etc/defaults/rc.conf and in
&man.rc.conf.5;. The
section is also a good
read.Configuration FilesBINDconfiguration filesConfiguration files for named
currently reside in
/etc/namedb directory
and will need modification before use unless all that is
needed is a simple resolver. This is where most of the
configuration will be performed./etc/namedb/named.conf// $FreeBSD$
//
// Refer to the named.conf(5) and named(8) man pages, and the documentation
// in /usr/share/doc/bind9 for more details.
//
// If you are going to set up an authoritative server, make sure you
// understand the hairy details of how DNS works. Even with
// simple mistakes, you can break connectivity for affected parties,
// or cause huge amounts of useless Internet traffic.
options {
// All file and path names are relative to the chroot directory,
// if any, and should be fully qualified.
directory "/etc/namedb/working";
pid-file "/var/run/named/pid";
dump-file "/var/dump/named_dump.db";
statistics-file "/var/stats/named.stats";
// If named is being used only as a local resolver, this is a safe default.
// For named to be accessible to the network, comment this option, specify
// the proper IP address, or delete this option.
listen-on { 127.0.0.1; };
// If you have IPv6 enabled on this system, uncomment this option for
// use as a local resolver. To give access to the network, specify
// an IPv6 address, or the keyword "any".
// listen-on-v6 { ::1; };
// These zones are already covered by the empty zones listed below.
// If you remove the related empty zones below, comment these lines out.
disable-empty-zone "255.255.255.255.IN-ADDR.ARPA";
disable-empty-zone "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA";
disable-empty-zone "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA";
// If you've got a DNS server around at your upstream provider, enter
// its IP address here, and enable the line below. This will make you
// benefit from its cache, thus reduce overall DNS traffic in the Internet.
/*
forwarders {
127.0.0.1;
};
*/
// If the 'forwarders' clause is not empty the default is to 'forward first'
// which will fall back to sending a query from your local server if the name
// servers in 'forwarders' do not have the answer. Alternatively you can
// force your name server to never initiate queries of its own by enabling the
// following line:
// forward only;
// If you wish to have forwarding configured automatically based on
// the entries in /etc/resolv.conf, uncomment the following line and
// set named_auto_forward=yes in /etc/rc.conf. You can also enable
// named_auto_forward_only (the effect of which is described above).
// include "/etc/namedb/auto_forward.conf";Just as the comment says, to benefit from an uplink's
cache, forwarders can be enabled here.
Under normal circumstances, a name server will recursively
query the Internet looking at certain name servers until it
finds the answer it is looking for. Having this enabled
will have it query the uplink's name server (or name server
provided) first, taking advantage of its cache. If the
uplink name server in question is a heavily trafficked, fast
name server, enabling this may be worthwhile.127.0.0.1
will not work here. Change this
IP address to a name server at the
uplink. /*
Modern versions of BIND use a random UDP port for each outgoing
query by default in order to dramatically reduce the possibility
of cache poisoning. All users are strongly encouraged to utilize
this feature, and to configure their firewalls to accommodate it.
AS A LAST RESORT in order to get around a restrictive firewall
policy you can try enabling the option below. Use of this option
will significantly reduce your ability to withstand cache poisoning
attacks, and should be avoided if at all possible.
Replace NNNNN in the example with a number between 49160 and 65530.
*/
// query-source address * port NNNNN;
};
// If you enable a local name server, don't forget to enter 127.0.0.1
// first in your /etc/resolv.conf so this server will be queried.
// Also, make sure to enable it in /etc/rc.conf.
// The traditional root hints mechanism. Use this, OR the slave zones below.
zone "." { type hint; file "/etc/namedb/named.root"; };
/* Slaving the following zones from the root name servers has some
significant advantages:
1. Faster local resolution for your users
2. No spurious traffic will be sent from your network to the roots
3. Greater resilience to any potential root server failure/DDoS
On the other hand, this method requires more monitoring than the
hints file to be sure that an unexpected failure mode has not
incapacitated your server. Name servers that are serving a lot
of clients will benefit more from this approach than individual
hosts. Use with caution.
To use this mechanism, uncomment the entries below, and comment
the hint zone above.
As documented at http://dns.icann.org/services/axfr/ these zones:
"." (the root), ARPA, IN-ADDR.ARPA, IP6.ARPA, and ROOT-SERVERS.NET
are available for AXFR from these servers on IPv4 and IPv6:
xfr.lax.dns.icann.org, xfr.cjr.dns.icann.org
*/
/*
zone "." {
type slave;
file "/etc/namedb/slave/root.slave";
masters {
192.5.5.241; // F.ROOT-SERVERS.NET.
};
notify no;
};
zone "arpa" {
type slave;
file "/etc/namedb/slave/arpa.slave";
masters {
192.5.5.241; // F.ROOT-SERVERS.NET.
};
notify no;
};
*/
/* Serving the following zones locally will prevent any queries
for these zones leaving your network and going to the root
name servers. This has two significant advantages:
1. Faster local resolution for your users
2. No spurious traffic will be sent from your network to the roots
*/
// RFCs 1912 and 5735 (and BCP 32 for localhost)
zone "localhost" { type master; file "/etc/namedb/master/localhost-forward.db"; };
zone "127.in-addr.arpa" { type master; file "/etc/namedb/master/localhost-reverse.db"; };
zone "255.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// RFC 1912-style zone for IPv6 localhost address
zone "0.ip6.arpa" { type master; file "/etc/namedb/master/localhost-reverse.db"; };
// "This" Network (RFCs 1912 and 5735)
zone "0.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// Private Use Networks (RFCs 1918 and 5735)
zone "10.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "16.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "17.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "18.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "19.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "20.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "21.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "22.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "23.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "24.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "25.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "26.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "27.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "28.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "29.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "30.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "31.172.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "168.192.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// Link-local/APIPA (RFCs 3927 and 5735)
zone "254.169.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IETF protocol assignments (RFCs 5735 and 5736)
zone "0.0.192.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// TEST-NET-[1-3] for Documentation (RFCs 5735 and 5737)
zone "2.0.192.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "100.51.198.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "113.0.203.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Range for Documentation (RFC 3849)
zone "8.b.d.0.1.0.0.2.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// Domain Names for Documentation and Testing (BCP 32)
zone "test" { type master; file "/etc/namedb/master/empty.db"; };
zone "example" { type master; file "/etc/namedb/master/empty.db"; };
zone "invalid" { type master; file "/etc/namedb/master/empty.db"; };
zone "example.com" { type master; file "/etc/namedb/master/empty.db"; };
zone "example.net" { type master; file "/etc/namedb/master/empty.db"; };
zone "example.org" { type master; file "/etc/namedb/master/empty.db"; };
// Router Benchmark Testing (RFCs 2544 and 5735)
zone "18.198.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "19.198.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IANA Reserved - Old Class E Space (RFC 5735)
zone "240.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "241.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "242.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "243.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "244.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "245.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "246.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "247.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "248.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "249.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "250.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "251.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "252.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "253.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "254.in-addr.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Unassigned Addresses (RFC 4291)
zone "1.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "3.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "4.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "5.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "6.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "7.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "8.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "9.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "a.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "b.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "c.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "d.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "e.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "0.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "1.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "2.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "3.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "4.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "5.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "6.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "7.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "8.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "9.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "a.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "b.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "0.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "1.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "2.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "3.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "4.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "5.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "6.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "7.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 ULA (RFC 4193)
zone "c.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "d.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Link Local (RFC 4291)
zone "8.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "9.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "a.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "b.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IPv6 Deprecated Site-Local Addresses (RFC 3879)
zone "c.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "d.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "e.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
zone "f.e.f.ip6.arpa" { type master; file "/etc/namedb/master/empty.db"; };
// IP6.INT is Deprecated (RFC 4159)
zone "ip6.int" { type master; file "/etc/namedb/master/empty.db"; };
// NB: Do not use the IP addresses below, they are faked, and only
// serve demonstration/documentation purposes!
