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<h1>Domain XML format</h1>
<ul><li>
<a href="#elements">Element and attribute overview</a>
<ul><li>
<a href="#elementsMetadata">General metadata</a>
</li><li>
<a href="#elementsOS">Operating system booting</a>
<ul><li>
<a href="#elementsOSBIOS">BIOS bootloader</a>
</li><li>
<a href="#elementsOSBootloader">Host bootloader</a>
</li><li>
<a href="#elementsOSKernel">Direct kernel boot</a>
</li><li>
<a href="#eleemntsOSContainer">Container boot</a>
</li></ul>
</li><li>
<a href="#elementsSysinfo">SMBIOS System Information</a>
</li><li>
<a href="#elementsCPUAllocation">CPU Allocation</a>
</li><li>
<a href="#elementsCPUTuning">CPU Tuning</a>
</li><li>
<a href="#elementsMemoryAllocation">Memory Allocation</a>
</li><li>
<a href="#elementsMemoryBacking">Memory Backing</a>
</li><li>
<a href="#elementsMemoryTuning">Memory Tuning</a>
</li><li>
<a href="#elementsNUMATuning">NUMA Node Tuning</a>
</li><li>
<a href="#elementsBlockTuning">Block I/O Tuning</a>
</li><li>
<a href="#elementsCPU">CPU model and topology</a>
</li><li>
<a href="#elementsLifecycle">Lifecycle control</a>
</li><li>
<a href="#elementsFeatures">Hypervisor features</a>
</li><li>
<a href="#elementsTime">Time keeping</a>
</li><li>
<a href="#elementsDevices">Devices</a>
<ul><li>
<a href="#elementsDisks">Hard drives, floppy disks, CDROMs</a>
</li><li>
<a href="#elementsFilesystems">Filesystems</a>
</li><li>
<a href="#elementsAddress">Device Addresses</a>
</li><li>
<a href="#elementsControllers">Controllers</a>
</li><li>
<a href="#elementsLease">Device leases</a>
</li><li>
<a href="#elementsUSB">USB and PCI devices</a>
</li><li>
<a href="#elementsRedir">Redirected devices</a>
</li><li>
<a href="#elementsSmartcard">Smartcard devices</a>
</li><li>
<a href="#elementsNICS">Network interfaces</a>
<ul><li>
<a href="#elementsNICSVirtual">Virtual network</a>
</li><li>
<a href="#elementsNICSBridge">Bridge to LAN</a>
</li><li>
<a href="#elementsNICSSlirp">Userspace SLIRP stack</a>
</li><li>
<a href="#elementsNICSEthernet">Generic ethernet connection</a>
</li><li>
<a href="#elementsNICSDirect">Direct attachment to physical interface</a>
</li><li>
<a href="#elementsNICSHostdev">PCI Passthrough</a>
</li><li>
<a href="#elementsNICSMulticast">Multicast tunnel</a>
</li><li>
<a href="#elementsNICSTCP">TCP tunnel</a>
</li><li>
<a href="#elementsNICSModel">Setting the NIC model</a>
</li><li>
<a href="#elementsDriverBackendOptions">Setting NIC driver-specific options</a>
</li><li>
<a href="#elementsNICSTargetOverride">Overriding the target element</a>
</li><li>
<a href="#elementsNICSBoot">Specifying boot order</a>
</li><li>
<a href="#elementsNICSROM">Interface ROM BIOS configuration</a>
</li><li>
<a href="#elementQoS">Quality of service</a>
</li><li>
<a href="#elementLink">Modifying virtual link state</a>
</li></ul>
</li><li>
<a href="#elementsInput">Input devices</a>
</li><li>
<a href="#elementsHub">Hub devices</a>
</li><li>
<a href="#elementsGraphics">Graphical framebuffers</a>
</li><li>
<a href="#elementsVideo">Video devices</a>
</li><li>
<a href="#elementsConsole">Consoles, serial, parallel & channel devices</a>
<ul><li>
<a href="#elementsCharGuestInterface">Guest interface</a>
<ul><li>
<a href="#elementCharParallel">Parallel port</a>
</li><li>
<a href="#elementCharSerial">Serial port</a>
</li><li>
<a href="#elementCharConsole">Console</a>
</li><li>
<a href="#elementCharChannel">Channel</a>
</li></ul>
</li><li>
<a href="#elementsCharHostInterface">Host interface</a>
<ul><li>
<a href="#elementsCharSTDIO">Domain logfile</a>
</li><li>
<a href="#elementsCharFle">Device logfile</a>
</li><li>
<a href="#elementsCharVC">Virtual console</a>
</li><li>
<a href="#elementsCharNull">Null device</a>
</li><li>
<a href="#elementsCharPTY">Pseudo TTY</a>
</li><li>
<a href="#elementsCharHost">Host device proxy</a>
</li><li>
<a href="#elementsCharPipe">Named pipe</a>
</li><li>
<a href="#elementsCharTCP">TCP client/server</a>
</li><li>
<a href="#elementsCharUDP">UDP network console</a>
</li><li>
<a href="#elementsCharUNIX">UNIX domain socket client/server</a>
</li></ul>
</li></ul>
</li><li>
<a href="#elementsSound">Sound devices</a>
</li><li>
<a href="#elementsWatchdog">Watchdog device</a>
</li><li>
<a href="#elementsMemBalloon">Memory balloon device</a>
</li></ul>
</li><li>
<a href="#seclabel">Security label</a>
</li></ul>
</li><li>
<a href="#examples">Example configs</a>
</li></ul>
<p>
This section describes the XML format used to represent domains, there are
variations on the format based on the kind of domains run and the options
used to launch them. For hypervisor specific details consult the
<a href="drivers.html">driver docs</a>
</p>
<h2>
<a name="elements" id="elements">Element and attribute overview</a>
</h2>
<p>
The root element required for all virtual machines is
named <code>domain</code>. It has two attributes, the
<code>type</code> specifies the hypervisor used for running
the domain. The allowed values are driver specific, but
include "xen", "kvm", "qemu", "lxc" and "kqemu". The
second attribute is <code>id</code> which is a unique
integer identifier for the running guest machine. Inactive
machines have no id value.
