Index: head/en_US.ISO8859-1/books/handbook/virtualization/chapter.xml
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@@ -30,6 +30,16 @@
bhyve section by
+
+
+
+
+ Benedict
+ Reuschling
+
+ Xen section by
+
+
@@ -1354,17 +1364,338 @@
-
+ &xen; can migrate VMs between different &xen; servers. When
+ the two xen hosts share the same underlying storage, the
+ migration can be done without having to shut the VM down first.
+ Instead, the migration is performed live while the DomU is
+ running and there is no need to restart it or plan a downtime.
+ This is useful in maintenance scenarios or upgrade windows to
+ ensure that the services provided by the DomU are still
+ provided. Many more features of &xen; are listed on the Xen
+ Wiki Overview page. Note that not all features are
+ supported on &os; yet.
+
+
+ Hardware Requirements for &xen; Dom0
+
+ To run the &xen; hypervisor on a host, certain hardware
+ functionality is required. Hardware virtualized domains
+ require Extended Page Table (EPT)
+ and Input/Output Memory Management Unit (IOMMU)
+ support in the host processor.
+
+
+
+ &xen; Dom0 Control Domain Setup
+
+ The emulators/xen package works with
+ &os; 11 amd64 binary snapshots and equivalent systems
+ built from source. This example assumes VNC output for
+ unprivileged domains which is accessed from a another system
+ using a tool such as net/tightvnc.
+
+ Install emulators/xen:
+
+ &prompt.root; pkg install xen
+
+ Configuration files must be edited to prepare the host
+ for the Dom0 integration. An entry to
+ /etc/sysctl.conf disables the limit on
+ how many pages of memory are allowed to be wired. Otherwise,
+ domU VMs with higher memory requirements will not run.
+
+ &prompt.root; sysrc -f /etc/sysctl.conf vm.max_wired=-1
+
+ Another memory-related setting involves changing
+ /etc/login.conf, setting the
+ memorylocked option to
+ unlimited. Otherwise, creating DomU
+ domains may fail with Cannot allocate
+ memory errors. After making the change to
+ /etc/login.conf, run
+ cap_mkdb to update the capability database.
+ See for
+ details.
+
+ &prompt.root; sed -i '' -e 's/memorylocked=64K/memorylocked=unlimited/' /etc/login.conf
+&prompt.root; cap_mkdb /etc/login.conf
+
+ Add an entry for the &xen; console to
+ /etc/ttys:
+
+ &prompt.root; echo 'xc0 "/usr/libexec/getty Pc" xterm on secure' >> /etc/ttys
+
+ Selecting a &xen; kernel in
+ /boot/loader.conf activates the Dom0.
+ &xen; also requires resources like CPU and memory from the
+ host machine for itself and other DomU domains. How much CPU
+ and memory depends on the individual requirements and hardware
+ capabilities. In this example, 8 GB of memory and 4
+ virtual CPUs are made available for the Dom0. The serial
+ console is also activated and logging options are
+ defined.
+
+ &prompt.root; sysrc -f /boot/loader.conf hw.pci.mcfg=0
+&prompt.root; xen_kernel="/boot/xen"
+&prompt.root; xen_cmdline="dom0_mem=8192M dom0_max_vcpus=4 dom0pvh=1 console=com1,vga com1=115200,8n1 guest_loglvl=all loglvl=all"
+
+ Log files that &xen; creates for the Dom0 and DomU VMs
+ are stored in /var/log/xen. This
+ directory does not exist by default and must be
+ created.
+
+ &prompt.root; mkdir -p /var/log/xen
+&prompt.root; chmod 644 /var/log/xen
+
+ &xen; provides a boot menu to activate and de-activate
+ the hypervisor on demand in
+ /boot/menu.rc.local:
+
+ &prompt.root; echo "try-include /boot/xen.4th" >> /boot/menu.rc.local
+
+ Activate the xencommons service during system
+ startup:
+
+ &prompt.root; sysrc xencommons_enable=yes
+
+ These settings are enough to start a Dom0-enabled
+ system. However, it lacks network functionality for the
+ DomU machines. To fix that, define a bridged interface with
+ the main NIC of the system which the DomU VMs can use to
+ connect to the network. Replace
+ igb0 with the host network
+ interface name.
+
+ &prompt.root; sysrc autobridge_interfaces=bridge0
+&prompt.root; sysrc autobridge_bridge0=igb0
+&prompt.root; sysrc ifconfig_bridge0=SYNCDHCP
+
+ Restart the host to load the &xen; kernel and start the
+ Dom0.
+
+ &prompt.root; reboot
+
+ After successfully booting the &xen; kernel and logging
+ into the system again, the &xen; management tool
+ xl is used to show information about the
+ domains.
+
+ &prompt.root; xl list
+Name ID Mem VCPUs State Time(s)
+Domain-0 0 8192 4 r----- 962.0
+
+ The output confirms that the Dom0 (called
+ Domain-0) has the ID 0
+ and is running. It also has the memory and virtual CPUs
+ that were defined in /boot/loader.conf
+ earlier. More information can be found in the &xen;
+ Documentation. NDomU guest VMs can now be
+ created.