//
// Example slave zone config entries. It can be convenient to become
// a slave at least for the zone your own domain is in. Ask
// your network administrator for the IP address of the responsible
// master name server.
//
// Do not forget to include the reverse lookup zone!
// This is named after the first bytes of the IP address, in reverse
// order, with ".IN-ADDR.ARPA" appended, or ".IP6.ARPA" for IPv6.
//
// Before starting to set up a master zone, make sure you fully
// understand how DNS and BIND work. There are sometimes
// non-obvious pitfalls. Setting up a slave zone is usually simpler.
//
// NB: Don't blindly enable the examples below. :-) Use actual names
// and addresses instead.
/* An example dynamic zone
key "exampleorgkey" {
algorithm hmac-md5;
secret "sf87HJqjkqh8ac87a02lla==";
};
zone "example.org" {
type master;
allow-update {
key "exampleorgkey";
};
file "/etc/namedb/dynamic/example.org";
};
*/
/* Example of a slave reverse zone
zone "1.168.192.in-addr.arpa" {
type slave;
file "/etc/namedb/slave/1.168.192.in-addr.arpa";
masters {
192.168.1.1;
};
};
*/In named.conf, these are examples
of slave entries for a forward and reverse zone.For each new zone served, a new zone entry must be added
to named.conf.For example, the simplest zone entry for
example.org
can look like:zone "example.org" {
type master;
file "master/example.org";
};The zone is a master, as indicated by the
statement, holding its zone
information in
/etc/namedb/master/example.org
indicated by the statement.zone "example.org" {
type slave;
file "slave/example.org";
};In the slave case, the zone information is transferred
from the master name server for the particular zone, and
saved in the file specified. If and when the master server
dies or is unreachable, the slave name server will have the
transferred zone information and will be able to serve
it.Zone FilesBINDzone filesAn example master zone file for example.org (existing
within /etc/namedb/master/example.org)
is as follows:$TTL 3600 ; 1 hour default TTL
example.org. IN SOA ns1.example.org. admin.example.org. (
2006051501 ; Serial
10800 ; Refresh
3600 ; Retry
604800 ; Expire
300 ; Negative Response TTL
)
; DNS Servers
IN NS ns1.example.org.
IN NS ns2.example.org.
; MX Records
IN MX 10 mx.example.org.
IN MX 20 mail.example.org.
IN A 192.168.1.1
; Machine Names
localhost IN A 127.0.0.1
ns1 IN A 192.168.1.2
ns2 IN A 192.168.1.3
mx IN A 192.168.1.4
mail IN A 192.168.1.5
; Aliases
www IN CNAME example.org.Note that every hostname ending in a . is
an exact hostname, whereas everything without a trailing
. is relative to the origin. For example,
ns1 is translated into
ns1.example.org.The format of a zone file follows:recordname IN recordtype valueDNSrecordsThe most commonly used DNS
records:SOAstart of zone authorityNSan authoritative name serverAa host addressCNAMEthe canonical name for an
aliasMXmail exchangerPTRa domain name pointer (used in reverse
DNS)example.org. IN SOA ns1.example.org. admin.example.org. (
2006051501 ; Serial
10800 ; Refresh after 3 hours
3600 ; Retry after 1 hour
604800 ; Expire after 1 week
300 ) ; Negative Response TTLexample.org.the domain name, also the origin for this
zone file.ns1.example.org.the primary/authoritative name server for this
zone.admin.example.org.the responsible person for this zone,
email address with @
replaced. (admin@example.org becomes
admin.example.org)2006051501the serial number of the file. This must be
incremented each time the zone file is modified.
Nowadays, many admins prefer a
yyyymmddrr format for the serial
number. 2006051501 would mean last
modified 05/15/2006, the latter 01
being the first time the zone file has been modified
this day. The serial number is important as it alerts
slave name servers for a zone when it is
updated. IN NS ns1.example.org.This is an NS entry. Every name server that is going to
reply authoritatively for the zone must have one of these
entries.localhost IN A 127.0.0.1
ns1 IN A 192.168.1.2
ns2 IN A 192.168.1.3
mx IN A 192.168.1.4
mail IN A 192.168.1.5The A record indicates machine names. As seen above,
ns1.example.org would
resolve to 192.168.1.2. IN A 192.168.1.1This line assigns IP address
192.168.1.1 to
the current origin, in this case example.org.www IN CNAME @The canonical name record is usually used for giving
aliases to a machine. In the example,
www is aliased to the
master machine whose name happens to be the
same as the domain name example.org
(192.168.1.1).
CNAMEs can never be used together with another kind of
record for the same hostname.MX record IN MX 10 mail.example.org.The MX record indicates which mail servers are
responsible for handling incoming mail for the zone.
mail.example.org is the
hostname of a mail server, and 10 is the priority of that
mail server.One can have several mail servers, with priorities of
10, 20 and so on. A mail server attempting to deliver to
example.org
would first try the highest priority MX (the record with the
lowest priority number), then the second highest, etc, until
the mail can be properly delivered.For in-addr.arpa zone files (reverse
DNS), the same format is used, except
with PTR entries instead of A or CNAME.$TTL 3600
1.168.192.in-addr.arpa. IN SOA ns1.example.org. admin.example.org. (
2006051501 ; Serial
10800 ; Refresh
3600 ; Retry
604800 ; Expire
300 ) ; Negative Response TTL
IN NS ns1.example.org.