</p>
<h3>
<a name="elementsMetadata" id="elementsMetadata">General metadata</a>
</h3>
<pre>
<domain type='xen' id='3'>
<name>fv0</name>
<uuid>4dea22b31d52d8f32516782e98ab3fa0</uuid>
<title>A short description - title - of the domain</title>
<description>Some human readable description</description>
<metadata>
<app1:foo xmlns:app1="http://app1.org/app1/">..</app1:foo>
<app2:bar xmlns:app2="http://app1.org/app2/">..</app2:bar>
</metadata>
...</pre>
<dl><dt><code>name</code></dt><dd>The content of the <code>name</code> element provides
a short name for the virtual machine. This name should
consist only of alpha-numeric characters and is required
to be unique within the scope of a single host. It is
often used to form the filename for storing the persistent
configuration file. <span class="since">Since 0.0.1</span></dd><dt><code>uuid</code></dt><dd>The content of the <code>uuid</code> element provides
a globally unique identifier for the virtual machine.
The format must be RFC 4122 compliant,
eg <code>3e3fce45-4f53-4fa7-bb32-11f34168b82b</code>.
If omitted when defining/creating a new machine, a random
UUID is generated. It is also possible to provide the UUID
via a <a href="#elementsSysinfo"><code>sysinfo</code></a>
specification. <span class="since">Since 0.0.1, sysinfo
since 0.8.7</span></dd><dt><code>title</code></dt><dd>The optional element <code>title</code> provides space for a
short description of the domain. The title should not contain
any newlines. <span class="since">Since 0.9.10</span>.</dd><dt><code>description</code></dt><dd>The content of the <code>description</code> element provides a
human readable description of the virtual machine. This data is not
used by libvirt in any way, it can contain any information the user
wants. <span class="since">Since 0.7.2</span></dd><dt><code>metadata</code></dt><dd>The <code>metadata</code> node can be used by applications
to store custom metadata in the form of XML
nodes/trees. Applications must use custom namespaces on their
XML nodes/trees, with only one top-level element per namespace
(if the application needs structure, they should have
sub-elements to their namespace
element). <span class="since">Since 0.9.10</span></dd></dl>
<h3>
<a name="elementsOS" id="elementsOS">Operating system booting</a>
</h3>
<p>
There are a number of different ways to boot virtual machines
each with their own pros and cons.
</p>
<h4>
<a name="elementsOSBIOS" id="elementsOSBIOS">BIOS bootloader</a>
</h4>
<p>
Booting via the BIOS is available for hypervisors supporting
full virtualization. In this case the BIOS has a boot order
priority (floppy, harddisk, cdrom, network) determining where
to obtain/find the boot image.
</p>
<pre>
...
<os>
<type>hvm</type>
<loader>/usr/lib/xen/boot/hvmloader</loader>
<boot dev='hd'/>
<boot dev='cdrom'/>
<bootmenu enable='yes'/>
<smbios mode='sysinfo'/>
<bios useserial='yes'/>
</os>
...</pre>
<dl><dt><code>type</code></dt><dd>The content of the <code>type</code> element specifies the
type of operating system to be booted in the virtual machine.
<code>hvm</code> indicates that the OS is one designed to run
on bare metal, so requires full virtualization. <code>linux</code>
(badly named!) refers to an OS that supports the Xen 3 hypervisor
guest ABI. There are also two optional attributes, <code>arch</code>
specifying the CPU architecture to virtualization,
and <code>machine</code> referring to the machine
type. The <a href="formatcaps.html">Capabilities XML</a>
provides details on allowed values for
these. <span class="since">Since 0.0.1</span></dd><dt><code>loader</code></dt><dd>The optional <code>loader</code> tag refers to a firmware blob
used to assist the domain creation process. At this time, it is
only needed by Xen fully virtualized
domains. <span class="since">Since 0.1.0</span></dd><dt><code>boot</code></dt><dd>The <code>dev</code> attribute takes one of the values "fd", "hd",
"cdrom" or "network" and is used to specify the next boot device
to consider. The <code>boot</code> element can be repeated multiple
times to setup a priority list of boot devices to try in turn.
Multiple devices of the same type are sorted according to their
targets while preserving the order of buses. After defining the
domain, its XML configuration returned by libvirt (through
virDomainGetXMLDesc) lists devices in the sorted order. Once sorted,
the first device is marked as bootable. Thus, e.g., a domain
configured to boot from "hd" with vdb, hda, vda, and hdc disks
assigned to it will boot from vda (the sorted list is vda, vdb, hda,
hdc). Similar domain with hdc, vda, vdb, and hda disks will boot from
hda (sorted disks are: hda, hdc, vda, vdb). It can be tricky to
configure in the desired way, which is why per-device boot elements
(see <a href="#elementsDisks">disks</a>,
<a href="#elementsNICS">network interfaces</a>, and
<a href="#elementsUSB">USB and PCI devices</a> sections below) were
introduced and they are the preferred way providing full control over
booting order. The <code>boot</code> element and per-device boot
elements are mutually exclusive. <span class="since">Since 0.1.3,
per-device boot since 0.8.8</span>
</dd><dt><code>bootmenu</code></dt><dd> Whether or not to enable an interactive boot menu prompt on guest
startup. The <code>enable</code> attribute can be either "yes" or "no".