+
+
+
+ &xen; DomU Guest VM Configuration
+
+ Unprivileged domains consist of a configuration file and
+ virtual or physical hard disks. Virtual disk storage for
+ the DomU can be files created by &man.truncate.1; or ZFS
+ volumes as described in .
+ In this example, a 20 GB volume is used. A VM is
+ created with the ZFS volume, a &os; ISO image, 1 GB of
+ RAM and two virtual CPUs. The ISO installation file is
+ retrieved with &man.fetch.1; and saved locally in a file
+ called freebsd.iso.
+
+ &prompt.root; fetch ftp://ftp.freebsd.org/pub/FreeBSD/releases/ISO-IMAGES/10.3/FreeBSD-10.3-RELEASE-amd64-bootonly.iso -o freebsd.iso
+
+ A ZFS volume of 20 GB called
+ xendisk0 is created to serve as the disk
+ space for the VM.
+
+ &prompt.root; zfs create -V20G -o volmode=dev zroot/xendisk0
+
+ The new DomU guest VM is defined in a file. Some specific
+ definitions like name, keymap, and VNC connection details are
+ also defined. The following freebsd.cfg
+ contains a minimum DomU configuration for this example:
+
+ &prompt.root; cat freebsd.cfg
+builder = "hvm"
+name = "freebsd"
+memory = 1024
+vcpus = 2
+vif = [ 'mac=00:16:3E:74:34:32,bridge=bridge0' ]
+disk = [
+'/dev/zvol/tank/xendisk0,raw,hda,rw',
+'/root/freebsd.iso,raw,hdc:cdrom,r'
+ ]
+vnc = 1
+vnclisten = "0.0.0.0"
+serial="pty"
+usbdevice="tablet"
+
+ These lines are explained in more detail:
+
+
+
+ This defines what kind of virtualization to use.
+ hvm refers to hardware-assisted
+ virtualization or hardware virtual machine. Guest
+ operating systems can run unmodified on CPUs with
+ virtualization extensions, providing nearly the same
+ performance as running on physical hardware.
+ generic is the default value and
+ creates a PV domain.
+
+
+
+ Name of this virtual machine to distinguish it from
+ others running on the same Dom0. Required.
+
+
+
+ Quantity of RAM in megabytes to make available to the
+ VM. This amount is subtracted from the hypervisor's total
+ available memory, not the memory of the Dom0.
+
+
+
+ Number of virtual CPUs available to the guest VM. For
+ best performance, do not create guests with more virtual
+ CPUs than the number of physical CPUs on the host.
+
+
+
+ Virtual network adapter. This is the bridge connected
+ to the network interface of the host. The
+ mac parameter is the MAC address set on
+ the virtual network interface. This parameter is
+ optional, if no MAC is provided &xen; will generate a
+ random one.
+
+
+
+ Full path to the disk, file, or ZFS volume of the disk
+ storage for this VM. Options and multiple disk
+ definitions are separated by commas.
+
+
+
+ Defines the Boot medium from which the initial
+ operating system is installed. In this example, it is the
+ ISO imaged downloaded earlier. Consult the &xen;
+ documentation for other kinds of devices and options to
+ set.
+
+
+
+ Options controlling VNC connectivity to the serial
+ console of the DomU. In order, these are: active VNC
+ support, define IP address on which to listen, device node
+ for the serial console, and the input method for precise
+ positioning of the mouse and other input methods.
+ keymap defines which keymap to use, and
+ is english by default.
+
+
+
+ After the file has been created with all the necessary
+ options, the DomU is created by passing it to xl
+ create as a parameter.
+
+ &prompt.root; xl create freebsd.cfg
+
+
+ Each time the Dom0 is restarted, the configuration file
+ must be passed to xl create again to
+ re-create the DomU. By default, only the Dom0 is created
+ after a reboot, not the individual VMs. The VMs can
+ continue where they left off as they stored the operating
+ system on the virtual disk. The virtual machine
+ configuration can change over time (for example, when adding
+ more memory). The virtual machine configuration files must
+ be properly backed up and kept available to be able to
+ re-create the guest VM when needed.
+
+
+ The output of xl list confirms that the
+ DomU has been created.
+
+ &prompt.root; xl list
+Name ID Mem VCPUs State Time(s)
+Domain-0 0 8192 4 r----- 1653.4
+freebsd 1 1024 1 -b---- 663.9
+
+ To begin the installation of the base operating system,
+ start the VNC client, directing it to the main network address
+ of the host or to the IP address defined on the
+ vnclisten line of
+ freebsd.cfg. After the operating system
+ has been installed, shut down the DomU and disconnect the VNC
+ viewer. Edit freebsd.cfg, removing the
+ line with the cdrom definition or
+ commenting it out by inserting a #
+ character at the beginning of the line. To load this new
+ configuration, it is necessary to remove the old DomU with
+ xl destroy, passing either the name or the
+ id as the parameter. Afterwards, recreate it using the
+ modified freebsd.cfg.
+
+ &prompt.root; xl destroy freebsd
+&prompt.root; xl create freebsd.cfg
+
+ The machine can then be accessed again using the VNC
+ viewer. This time, it will boot from the virtual disk where
+ the operating system has been installed and can be used as a
+ virtual machine.
+