IN NS ns2.example.org.
1 IN PTR example.org.
2 IN PTR ns1.example.org.
3 IN PTR ns2.example.org.
4 IN PTR mx.example.org.
5 IN PTR mail.example.org.This file gives the proper IP address
to hostname mappings for the above fictitious domain.It is worth noting that all names on the right side
of a PTR record need to be fully qualified (i.e., end in
a .).Caching Name ServerBINDcaching name serverA caching name server is a name server whose primary role
is to resolve recursive queries. It simply asks queries of
its own, and remembers the answers for later use.DNSSECBINDDNS security
extensionsDomain Name System Security Extensions, or DNSSEC for
short, is a suite of specifications to protect resolving name
servers from forged DNS data, such as
spoofed DNS records. By using digital
signatures, a resolver can verify the integrity of the record.
Note that DNSSEC only provides integrity via
digitally signing the Resource Records (RRs). It provides neither
confidentiality nor protection against false end-user
assumptions. This means that it cannot protect against people
going to example.net instead of
example.com.
The only thing DNSSEC does is authenticate
that the data has not been compromised in transit. The
security of DNS is an important step in
securing the Internet in general. For more in-depth details
of how DNSSEC works, the relevant
RFCs are a good place to start. See the
list in .The following sections will demonstrate how to enable
DNSSEC for an authoritative
DNS server and a recursive (or caching)
DNS server running BIND
9. While all versions of BIND 9 support
DNSSEC, it is necessary to have at least
version 9.6.2 in order to be able to use the signed root zone
when validating DNS queries. This is
because earlier versions lack the required algorithms to
enable validation using the root zone key. It is strongly
recommended to use the latest version of
BIND 9.7 or later to take advantage of
automatic key updating for the root key, as well as other
features to automatically keep zones signed and signatures up
to date. Where configurations differ between 9.6.2 and 9.7
and later, differences will be pointed out.Recursive DNS Server
ConfigurationEnabling DNSSEC validation of queries
performed by a recursive DNS server
requires a few changes to named.conf.
Before making these changes the root zone key, or trust
anchor, must be acquired. Currently the root zone key is
not available in a file format BIND
understands, so it has to be manually converted into the
proper format. The key itself can be obtained by querying
the root zone for it using dig.
By running&prompt.user; dig +multi +noall +answer DNSKEY . > root.dnskeythe key will end up in root.dnskey.
The contents should look something like this:. 93910 IN DNSKEY 257 3 8 (
AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQ
bSEW0O8gcCjFFVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh
/RStIoO8g0NfnfL2MTJRkxoXbfDaUeVPQuYEhg37NZWA
JQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaDX6RS6CXp
oY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3
LQpzW5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGO
Yl7OyQdXfZ57relSQageu+ipAdTTJ25AsRTAoub8ONGc
LmqrAmRLKBP1dfwhYB4N7knNnulqQxA+Uk1ihz0=
) ; key id = 19036
. 93910 IN DNSKEY 256 3 8 (
AwEAAcaGQEA+OJmOzfzVfoYN249JId7gx+OZMbxy69Hf
UyuGBbRN0+HuTOpBxxBCkNOL+EJB9qJxt+0FEY6ZUVjE
g58sRr4ZQ6Iu6b1xTBKgc193zUARk4mmQ/PPGxn7Cn5V
EGJ/1h6dNaiXuRHwR+7oWh7DnzkIJChcTqlFrXDW3tjt
) ; key id = 34525Do not be alarmed if the obtained keys differ from this
example. They might have changed since these instructions
were last updated. This output actually contains two keys.
The first key in the listing, with the value 257 after the
DNSKEY record type, is the one needed. This value indicates
that this is a Secure Entry Point
(SEP), commonly
known as a Key Signing Key
(KSK). The second
key, with value 256, is a subordinate key, commonly called a
Zone Signing Key
(ZSK). More on
the different key types later in
.Now the key must be verified and formatted so that
BIND can use it. To verify the key,
generate a DS
RR set. Create a
file containing these
RRs with&prompt.user; dnssec-dsfromkey -f root.dnskey . > root.dsThese records use SHA-1 and SHA-256 respectively, and
should look similar to the following example, where the
longer is using SHA-256.. IN DS 19036 8 1
B256BD09DC8DD59F0E0F0D8541B8328DD986DF6E
. IN DS 19036 8 2 49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5The SHA-256 RR can now be compared to
the digest in https://data.iana.org/root-anchors/root-anchors.xml.
To be absolutely sure that the key has not been tampered
with the data in the XML file can be
verified using the PGP signature in
https://data.iana.org/root-anchors/root-anchors.asc.Next, the key must be formatted properly. This differs
a little between BIND versions 9.6.2 and
9.7 and later. In version 9.7 support was added to
automatically track changes to the key and update it as
necessary. This is done using
managed-keys as seen in the example
below. When using the older version, the key is added using
a trusted-keys statement and updates must
be done manually. For BIND 9.6.2 the
format should look like:trusted-keys {
"." 257 3 8
"AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
QxA+Uk1ihz0=";
};For 9.7 the format will instead be:managed-keys {
"." initial-key 257 3 8
"AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
QxA+Uk1ihz0=";
};The root key can now be added to
named.conf either directly or by
including a file containing the key. After these steps,
configure BIND to do
DNSSEC validation on queries by editing
named.conf and adding the following to
the options directive:dnssec-enable yes;
dnssec-validation yes;To verify that it is actually working use
dig to make a query for a signed
zone using the resolver just configured. A successful reply
will contain the AD flag to indicate the
data was authenticated. Running a query such as&prompt.user; dig @resolver +dnssec se ds should return the DS
RR for the .se zone.
In the flags: section the
AD flag should be set, as seen
in:...