If not specified, the hypervisor default is used. <span class="since">
Since 0.8.3</span>
</dd><dt><code>smbios</code></dt><dd>How to populate SMBIOS information visible in the guest.
The <code>mode</code> attribute must be specified, and is either
"emulate" (let the hypervisor generate all values), "host" (copy
all of Block 0 and Block 1, except for the UUID, from the host's
SMBIOS values;
the <a href="html/libvirt-libvirt.html#virConnectGetSysinfo">
<code>virConnectGetSysinfo</code></a> call can be
used to see what values are copied), or "sysinfo" (use the values in
the <a href="#elementsSysinfo">sysinfo</a> element). If not
specified, the hypervisor default is used. <span class="since">
Since 0.8.7</span>
</dd><dt><code>bios</code></dt><dd>This element has attribute <code>useserial</code> with possible
values <code>yes</code> or <code>no</code>. It enables or disables
Serial Graphics Adapter which allows users to see BIOS messages
on a serial port. Therefore, one needs to have
<a href="#elementCharSerial">serial port</a> defined.
<span class="since">Since 0.9.4</span>
</dd></dl>
<h4>
<a name="elementsOSBootloader" id="elementsOSBootloader">Host bootloader</a>
</h4>
<p>
Hypervisors employing paravirtualization do not usually emulate
a BIOS, and instead the host is responsible to kicking off the
operating system boot. This may use a pseudo-bootloader in the
host to provide an interface to choose a kernel for the guest.
An example is <code>pygrub</code> with Xen.
</p>
<pre>
...
<bootloader>/usr/bin/pygrub</bootloader>
<bootloader_args>--append single</bootloader_args>
...</pre>
<dl><dt><code>bootloader</code></dt><dd>The content of the <code>bootloader</code> element provides
a fully qualified path to the bootloader executable in the
host OS. This bootloader will be run to choose which kernel
to boot. The required output of the bootloader is dependent
on the hypervisor in use. <span class="since">Since 0.1.0</span></dd><dt><code>bootloader_args</code></dt><dd>The optional <code>bootloader_args</code> element allows
command line arguments to be passed to the bootloader.
<span class="since">Since 0.2.3</span>
</dd></dl>
<h4>
<a name="elementsOSKernel" id="elementsOSKernel">Direct kernel boot</a>
</h4>
<p>
When installing a new guest OS it is often useful to boot directly
from a kernel and initrd stored in the host OS, allowing command
line arguments to be passed directly to the installer. This capability
is usually available for both para and full virtualized guests.
</p>
<pre>
...
<os>
<type>hvm</type>
<loader>/usr/lib/xen/boot/hvmloader</loader>
<kernel>/root/f8-i386-vmlinuz</kernel>
<initrd>/root/f8-i386-initrd</initrd>
<cmdline>console=ttyS0 ks=http://example.com/f8-i386/os/</cmdline>
</os>
...</pre>
<dl><dt><code>type</code></dt><dd>This element has the same semantics as described earlier in the
<a href="#elementsOSBIOS">BIOS boot section</a></dd><dt><code>loader</code></dt><dd>This element has the same semantics as described earlier in the
<a href="#elementsOSBIOS">BIOS boot section</a></dd><dt><code>kernel</code></dt><dd>The contents of this element specify the fully-qualified path
to the kernel image in the host OS.</dd><dt><code>initrd</code></dt><dd>The contents of this element specify the fully-qualified path
to the (optional) ramdisk image in the host OS.</dd><dt><code>cmdline</code></dt><dd>The contents of this element specify arguments to be passed to
the kernel (or installer) at boottime. This is often used to
specify an alternate primary console (eg serial port), or the
installation media source / kickstart file</dd></dl>
<h4>
<a name="eleemntsOSContainer" id="eleemntsOSContainer">Container boot</a>
</h4>
<p>
When booting a domain using container based virtualization, instead
of a kernel / boot image, a path to the init binary is required, using
the <code>init</code> element. By default this will be launched with
no arguments. To specify the initial argv, use the <code>initarg</code>
element, repeated as many time as is required. The <code>cmdline</code>
element, if set will be used to provide an equivalent to <code>/proc/cmdline</code>
but will not effect init argv.
</p>
<pre>
<os>
<type arch='x86_64'>exe</type>
<init>/bin/systemd</init>
<initarg>--unit</initarg>
<initarg>emergency.service</initarg>
</os>
</pre>
<h3>
<a name="elementsSysinfo" id="elementsSysinfo">SMBIOS System Information</a>
</h3>
<p>
Some hypervisors allow control over what system information is
presented to the guest (for example, SMBIOS fields can be
populated by a hypervisor and inspected via
the <code>dmidecode</code> command in the guest). The
optional <code>sysinfo</code> element covers all such categories
of information. <span class="since">Since 0.8.7</span>
</p>
<pre>
...
<os>
<smbios mode='sysinfo'/>
...
</os>
<sysinfo type='smbios'>
<bios>
<entry name='vendor'>LENOVO</entry>
</bios>
<system>
<entry name='manufacturer'>Fedora</entry>
<entry name='vendor'>Virt-Manager</entry>
</system>
</sysinfo>
...</pre>
<p>
The <code>sysinfo</code> element has a mandatory
attribute <code>type</code> that determine the layout of
sub-elements, with supported values of:
</p>
<dl><dt><code>smbios</code></dt><dd>Sub-elements call out specific SMBIOS values, which will
affect the guest if used in conjunction with
the <code>smbios</code> sub-element of
the <a href="#elementsOS"><code>os</code></a> element. Each
sub-element of <code>sysinfo</code> names a SMBIOS block, and
within those elements can be a list of <code>entry</code>
elements that describe a field within the block. The following
blocks and entries are recognized:
<dl><dt><code>bios</code></dt><dd>
This is block 0 of SMBIOS, with entry names drawn from
"vendor", "version", "date", and "release".
</dd><dt><code>system</code></dt><dd>
This is block 1 of SMBIOS, with entry names drawn from
"manufacturer", "product", "version", "serial", "uuid",
"sku", and "family". If a "uuid" entry is provided
alongside a
top-level <a href="#elementsMetadata"><code>uuid</code>
element</a>, the two values must match.
</dd></dl></dd></dl>
<h3>
<a name="elementsCPUAllocation" id="elementsCPUAllocation">CPU Allocation</a>
</h3>
<pre>
<domain>
...
<vcpu placement='static' cpuset="1-4,^3,6" current="1">2</vcpu>
...
</domain>
</pre>
<dl><dt><code>vcpu</code></dt><dd>The content of this element defines the maximum number of virtual
CPUs allocated for the guest OS, which must be between 1 and
the maximum supported by the hypervisor. <span class="since">Since
0.4.4</span>, this element can contain an optional
<code>cpuset</code> attribute, which is a comma-separated
list of physical CPU numbers that virtual CPUs can be pinned
to. Each element in that list is either a single CPU number,
a range of CPU numbers, or a caret followed by a CPU number to
be excluded from a previous range. <span class="since">Since
0.8.5</span>, the optional attribute <code>current</code> can
be used to specify whether fewer than the maximum number of
virtual CPUs should be enabled. <span class="since">Since
0.9.11 (QEMU and KVM only)</span>, the optional attribute
<code>placement</code> can be used to indicate the CPU placement
mode for domain process, its value can be either "static" or
"auto", defaults to "static" if <code>cpuset</code> is specified,
"auto" indicates the domain process will be pinned to the advisory
nodeset from querying numad, and the value of attribute
<code>cpuset</code> will be ignored if it's specified. If both
<code>cpuset</code> and <code>placement</code> are not specified,
or if <code>placement</code> is "static", but no <code>cpuset</code>
is specified, the domain process will be pinned to all the
available physical CPUs.
</dd></dl>
<h3>
<a name="elementsCPUTuning" id="elementsCPUTuning">CPU Tuning</a>
</h3>
<pre>
<domain>
...
<cputune>
<vcpupin vcpu="0" cpuset="1-4,^2"/>
<vcpupin vcpu="1" cpuset="0,1"/>
<vcpupin vcpu="2" cpuset="2,3"/>
<vcpupin vcpu="3" cpuset="0,4"/>
<shares>2048</shares>
<period>1000000</period>
<quota>-1</quota>
</cputune>
...
</domain>
</pre>
<dl><dt><code>cputune</code></dt><dd>
The optional <code>cputune</code> element provides details
regarding the cpu tunable parameters for the domain.
<span class="since">Since 0.9.0</span>
</dd><dt><code>vcpupin</code></dt><dd>
The optional <code>vcpupin</code> element specifies which of host
physical CPUS the domain VCPU will be pinned to. If this is omitted,
each VCPU is pinned to all the physical CPUS by default. It contains two
required attributes, the attribute <code>vcpu</code> specifies vcpu id,
and the attribute <code>cpuset</code> is same as
attribute <code>cpuset</code>
of element <code>vcpu</code>. (NB: Only qemu driver support)
<span class="since">Since 0.9.0</span>
</dd><dt><code>shares</code></dt><dd>
The optional <code>shares</code> element specifies the proportional
weighted share for the domain. If this is omitted, it defaults to
the OS provided defaults. NB, There is no unit for the value,
it's a relative measure based on the setting of other VM,
e.g. A VM configured with value
2048 will get twice as much CPU time as a VM configured with value 1024.
<span class="since">Since 0.9.0</span>
</dd><dt><code>period</code></dt><dd>
The optional <code>period</code> element specifies the enforcement
interval(unit: microseconds). Within <code>period</code>, each vcpu of
the domain will not be allowed to consume more than <code>quota</code>
worth of runtime. The value should be in range [1000, 1000000]. A period
with value 0 means no value. (NB: Only qemu driver support)
<span class="since">Since 0.9.4</span>
</dd><dt><code>quota</code></dt><dd>
The optional <code>quota</code> element specifies the maximum allowed
bandwidth(unit: microseconds). A domain with <code>quota</code> as any
negative value indicates that the domain has infinite bandwidth, which
means that it is not bandwidth controlled. The value should be in range
[1000, 18446744073709551] or less than 0. A quota with value 0 means no
value. You can use this feature to ensure that all vcpus run at the same
speed. (NB: Only qemu driver support)
<span class="since">Since 0.9.4</span>
</dd></dl>
<h3>
<a name="elementsMemoryAllocation" id="elementsMemoryAllocation">Memory Allocation</a>
</h3>
<pre>
<domain>
...
<memory unit='KiB'>524288</memory>
<currentMemory unit='KiB'>524288</currentMemory>
...
</domain>
</pre>
<dl><dt><code>memory</code></dt><dd>The maximum allocation of memory for the guest at boot time.
The units for this value are determined by the optional
atttribute <code>unit</code>, which defaults to "KiB"
(kibibytes, 2<sup>10</sup> or blocks of 1024 bytes). Valid
units are "b" or "bytes" for bytes, "KB" for kilobytes
(10<sup>3</sup> or 1,000 bytes), "k" or "KiB" for kibibytes
(1024 bytes), "MB" for megabytes (10<sup>6</sup> or 1,000,000
bytes), "M" or "MiB" for mebibytes (2<sup>20</sup> or
1,048,576 bytes), "GB" for gigabytes (10<sup>9</sup> or
1,000,000,000 bytes), "G" or "GiB" for gibibytes
(2<sup>30</sup> or 1,073,741,824 bytes), "TB" for terabytes
(10<sup>12</sup> or 1,000,000,000,000 bytes), or "T" or "TiB"
for tebibytes (2<sup>40</sup> or 1,099,511,627,776 bytes).