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
...The resolver is now capable of authenticating
DNS queries.Authoritative DNS Server
ConfigurationIn order to get an authoritative name server to serve a
DNSSEC signed zone a little more work is
required. A zone is signed using cryptographic keys which
must be generated. It is possible to use only one key for
this. The preferred method however is to have a strong
well-protected Key Signing Key
(KSK) that is
not rotated very often and a Zone Signing Key
(ZSK) that is
rotated more frequently. Information on recommended
operational practices can be found in RFC
4641: DNSSEC Operational
Practices. Practices regarding the root zone can
be found in DNSSEC
Practice Statement for the Root Zone
KSK operator and DNSSEC
Practice Statement for the Root Zone
ZSK operator. The
KSK is used to
build a chain of authority to the data in need of validation
and as such is also called a Secure Entry Point
(SEP) key. A
message digest of this key, called a Delegation Signer
(DS) record,
must be published in the parent zone to establish the trust
chain. How this is accomplished depends on the parent zone
owner. The ZSK
is used to sign the zone, and only needs to be published
there.To enable DNSSEC for the example.com zone
depicted in previous examples, the first step is to use
dnssec-keygen to generate the
KSK and ZSK key pair.
This key pair can utilize different cryptographic
algorithms. It is recommended to use RSA/SHA256 for the
keys and 2048 bits key length should be enough. To generate
the KSK for example.com, run&prompt.user; dnssec-keygen -f KSK -a RSASHA256 -b 2048 -n ZONE example.comand to generate the ZSK, run&prompt.user; dnssec-keygen -a RSASHA256 -b 2048 -n ZONE example.comdnssec-keygen outputs two
files, the public and the private keys in files named
similar to Kexample.com.+005+nnnnn.key
(public) and
Kexample.com.+005+nnnnn.private
(private). The nnnnn part of the file
name is a five digit key ID. Keep track of which key ID
belongs to which key. This is especially important when
having more than one key in a zone. It is also possible to
rename the keys. For each KSK file
do:&prompt.user; mv Kexample.com.+005+nnnnn.key Kexample.com.+005+nnnnn.KSK.key
&prompt.user; mv Kexample.com.+005+nnnnn.private Kexample.com.+005+nnnnn.KSK.privateFor the ZSK files, substitute
KSK for ZSK as
necessary. The files can now be included in the zone file,
using the $include statement. It should
look something like this:$include Kexample.com.+005+nnnnn.KSK.key ; KSK
$include Kexample.com.+005+nnnnn.ZSK.key ; ZSKFinally, sign the zone and tell BIND
to use the signed zone file. To sign a zone
dnssec-signzone is used. The
command to sign the zone example.com, located in
example.com.db would look similar
to&prompt.user; dnssec-signzone -o
example.com -k Kexample.com.+005+nnnnn.KSK example.com.db
Kexample.com.+005+nnnnn.ZSK.keyThe key supplied to the argument is
the KSK and the other key file is the
ZSK that should be used in the signing.
It is possible to supply more than one
KSK and ZSK, which
will result in the zone being signed with all supplied keys.
This can be needed to supply zone data signed using more
than one algorithm. The output of
dnssec-signzone is a zone file
with all RRs signed. This output will
end up in a file with the extension
.signed, such as
example.com.db.signed. The
DS records will
also be written to a separate file
dsset-example.com. To use this signed
zone just modify the zone directive in
named.conf to use
example.com.db.signed. By default, the
signatures are only valid 30 days, meaning that the zone
needs to be resigned in about 15 days to be sure that
resolvers are not caching records with stale signatures. It
is possible to make a script and a cron job to do this. See
relevant manuals for details.Be sure to keep private keys confidential, as with all
cryptographic keys. When changing a key it is best to
include the new key into the zone, while still signing with
the old one, and then move over to using the new key to
sign. After these steps are done the old key can be removed
from the zone. Failure to do this might render the
DNS data unavailable for a time, until
the new key has propagated through the
DNS hierarchy. For more information on
key rollovers and other DNSSEC
operational issues, see RFC
4641: DNSSEC Operational
practices.Automation Using BIND 9.7 or
LaterBeginning with BIND version 9.7 a new
feature called Smart Signing was
introduced. This feature aims to make the key management
and signing process simpler by automating parts of the task.
By putting the keys into a directory called a
key repository, and using the new
option auto-dnssec, it is possible to
create a dynamic zone which will be resigned as needed. To
update this zone use nsupdate
with the new option .
rndc has also grown the ability
to sign zones with keys in the key repository, using the
option . To tell
BIND to use this automatic signing and
zone updating for example.com, add the
following to named.conf:zone example.com {
type master;
key-directory "/etc/named/keys";
update-policy local;
auto-dnssec maintain;
file "/etc/named/dynamic/example.com.zone";
};After making these changes, generate keys for the zone
as explained in , put those
keys in the key repository given as the argument to the
key-directory in the zone configuration
and the zone will be signed automatically. Updates to a
zone configured this way must be done using
nsupdate, which will take care of
re-signing the zone with the new data added. For further
details, see and the
BIND documentation.SecurityAlthough BIND is the most common implementation of
DNS, there is always the issue of security.
Possible and exploitable security holes are sometimes
found.While &os; automatically drops
named into a &man.chroot.8;
environment; there are several other security mechanisms in
place which could help to lure off possible
DNS service attacks.It is always good idea to read
CERT's security
advisories and to subscribe to the &a.security-notifications;
to stay up to date with the current Internet and &os; security
issues.If a problem arises, keeping sources up to date and
having a fresh build of named
may help.Further ReadingBIND/named manual pages:
&man.rndc.8; &man.named.8; &man.named.conf.5; &man.nsupdate.1;
&man.dnssec-signzone.8; &man.dnssec-keygen.8;Official
ISC BIND PageOfficial
ISC BIND ForumO'Reilly
DNS and BIND 5th
EditionRoot
DNSSECDNSSEC
Trust Anchor Publication for the Root
ZoneRFC1034
- Domain Names - Concepts and FacilitiesRFC1035
- Domain Names - Implementation and
SpecificationRFC4033
- DNS Security Introduction and
RequirementsRFC4034
- Resource Records for the DNS
Security ExtensionsRFC4035
- Protocol Modifications for the DNS
Security ExtensionsRFC4641
- DNSSEC Operational PracticesRFC 5011
- Automated Updates of DNS Security
(DNSSEC
Trust AnchorsApache HTTP ServerMurrayStokelyContributed by web serverssetting upApacheThe open source
Apache HTTP Server is the most widely
used web server. &os; does not install this web server by
default, but it can be installed from the
www/apache24 package or port.This section summarizes how to configure and start version
2.x of the Apache HTTP
Server on &os;. For more detailed information
about Apache 2.X and its
configuration directives, refer to httpd.apache.org.Configuring and Starting ApacheApacheconfiguration fileIn &os;, the main Apache HTTP
Server configuration file is installed as
/usr/local/etc/apache2x/httpd.conf,
where x represents the version
number. This ASCII text file begins
comment lines with a #. The most
frequently modified directives are:ServerRoot "/usr/local"Specifies the default directory hierarchy for the
Apache installation.