However, the value will be rounded up to the nearest kibibyte
by libvirt, and may be further rounded to the granularity
supported by the hypervisor. Some hypervisors also enforce a
minimum, such as
4000KiB. <span class="since"><code>unit</code> since
0.9.11</span></dd><dt><code>currentMemory</code></dt><dd>The actual allocation of memory for the guest. This value can
be less than the maximum allocation, to allow for ballooning
up the guests memory on the fly. If this is omitted, it defaults
to the same value as the <code>memory</code> element.
The <code>unit</code> attribute behaves the same as
for <code>memory</code>.</dd></dl>
<h3>
<a name="elementsMemoryBacking" id="elementsMemoryBacking">Memory Backing</a>
</h3>
<pre>
<domain>
...
<memoryBacking>
<hugepages/>
</memoryBacking>
...
</domain>
</pre>
<dl><dt><code>memoryBacking</code></dt><dd>The optional <code>memoryBacking</code> element, may have an
<code>hugepages</code> element set within it. This tells the
hypervisor that the guest should have its memory allocated using
hugepages instead of the normal native page size.</dd></dl>
<h3>
<a name="elementsMemoryTuning" id="elementsMemoryTuning">Memory Tuning</a>
</h3>
<pre>
<domain>
...
<memtune>
<hard_limit unit='G'>1</hard_limit>
<soft_limit unit='M'>128</soft_limit>
<swap_hard_limit unit='G'>2</swap_hard_limit>
<min_guarantee unit='bytes'>67108864</min_guarantee>
</memtune>
...
</domain>
</pre>
<dl><dt><code>memtune</code></dt><dd> The optional <code>memtune</code> element provides details
regarding the memory tunable parameters for the domain. If this is
omitted, it defaults to the OS provided defaults. For QEMU/KVM, the
parameters are applied to the QEMU process as a whole. Thus, when
counting them, one needs to add up guest RAM, guest video RAM, and
some memory overhead of QEMU itself. The last piece is hard to
determine so one needs guess and try. For each tunable, it
is possible to designate which unit the number is in on
input, using the same values as
for <code><memory></code>. For backwards
compatibility, output is always in
KiB. <span class="since"><code>unit</code>
since 0.9.11</span></dd><dt><code>hard_limit</code></dt><dd> The optional <code>hard_limit</code> element is the maximum memory
the guest can use. The units for this value are kibibytes (i.e. blocks
of 1024 bytes)</dd><dt><code>soft_limit</code></dt><dd> The optional <code>soft_limit</code> element is the memory limit to
enforce during memory contention. The units for this value are
kibibytes (i.e. blocks of 1024 bytes)</dd><dt><code>swap_hard_limit</code></dt><dd> The optional <code>swap_hard_limit</code> element is the maximum
memory plus swap the guest can use. The units for this value are
kibibytes (i.e. blocks of 1024 bytes). This has to be more than
hard_limit value provided</dd><dt><code>min_guarantee</code></dt><dd> The optional <code>min_guarantee</code> element is the guaranteed
minimum memory allocation for the guest. The units for this value are
kibibytes (i.e. blocks of 1024 bytes)</dd></dl>
<h3>
<a name="elementsNUMATuning" id="elementsNUMATuning">NUMA Node Tuning</a>
</h3>
<pre>
<domain>
...
<numatune>
<memory mode="strict" nodeset="1-4,^3"/>
</numatune>
...
</domain>
</pre>
<dl><dt><code>numatune</code></dt><dd>
The optional <code>numatune</code> element provides details of
how to tune the performance of a NUMA host via controlling NUMA policy
for domain process. NB, only supported by QEMU driver.
<span class="since">Since 0.9.3</span>
</dd><dt><code>memory</code></dt><dd>
The optional <code>memory</code> element specifies how to allocate memory
for the domain process on a NUMA host. It contains two attributes,
attribute <code>mode</code> is either 'interleave', 'strict',
or 'preferred',
attribute <code>nodeset</code> specifies the NUMA nodes, it leads same
syntax with attribute <code>cpuset</code> of element <code>vcpu</code>.
<span class="since">Since 0.9.3</span>
</dd></dl>
<h3>
<a name="elementsBlockTuning" id="elementsBlockTuning">Block I/O Tuning</a>
</h3>
<pre>
<domain>
...
<blkiotune>
<weight>800</weight>
<device>
<path>/dev/sda</path>
<weight>1000</weight>
</device>
<device>
<path>/dev/sdb</path>
<weight>500</weight>
</device>
</blkiotune>
...
</domain>
</pre>
<dl><dt><code>blkiotune</code></dt><dd> The optional <code>blkiotune</code> element provides the ability
to tune Blkio cgroup tunable parameters for the domain. If this is
omitted, it defaults to the OS provided
defaults. <span class="since">Since 0.8.8</span></dd><dt><code>weight</code></dt><dd> The optional <code>weight</code> element is the overall I/O
weight of the guest. The value should be in the range [100,
1000].</dd><dt><code>device</code></dt><dd>The domain may have multiple <code>device</code> elements
that further tune the weights for each host block device in
use by the domain. Note that
multiple <a href="#elementsDisks">guest disks</a> can share a
single host block device, if they are backed by files within
the same host file system, which is why this tuning parameter
is at the global domain level rather than associated with each
guest disk device (contrast this to
the <a href="#elementsDisks"><code><iotune></code></a>
element which can apply to an
individual <code><disk></code>).
Each <code>device</code> element has two
mandatory sub-elements, <code>path</code> describing the
absolute path of the device, and <code>weight</code> giving
the relative weight of that device, in the range [100,
1000]. <span class="since">Since 0.9.8</span></dd></dl>
<h3>
<a name="elementsCPU" id="elementsCPU">CPU model and topology</a>
</h3>
<p>
Requirements for CPU model, its features and topology can be specified
using the following collection of elements.
<span class="since">Since 0.7.5</span>
</p>
<pre>
...
<cpu match='exact'>
<model fallback='allow'>core2duo</model>
<vendor>Intel</vendor>
<topology sockets='1' cores='2' threads='1'/>
<feature policy='disable' name='lahf_lm'/>
</cpu>
...</pre>
<pre>
<cpu mode='host-model'>
<model fallback='forbid'/>
<topology sockets='1' cores='2' threads='1'/>
</cpu>
...</pre>
<pre>
<cpu mode='host-passthrough'/>
...</pre>
<p>
In case no restrictions need to be put on CPU model and its features, a
simpler <code>cpu</code> element can be used.
<span class="since">Since 0.7.6</span>
</p>
<pre>
...
<cpu>
<topology sockets='1' cores='2' threads='1'/>
</cpu>
...</pre>
<dl><dt><code>cpu</code></dt><dd>The <code>cpu</code> element is the main container for describing
guest CPU requirements. Its <code>match</code> attribute specified how
strictly has the virtual CPU provided to the guest match these
requirements. <span class="since">Since 0.7.6</span> the
<code>match</code> attribute can be omitted if <code>topology</code>
is the only element within <code>cpu</code>. Possible values for the
<code>match</code> attribute are:
<dl><dt><code>minimum</code></dt><dd>The specified CPU model and features describes the minimum
requested CPU.</dd><dt><code>exact</code></dt><dd>The virtual CPU provided to the guest will exactly match the
specification</dd><dt><code>strict</code></dt><dd>The guest will not be created unless the host CPU does exactly
match the specification.</dd></dl><span class="since">Since 0.8.5</span> the <code>match</code>
attribute can be omitted and will default to <code>exact</code>.
<span class="since">Since 0.9.10</span>, an optional <code>mode</code>
attribute may be used to make it easier to configure a guest CPU to be
as close to host CPU as possible. Possible values for the
<code>mode</code> attribute are:
<dl><dt><code>custom</code></dt><dd>In this mode, the <code>cpu</code> element describes the CPU
that should be presented to the guest. This is the default when no
<code>mode</code> attribute is specified. This mode makes it so that
a persistent guest will see the same hardware no matter what host
the guest is booted on.</dd><dt><code>host-model</code></dt><dd>The <code>host-model</code> mode is essentially a shortcut to
copying host CPU definition from capabilities XML into domain XML.
Since the CPU definition is copied just before starting a domain,
exactly the same XML can be used on different hosts while still
providing the best guest CPU each host supports. Neither
<code>match</code> attribute nor any <code>feature</code> elements
can be used in this mode. Specifying CPU model is not supported
either, but <code>model</code>'s <code>fallback</code> attribute may
still be used. Libvirt does not model every aspect of each CPU so
the guest CPU will not match the host CPU exactly. On the other
hand, the ABI provided to the guest is reproducible. During
migration, complete CPU model definition is transferred to the
destination host so the migrated guest will see exactly the same CPU
model even if the destination host contains more capable CPUs for
the running instance of the guest; but shutting down and restarting
the guest may present different hardware to the guest according to
the capabilities of the new host.</dd><dt><code>host-passthrough</code></dt><dd>With this mode, the CPU visible to the guest should be exactly
the same as the host CPU even in the aspects that libvirt does not
understand. Though the downside of this mode is that the guest
environment cannot be reproduced on different hardware. Thus, if you
hit any bugs, you are on your own. Neither <code>model</code> nor
<code>feature</code> elements are allowed in this mode.</dd></dl>
In both <code>host-model</code> and <code>host-passthrough</code>
mode, the real (approximate in <code>host-passthrough</code> mode) CPU
definition which would be used on current host can be determined by
specifying <code>VIR_DOMAIN_XML_UPDATE_CPU</code> flag when calling
<code>virDomainGetXMLDesc</code> API. When running a guest that might
be prone to operating system reactivation when presented with
different hardware, and which will be migrated between hosts with
different capabilities, you can use this output to rewrite XML to the
<code>custom</code> mode for more robust migration.
</dd><dt><code>model</code></dt><dd>The content of the <code>model</code> element specifies CPU model
requested by the guest. The list of available CPU models and their
definition can be found in <code>cpu_map.xml</code> file installed
in libvirt's data directory. If a hypervisor is not able to use the
exact CPU model, libvirt automatically falls back to a closest model
supported by the hypervisor while maintaining the list of CPU
features. <span class="since">Since 0.9.10</span>, an optional
<code>fallback</code> attribute can be used to forbid this behavior,
in which case an attempt to start a domain requesting an unsupported
CPU model will fail. Supported values for <code>fallback</code>
attribute are: <code>allow</code> (this is the default), and
<code>forbid</code>.</dd><dt><code>vendor</code></dt><dd><span class="since">Since 0.8.3</span> the content of the
<code>vendor</code> element specifies CPU vendor requested by the
guest. If this element is missing, the guest can be run on a CPU
matching given features regardless on its vendor. The list of
supported vendors can be found in <code>cpu_map.xml</code>.</dd><dt><code>topology</code></dt><dd>The <code>topology</code> element specifies requested topology of
virtual CPU provided to the guest. Three non-zero values have to be
given for <code>sockets</code>, <code>cores</code>, and
<code>threads</code>: total number of CPU sockets, number of cores per
socket, and number of threads per core, respectively.</dd><dt><code>feature</code></dt><dd>The <code>cpu</code> element can contain zero or more
<code>elements</code> used to fine-tune features provided by the
selected CPU model. The list of known feature names can be found in
the same file as CPU models. The meaning of each <code>feature</code>
element depends on its <code>policy</code> attribute, which has to be
set to one of the following values:
<dl><dt><code>force</code></dt><dd>The virtual CPU will claim the feature is supported regardless
of it being supported by host CPU.</dd><dt><code>require</code></dt><dd>Guest creation will fail unless the feature is supported by host
CPU.</dd><dt><code>optional</code></dt><dd>The feature will be supported by virtual CPU if and only if it
is supported by host CPU.</dd><dt><code>disable</code></dt><dd>The feature will not be supported by virtual CPU.</dd><dt><code>forbid</code></dt><dd>Guest creation will fail if the feature is supported by host
CPU.</dd></dl><span class="since">Since 0.8.5</span> the <code>policy</code>
attribute can be omitted and will default to <code>require</code>.