Binaries are stored in the bin and
sbin subdirectories of the server
root and configuration files are stored in the etc/apache2x
subdirectory.ServerAdmin you@example.comChange this to the email address to receive problems
with the server. This address also appears on some
server-generated pages, such as error documents.ServerName
www.example.com:80Allows an administrator to set a hostname which is
sent back to clients for the server. For example,
www can be used instead of the
actual hostname. If the system does not have a
registered DNS name, enter its
IP address instead. If the server
will listen on an alternate report, change
80 to the alternate port
number.DocumentRoot
"/usr/local/www/apache2x/data"The directory where documents will be served from.
By default, all requests are taken from this directory,
but symbolic links and aliases may be used to point to
other locations.It is always a good idea to make a backup copy of the
default Apache configuration file
before making changes. When the configuration of
Apache is complete, save the file
and verify the configuration using
apachectl. Running apachectl
configtest should return Syntax
OK.Apachestarting or stoppingTo launch Apache at system
startup, add the following line to
/etc/rc.conf:apache24_enable="YES"If Apache should be started
with non-default options, the following line may be added to
/etc/rc.conf to specify the needed
flags:apache24_flags=""If apachectl does not report
configuration errors, start httpd
now:&prompt.root; service apache24 startThe httpd service can be tested by
entering
http://localhost
in a web browser, replacing
localhost with the fully-qualified
domain name of the machine running httpd.
The default web page that is displayed is
/usr/local/www/apache24/data/index.html.The Apache configuration can be
tested for errors after making subsequent configuration
changes while httpd is running using the
following command:&prompt.root; service apache24 configtestIt is important to note that
configtest is not an &man.rc.8; standard,
and should not be expected to work for all startup
scripts.Virtual HostingVirtual hosting allows multiple websites to run on one
Apache server. The virtual hosts
can be IP-based or
name-based.
IP-based virtual hosting uses a different
IP address for each website. Name-based
virtual hosting uses the clients HTTP/1.1 headers to figure
out the hostname, which allows the websites to share the same
IP address.To setup Apache to use
name-based virtual hosting, add a
VirtualHost block for each website. For
example, for the webserver named www.domain.tld with a
virtual domain of www.someotherdomain.tld,
add the following entries to
httpd.conf:<VirtualHost *>
ServerName www.domain.tld
DocumentRoot /www/domain.tld
</VirtualHost>
<VirtualHost *>
ServerName www.someotherdomain.tld
DocumentRoot /www/someotherdomain.tld
</VirtualHost>For each virtual host, replace the values for
ServerName and
DocumentRoot with the values to be
used.For more information about setting up virtual hosts,
consult the official Apache
documentation at: http://httpd.apache.org/docs/vhosts/.Apache ModulesApachemodulesApache uses modules to augment
the functionality provided by the basic server. Refer to http://httpd.apache.org/docs/current/mod/
for a complete listing of and the configuration details for
the available modules.In &os;, some modules can be compiled with the
www/apache24 port. Type make
config within
/usr/ports/www/apache24 to see which
modules are available and which are enabled by default. If
the module is not compiled with the port, the &os; Ports
Collection provides an easy way to install many modules. This
section describes three of the most commonly used
modules.mod_sslweb serverssecureSSLcryptographyThe mod_ssl module uses the
OpenSSL library to provide strong
cryptography via the Secure Sockets Layer
(SSLv3) and Transport Layer Security
(TLSv1) protocols. This module provides
everything necessary to request a signed certificate from a
trusted certificate signing authority to run a secure web
server on &os;.In &os;, mod_ssl module is enabled
by default in both the package and the port. The available
configuration directives are explained at http://httpd.apache.org/docs/current/mod/mod_ssl.html.mod_perlmod_perlPerlThe
mod_perl module makes it possible to
write Apache modules in
Perl. In addition, the
persistent interpreter embedded in the server avoids the
overhead of starting an external interpreter and the penalty
of Perl start-up time.The mod_perl can be installed using
the www/mod_perl2 package or port.
Documentation for using this module can be found at http://perl.apache.org/docs/2.0/index.html.mod_phpTomRhodesWritten by mod_phpPHPPHP: Hypertext Preprocessor
(PHP) is a general-purpose scripting
language that is especially suited for web development.
Capable of being embedded into HTML, its
syntax draws upon C, &java;, and
Perl with the intention of
allowing web developers to write dynamically generated
webpages quickly.To gain support for PHP5 for the
Apache web server, install the
- www/mod_php5 package or port. This will
+ www/mod_php56 package or port. This will
install and configure the modules required to support
dynamic PHP applications. The
installation will automatically add this line to
/usr/local/etc/apache24/httpd.conf:LoadModule php5_module libexec/apache24/libphp5.soThen, perform a graceful restart to load the
PHP module:&prompt.root; apachectl gracefulThe PHP support provided by
- www/mod_php5 is limited. Additional
+ www/mod_php56 is limited. Additional
support can be installed using the
- lang/php5-extensions port which provides
+ lang/php56-extensions port which provides
a menu driven interface to the available
PHP extensions.Alternatively, individual extensions can be installed
using the appropriate port. For instance, to add
PHP support for the
MySQL database server, install
- databases/php5-mysql.
+ databases/php56-mysql.
After installing an extension, the
Apache server must be reloaded to
pick up the new configuration changes:&prompt.root; apachectl gracefulDynamic Websitesweb serversdynamicIn addition to mod_perl and
mod_php, other languages are
available for creating dynamic web content. These include
Django and
Ruby on Rails.DjangoPythonDjangoDjango is a BSD-licensed
framework designed to allow developers to write high
performance, elegant web applications quickly. It provides
an object-relational mapper so that data types are developed
as Python objects. A rich
dynamic database-access API is provided
for those objects without the developer ever having to write
SQL. It also provides an extensible
template system so that the logic of the application is
separated from the HTML
presentation.Django depends on mod_python, and
an SQL database engine. In &os;, the
www/py-django port automatically installs
mod_python and supports the
PostgreSQL,
MySQL, or
SQLite databases, with the
default being SQLite. To change
the database engine, type make config
within /usr/ports/www/py-django, then
install the port.Once Django is installed, the
application will need a project directory along with the
Apache configuration in order to
use the embedded Python
interpreter. This interpreter is used to call the
application for specific URLs on the
site.To configure Apache to pass
requests for certain URLs to the web
application, add the following to
httpd.conf, specifying the full path to
the project directory:<Location "/">
SetHandler python-program
PythonPath "['/dir/to/the/django/packages/'] + sys.path"
PythonHandler django.core.handlers.modpython
SetEnv DJANGO_SETTINGS_MODULE mysite.settings
PythonAutoReload On
PythonDebug On
</Location>Refer to https://docs.djangoproject.com/en/1.6/
for more information on how to use
Django.Ruby on RailsRuby on RailsRuby on Rails is another open
source web framework that provides a full development stack.