</dd></dl>
<p>
Guest NUMA topology can be specifed using the <code>numa</code> element.
<span class="since">Since 0.9.8</span>
</p>
<pre>
...
<cpu>
...
<numa>
<cell cpus='0-3' memory='512000'/>
<cell cpus='4-7' memory='512000'/>
</numa>
...
</cpu>
...</pre>
<p>
Each <code>cell</code> element specifies a NUMA cell or a NUMA node.
<code>cpus</code> specifies the CPU or range of CPUs that are part of
the node. <code>memory</code> specifies the node memory in kibibytes
(i.e. blocks of 1024 bytes). Each cell or node is assigned cellid
or nodeid in the increasing order starting from 0.
</p>
<p>
This guest NUMA specification is currently available only for QEMU/KVM.
</p>
<h3>
<a name="elementsLifecycle" id="elementsLifecycle">Lifecycle control</a>
</h3>
<p>
It is sometimes necessary to override the default actions taken
when a guest OS triggers a lifecycle operation. The following
collections of elements allow the actions to be specified. A
common use case is to force a reboot to be treated as a poweroff
when doing the initial OS installation. This allows the VM to be
re-configured for the first post-install bootup.
</p>
<pre>
...
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
...</pre>
<dl><dt><code>on_poweroff</code></dt><dd>The content of this element specifies the action to take when
the guest requests a poweroff.</dd><dt><code>on_reboot</code></dt><dd>The content of this element specifies the action to take when
the guest requests a reboot.</dd><dt><code>on_crash</code></dt><dd>The content of this element specifies the action to take when
the guest crashes.</dd></dl>
<p>
Each of these states allow for the same four possible actions.
</p>
<dl><dt><code>destroy</code></dt><dd>The domain will be terminated completely and all resources
released</dd><dt><code>restart</code></dt><dd>The domain will be terminated, and then restarted with
the same configuration</dd><dt><code>preserve</code></dt><dd>The domain will be terminated, and its resource preserved
to allow analysis.</dd><dt><code>rename-restart</code></dt><dd>The domain will be terminated, and then restarted with
a new name</dd></dl>
<p>
on_crash supports these additional
actions <span class="since">since 0.8.4</span>.
</p>
<dl><dt><code>coredump-destroy</code></dt><dd>The crashed domain's core will be dumped, and then the
domain will be terminated completely and all resources
released</dd><dt><code>coredump-restart</code></dt><dd>The crashed domain's core will be dumped, and then the
domain will be restarted with the same configuration</dd></dl>
<h3>
<a name="elementsFeatures" id="elementsFeatures">Hypervisor features</a>
</h3>
<p>
Hypervisors may allow certain CPU / machine features to be
toggled on/off.
</p>
<pre>
...
<features>
<pae/>
<acpi/>
<apic/>
<hap/>
<privnet/>
</features>
...</pre>
<p>
All features are listed within the <code>features</code>
element, omitting a togglable feature tag turns it off.
The available features can be found by asking
for the <a href="formatcaps.html">capabilities XML</a>,
but a common set for fully virtualized domains are:
</p>
<dl><dt><code>pae</code></dt><dd>Physical address extension mode allows 32-bit guests
to address more than 4 GB of memory.</dd><dt><code>acpi</code></dt><dd>ACPI is useful for power management, for example, with
KVM guests it is required for graceful shutdown to work.
</dd><dt><code>hap</code></dt><dd>Enable use of Hardware Assisted Paging if available in
the hardware.
</dd><dt><code>viridian</code></dt><dd>Enable Viridian hypervisor extensions for paravirtualizing
guest operating systems
</dd><dt><code>privnet</code></dt><dd>Always create a private network namespace. This is
automatically set if any interface devices are defined.
This feature is only relevant for container based
virtualization drivers, such as LXC.
</dd></dl>
<h3>
<a name="elementsTime" id="elementsTime">Time keeping</a>
</h3>
<p>
The guest clock is typically initialized from the host clock.
Most operating systems expect the hardware clock to be kept
in UTC, and this is the default. Windows, however, expects
it to be in so called 'localtime'.
</p>
<pre>
...
<clock offset='localtime'>
<timer name='rtc' tickpolicy='catchup' track='guest'>
<catchup threshold='123' slew='120' limit='10000'/>
</timer>
<timer name='pit' tickpolicy='delay'/>
</clock>
...</pre>
<dl><dt><code>clock</code></dt><dd>
<p>The <code>offset</code> attribute takes four possible
values, allowing fine grained control over how the guest
clock is synchronized to the host. NB, not all hypervisors
support all modes.</p>
<dl><dt><code>utc</code></dt><dd>
The guest clock will always be synchronized to UTC when
booted.