It is optimized to make web developers more productive and
capable of writing powerful applications quickly. On &os;,
it can be installed using the
www/rubygem-rails package or port.Refer to http://rubyonrails.org/documentation
for more information on how to use Ruby on
Rails.File Transfer Protocol (FTP)FTP
serversThe File Transfer Protocol (FTP) provides
users with a simple way to transfer files to and from an
FTP server. &os; includes
FTP server software,
ftpd, in the base system.&os; provides several configuration files for controlling
access to the FTP server. This section
summarizes these files. Refer to &man.ftpd.8; for more details
about the built-in FTP server.ConfigurationThe most important configuration step is deciding which
accounts will be allowed access to the FTP
server. A &os; system has a number of system accounts which
should not be allowed FTP access. The list
of users disallowed any FTP access can be
found in /etc/ftpusers. By default, it
includes system accounts. Additional users that should not be
allowed access to FTP can be added.In some cases it may be desirable to restrict the access
of some users without preventing them completely from using
FTP. This can be accomplished be creating
/etc/ftpchroot as described in
&man.ftpchroot.5;. This file lists users and groups subject
to FTP access restrictions.FTPanonymousTo enable anonymous FTP access to the
server, create a user named ftp on the &os; system. Users
will then be able to log on to the
FTP server with a username of
ftp or anonymous. When prompted for
the password, any input will be accepted, but by convention,
an email address should be used as the password. The
FTP server will call &man.chroot.2; when an
anonymous user logs in, to restrict access to only the home
directory of the ftp user.There are two text files that can be created to specify
welcome messages to be displayed to FTP
clients. The contents of
/etc/ftpwelcome will be displayed to
users before they reach the login prompt. After a successful
login, the contents of
/etc/ftpmotd will be displayed. Note
that the path to this file is relative to the login
environment, so the contents of
~ftp/etc/ftpmotd would be displayed for
anonymous users.Once the FTP server has been
configured, set the appropriate variable in
/etc/rc.conf to start the service during
boot:ftpd_enable="YES"To start the service now:&prompt.root; service ftpd startTest the connection to the FTP server
by typing:&prompt.user; ftp localhostsysloglog filesFTPThe ftpd daemon uses
&man.syslog.3; to log messages. By default, the system log
daemon will write messages related to FTP
in /var/log/xferlog. The location of
the FTP log can be modified by changing the
following line in
/etc/syslog.conf:ftp.info /var/log/xferlogFTPanonymousBe aware of the potential problems involved with running
an anonymous FTP server. In particular,
think twice about allowing anonymous users to upload files.
It may turn out that the FTP site becomes
a forum for the trade of unlicensed commercial software or
worse. If anonymous FTP uploads are
required, then verify the permissions so that these files
can not be read by other anonymous users until they have
been reviewed by an administrator.File and Print Services for µsoft.windows; Clients
(Samba)Samba serverMicrosoft Windowsfile serverWindows clientsprint serverWindows clientsSamba is a popular open source
software package that provides file and print services using the
SMB/CIFS protocol. This protocol is built
into µsoft.windows; systems. It can be added to
non-µsoft.windows; systems by installing the
Samba client libraries. The protocol
allows clients to access shared data and printers. These shares
can be mapped as a local disk drive and shared printers can be
used as if they were local printers.On &os;, the Samba client
libraries can be installed using the
net/samba-smbclient port or package. The
client provides the ability for a &os; system to access
SMB/CIFS shares in a µsoft.windows;
network.A &os; system can also be configured to act as a
Samba server. This allows the
administrator to create SMB/CIFS shares on
the &os; system which can be accessed by clients running
µsoft.windows; or the Samba
client libraries. In order to configure a
Samba server on &os;, the
net/samba36 port or package must first be
installed. The rest of this section provides an overview of how
to configure a Samba server on
&os;.ConfigurationA default Samba configuration
file is installed as
/usr/local/share/examples/samba36/smb.conf.default.
This file must be copied to
/usr/local/etc/smb.conf and customized
before Samba can be used.Runtime configuration information for
Samba is found in
smb.conf, such as definitions of the
printers and file system shares that will
be shared with &windows; clients. The
Samba package includes a web based
tool called swat which provides a
simple way for configuring
smb.conf.Using the Samba Web Administration Tool (SWAT)The Samba Web Administration Tool (SWAT) runs as a
daemon from inetd. Therefore,
inetd must be enabled as shown in
. To enable
swat, uncomment the following
line in /etc/inetd.conf:swat stream tcp nowait/400 root /usr/local/sbin/swat swatAs explained in ,
the inetd configuration must be
reloaded after this configuration file is changed.Once swat has been enabled,
use a web browser to connect to http://localhost:901.
At first login, enter the credentials for root.Once logged in, the main
Samba configuration page and the
system documentation will be available. Begin configuration
by clicking on the Globals tab. The
Globals section corresponds to the
variables that are set in the [global]
section of
/usr/local/etc/smb.conf.Global SettingsWhether swat is used or
/usr/local/etc/smb.conf is edited
directly, the first directives encountered when configuring
Samba are:workgroupThe domain name or workgroup name for the
computers that will be accessing this server.netbios nameThe NetBIOS name by which a
Samba server is known. By
default it is the same as the first component of the
host's DNS name.server stringThe string that will be displayed in the output of
net view and some other
networking tools that seek to display descriptive text
about the server.Security SettingsTwo of the most important settings in
/usr/local/etc/smb.conf are the
security model and the backend password format for client
users. The following directives control these
options:securityThe two most common options are
security = share and
security = user. If the clients
use usernames that are the same as their usernames on
the &os; machine, user level security should be
used. This is the default security policy and it
requires clients to first log on before they can
access shared resources.In share level security, clients do not need to
log onto the server with a valid username and password
before attempting to connect to a shared resource.
This was the default security model for older versions
of Samba.passdb backendNIS+LDAPSQL databaseSamba has several
different backend authentication models. Clients may
be authenticated with LDAP, NIS+, an SQL database,
or a modified password file. The default
authentication method is smbpasswd,
and that is all that will be covered here.Assuming that the default smbpasswd
backend is used,
/usr/local/etc/samba/smbpasswd
must be created to allow Samba to
authenticate clients. To provide &unix; user accounts
access from &windows; clients, use the following command to
add each required user to that file:&prompt.root; smbpasswd -a usernameThe recommended backend is now
tdbsam. If this backend is selected,
use the following command to add user accounts:&prompt.root; pdbedit -a -u usernameThis section has only mentioned the most commonly used
settings. Refer to the Official
Samba HOWTO for additional information about the
available configuration options.Starting SambaTo enable Samba at boot time,
add the following line to
/etc/rc.conf:samba_enable="YES"Alternately, its services can be started
separately:nmbd_enable="YES"smbd_enable="YES"To start Samba now:&prompt.root; service samba start
Starting SAMBA: removing stale tdbs :
Starting nmbd.
Starting smbd.Samba consists of three
separate daemons. Both the nmbd
and smbd daemons are started by
samba_enable. If winbind name resolution
services are enabled in smb.conf, the
winbindd daemon is started as
well.Samba may be stopped at any
time by typing:&prompt.root; service samba stopSamba is a complex software
suite with functionality that allows broad integration with
µsoft.windows; networks. For more information about
functionality beyond the basic configuration described here,
refer to http://www.samba.org.Clock Synchronization with NTPNTPntpdOver time, a computer's clock is prone to drift. This is
problematic as many network services require the computers on a
network to share the same accurate time. Accurate time is also
needed to ensure that file timestamps stay consistent. The
Network Time Protocol (NTP) is one way to
provide clock accuracy in a network.&os; includes &man.ntpd.8; which can be configured to query
other NTP servers in order to synchronize the
clock on that machine or to provide time services to other
computers in the network. The servers which are queried can be
local to the network or provided by an ISP.
In addition, an online
list of publicly accessible NTP
servers is available. When choosing a public
NTP server, select one that is geographically
close and review its usage policy.Choosing several NTP servers is
recommended in case one of the servers becomes unreachable or
its clock proves unreliable. As ntpd
receives responses, it favors reliable servers over the less
reliable ones.This section describes how to configure
ntpd on &os;. Further documentation
can be found in /usr/share/doc/ntp/ in HTML
format.NTP ConfigurationNTPntp.confOn &os;, the built-in ntpd can
be used to synchronize a system's clock. To enable
ntpd at boot time, add
ntpd_enable="YES" to
/etc/rc.conf. Additional variables can
be specified in /etc/rc.conf. Refer to
&man.rc.conf.5; and &man.ntpd.8; for
details.This application reads /etc/ntp.conf
to determine which NTP servers to query.
Here is a simple example of an
/etc/ntp.conf: Sample /etc/ntp.confserver ntplocal.example.com prefer
server timeserver.example.org
server ntp2a.example.net
driftfile /var/db/ntp.driftThe format of this file is described in &man.ntp.conf.5;.
The server option specifies which servers
to query, with one server listed on each line. If a server
entry includes prefer, that server is
preferred over other servers. A response from a preferred
server will be discarded if it differs significantly from
other servers' responses; otherwise it will be used. The
prefer argument should only be used for
NTP servers that are known to be highly
accurate, such as those with special time monitoring
hardware.The driftfile entry specifies which
file is used to store the system clock's frequency offset.
ntpd uses this to automatically
compensate for the clock's natural drift, allowing it to
maintain a reasonably correct setting even if it is cut off
from all external time sources for a period of time. This
file also stores information about previous responses
from NTP servers. Since this file contains
internal information for NTP, it should not
be modified.By default, an NTP server is accessible
to any network host. The restrict option
in /etc/ntp.conf can be used to control
which systems can access the server. For example, to deny all
machines from accessing the NTP server, add
the following line to
/etc/ntp.conf:restrict default ignoreThis will also prevent access from other
NTP servers. If there is a need to
synchronize with an external NTP server,
allow only that specific server. Refer to &man.ntp.conf.5;
for more information.To allow machines within the network to synchronize their
clocks with the server, but ensure they are not allowed to
configure the server or be used as peers to synchronize
against, instead use:restrict 192.168.1.0 mask 255.255.255.0 nomodify notrapwhere 192.168.1.0 is the local
network address and 255.255.255.0 is the network's
subnet mask.Multiple restrict entries are
supported. For more details, refer to the Access
Control Support subsection of
&man.ntp.conf.5;.Once ntpd_enable="YES" has been added
to /etc/rc.conf,
ntpd can be started now without
rebooting the system by typing:&prompt.root; service ntpd startUsing NTP with a
PPP Connectionntpd does not need a permanent
connection to the Internet to function properly. However, if
a PPP connection is configured to dial out
on demand, NTP traffic should be prevented
from triggering a dial out or keeping the connection alive.
This can be configured with filter
directives in /etc/ppp/ppp.conf. For
example: set filter dial 0 deny udp src eq 123
# Prevent NTP traffic from initiating dial out
set filter dial 1 permit 0 0
set filter alive 0 deny udp src eq 123
# Prevent incoming NTP traffic from keeping the connection open
set filter alive 1 deny udp dst eq 123
# Prevent outgoing NTP traffic from keeping the connection open
set filter alive 2 permit 0/0 0/0For more details, refer to the
PACKET FILTERING section in &man.ppp.8; and
the examples in
/usr/share/examples/ppp/.Some Internet access providers block low-numbered ports,
preventing NTP from functioning since replies never reach
the machine.iSCSI Initiator and Target
ConfigurationiSCSI is a way to share storage over a
network. Unlike NFS, which works at the file
system level, iSCSI works at the block device
level.In iSCSI terminology, the system that
shares the storage is known as the target.
The storage can be a physical disk, or an area representing
multiple disks or a portion of a physical disk. For example, if
the disk(s) are formatted with ZFS, a zvol
can be created to use as the iSCSI
storage.The clients which access the iSCSI
storage are called initiators. To
initiators, the storage available through
iSCSI appears as a raw, unformatted disk
known as a LUN. Device nodes for the disk
appear in /dev/ and the device must be
separately formatted and mounted.Beginning with 10.0-RELEASE, &os; provides a native,
kernel-based iSCSI target and initiator.
This section describes how to configure a &os; system as a
target or an initiator.Configuring an iSCSI TargetThe native iSCSI target is supported
starting with &os; 10.0-RELEASE. To use
iSCSI in older versions of &os;, install
a userspace target from the Ports Collection, such as
net/istgt. This chapter only describes
the native target.To configure an iSCSI target, create
the /etc/ctl.conf configuration file, add
a line to /etc/rc.conf to make sure the
&man.ctld.8; daemon is automatically started at boot, and then
start the daemon.The following is an example of a simple
/etc/ctl.conf configuration file. Refer
to &man.ctl.conf.5; for a more complete description of this
file's available options.portal-group pg0 {
discovery-auth-group no-authentication
listen 0.0.0.0
listen [::]
}
target iqn.2012-06.com.example:target0 {
auth-group no-authentication
portal-group pg0
lun 0 {
path /data/target0-0
size 4G
}
}The first entry defines the pg0 portal
group. Portal groups define which network addresses the
&man.ctld.8; daemon will listen on. The
discovery-auth-group no-authentication
entry indicates that any initiator is allowed to perform
iSCSI target discovery without
authentication. Lines three and four configure &man.ctld.8;
to listen on all IPv4
(listen 0.0.0.0) and
IPv6 (listen [::])
addresses on the default port of 3260.It is not necessary to define a portal group as there is a
built-in portal group called default. In
this case, the difference between default
and pg0 is that with
default, target discovery is always denied,
while with pg0, it is always
allowed.The second entry defines a single target. Target has two
possible meanings: a machine serving iSCSI
or a named group of LUNs. This example
uses the latter meaning, where
iqn.2012-06.com.example:target0 is the
target name. This target name is suitable for testing
purposes. For actual use, change
com.example to the real domain name,
reversed. The 2012-06 represents the year
and month of acquiring control of that domain name, and
target0 can be any value. Any number of
targets can be defined in this configuration file.The auth-group no-authentication line
allows all initiators to connect to the specified target and
portal-group pg0 makes the target reachable
through the pg0 portal group.The next section defines the LUN. To
the initiator, each LUN will be visible as
a separate disk device. Multiple LUNs can
be defined for each target. Each LUN is
identified by a number, where LUN 0 is
mandatory. The path /data/target0-0 line
defines the full path to a file or zvol backing the
LUN. That path must exist before starting
&man.ctld.8;. The second line is optional and specifies the
size of the LUN.Next, to make sure the &man.ctld.8; daemon is started at
boot, add this line to
/etc/rc.conf:ctld_enable="YES"To start &man.ctld.8; now, run this command:&prompt.root; service ctld startAs the &man.ctld.8; daemon is started, it reads
/etc/ctl.conf. If this file is edited
after the daemon starts, use this command so that the changes
take effect immediately:&prompt.root; service ctld reloadAuthenticationThe previous example is inherently insecure as it uses
no authentication, granting anyone full access to all
targets. To require a username and password to access
targets, modify the configuration as follows:auth-group ag0 {
chap username1 secretsecret
chap username2 anothersecret
}
portal-group pg0 {
discovery-auth-group no-authentication
listen 0.0.0.0
listen [::]
}
target iqn.2012-06.com.example:target0 {
auth-group ag0
portal-group pg0
lun 0 {
path /data/target0-0
size 4G
}
}The auth-group section defines
username and password pairs. An initiator trying to connect
to iqn.2012-06.com.example:target0 must
first specify a defined username and secret. However,
target discovery is still permitted without authentication.
To require target discovery authentication, set
discovery-auth-group to a defined
auth-group name instead of
no-authentication.It is common to define a single exported target for
every initiator. As a shorthand for the syntax above, the
username and password can be specified directly in the
target entry:target iqn.2012-06.com.example:target0 {
portal-group pg0
chap username1 secretsecret
lun 0 {
path /data/target0-0
size 4G
}
}Configuring an iSCSI InitiatorThe iSCSI initiator described in this
section is supported starting with &os; 10.0-RELEASE. To
use the iSCSI initiator available in
older versions, refer to &man.iscontrol.8;.The iSCSI initiator requires that the
&man.iscsid.8; daemon is running. This daemon does not use a
configuration file. To start it automatically at boot, add
this line to /etc/rc.conf:iscsid_enable="YES"To start &man.iscsid.8; now, run this command:&prompt.root; service iscsid startConnecting to a target can be done with or without an
/etc/iscsi.conf configuration file. This
section demonstrates both types of connections.Connecting to a Target Without a Configuration
FileTo connect an initiator to a single target, specify the
IP address of the portal and the name of
the target:&prompt.root; iscsictl -A -p 10.10.10.10 -t iqn.2012-06.com.example:target0To verify if the connection succeeded, run
iscsictl without any arguments. The
output should look similar to this:Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.10 Connected: da0In this example, the iSCSI session
was successfully established, with
/dev/da0 representing the attached
LUN. If the
iqn.2012-06.com.example:target0 target
exports more than one LUN, multiple
device nodes will be shown in that section of the
output:Connected: da0 da1 da2.Any errors will be reported in the output, as well as
the system logs. For example, this message usually means
that the &man.iscsid.8; daemon is not running:Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.10 Waiting for iscsid(8)The following message suggests a networking problem,
such as a wrong IP address or
port:Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.11 Connection refusedThis message means that the specified target name is
wrong:Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.10 Not foundThis message means that the target requires
authentication:Target name Target portal State
iqn.2012-06.com.example:target0 10.10.10.10 Authentication failedTo specify a CHAP username and
secret, use this syntax:&prompt.root; iscsictl -A -p 10.10.10.10 -t iqn.2012-06.com.example:target0 -u user -s secretsecretConnecting to a Target with a Configuration
FileTo connect using a configuration file, create
/etc/iscsi.conf with contents like
this:t0 {
TargetAddress = 10.10.10.10
TargetName = iqn.2012-06.com.example:target0
AuthMethod = CHAP
chapIName = user
chapSecret = secretsecret
}The t0 specifies a nickname for the
configuration file section. It will be used by the
initiator to specify which configuration to use. The other
lines specify the parameters to use during connection. The
TargetAddress and
TargetName are mandatory, whereas the
other options are optional. In this example, the
CHAP username and secret are
shown.To connect to the defined target, specify the
nickname:&prompt.root; iscsictl -An t0Alternately, to connect to all targets defined in the
configuration file, use:&prompt.root; iscsictl -AaTo make the initiator automatically connect to all
targets in /etc/iscsi.conf, add the
following to /etc/rc.conf:iscsictl_enable="YES"
iscsictl_flags="-Aa"