<span class="since">Since 0.9.11</span> 'utc' mode can be converted
to 'variable' mode, which can be controlled by using the
<code>adjustment</code> attribute. If the value is 'reset', the
conversion is never done (not all hypervisors can
synchronize to UTC on each boot; use of 'reset' will cause
an error on those hypervisors). A numeric value
forces the conversion to 'variable' mode using the value as the
initial adjustment. The default <code>adjustment</code> is
hypervisor specific.
</dd><dt><code>localtime</code></dt><dd>
The guest clock will be synchronized to the host's configured
timezone when booted, if any.
<span class="since">Since 0.9.11,</span> the <code>adjustment</code>
attribute behaves the same as in 'utc' mode.
</dd><dt><code>timezone</code></dt><dd>
The guest clock will be synchronized to the requested timezone
using the <code>timezone</code> attribute.
<span class="since">Since 0.7.7</span>
</dd><dt><code>variable</code></dt><dd>
The guest clock will have an arbitrary offset applied
relative to UTC or localtime, depending on the <code>basis</code>
attribute. The delta relative to UTC (or localtime) is specified
in seconds, using the <code>adjustment</code> attribute.
The guest is free to adjust the RTC over time and expect
that it will be honored at next reboot. This is in
contrast to 'utc' and 'localtime' mode (with the optional
attribute adjustment='reset'), where the RTC adjustments are
lost at each reboot. <span class="since">Since 0.7.7</span>
<span class="since">Since 0.9.11</span> the <code>basis</code>
attribute can be either 'utc' (default) or 'localtime'.
</dd></dl><p>
A <code>clock</code> may have zero or more
<code>timer</code>sub-elements. <span class="since">Since
0.8.0</span>
</p>
</dd><dt><code>timer</code></dt><dd>
<p>
Each timer element requires a <code>name</code> attribute,
and has other optional attributes that depend on
the <code>name</code> specified. Various hypervisors
support different combinations of attributes.
</p>
<dl><dt><code>name</code></dt><dd>
The <code>name</code> attribute selects which timer is
being modified, and can be one of "platform", "hpet",
"kvmclock", "pit", "rtc", or "tsc".
</dd><dt><code>track</code></dt><dd>
The <code>track</code> attribute specifies what the timer
tracks, and can be "boot", "guest", or "wall".
Only valid for <code>name="rtc"</code>
or <code>name="platform"</code>.
</dd><dt><code>tickpolicy</code></dt><dd>
<p>
The <code>tickpolicy</code> attribute determines what
happens whens QEMU misses a deadline for injecting a
tick to the guest:
</p>
<dl><dt><code>delay</code></dt><dd>Continue to deliver ticks at the normal rate.
The guest time will be delayed due to the late
tick</dd><dt><code>catchup</code></dt><dd>Deliver ticks at a higher rate to catch up
with the missed tick. The guest time should
not be delayed once catchup is complete.</dd><dt><code>merge</code></dt><dd>Merge the missed tick(s) into one tick and
inject. The guest time may be delayed, depending
on how the OS reacts to the merging of ticks</dd><dt><code>discard</code></dt><dd>Throw away the missed tick(s) and continue
with future injection normally. The guest time
may be delayed, unless the OS has explicit
handling of lost ticks</dd></dl><p>If the policy is "catchup", there can be further details in
the <code>catchup</code> sub-element.</p>
<dl><dt><code>catchup</code></dt><dd>
The <code>catchup</code> element has three optional
attributes, each a positive integer. The attributes
are <code>threshold</code>, <code>slew</code>,
and <code>limit</code>.
</dd></dl><p>
Note that hypervisors are not required to support all policies across all time sources
</p>
</dd><dt><code>frequency</code></dt><dd>
The <code>frequency</code> attribute is an unsigned
integer specifying the frequency at
which <code>name="tsc"</code> runs.
</dd><dt><code>mode</code></dt><dd>
The <code>mode</code> attribute controls how
the <code>name="tsc"</code> timer is managed, and can be
"auto", "native", "emulate", "paravirt", or "smpsafe".
Other timers are always emulated.
</dd><dt><code>present</code></dt><dd>
The <code>present</code> attribute can be "yes" or "no" to
specify whether a particular timer is available to the guest.
</dd></dl></dd></dl>
<h3>
<a name="elementsDevices" id="elementsDevices">Devices</a>
</h3>
<p>
The final set of XML elements are all used to describe devices
provided to the guest domain. All devices occur as children
of the main <code>devices</code> element.
<span class="since">Since 0.1.3</span>
</p>
<pre>
...
<devices>
<emulator>/usr/lib/xen/bin/qemu-dm</emulator>
</devices>
...</pre>
<dl><dt><code>emulator</code></dt><dd>
The contents of the <code>emulator</code> element specify
the fully qualified path to the device model emulator binary.
The <a href="formatcaps.html">capabilities XML</a> specifies
the recommended default emulator to use for each particular
domain type / architecture combination.
</dd></dl>
<h4>
<a name="elementsDisks" id="elementsDisks">Hard drives, floppy disks, CDROMs</a>
</h4>
<p>
Any device that looks like a disk, be it a floppy, harddisk,
cdrom, or paravirtualized driver is specified via the <code>disk</code>
element.
</p>
<pre>
...
<devices>
<disk type='file' snapshot='external'>
<driver name="tap" type="aio" cache="default"/>
<source file='/var/lib/xen/images/fv0' startupPolicy='optional'>
<seclabel relabel='no'/>
</source>
<target dev='hda' bus='ide'/>
<iotune>
<total_bytes_sec>10000000</total_bytes_sec>
<read_iops_sec>400000</read_iops_sec>
<write_iops_sec>100000</write_iops_sec>
</iotune>
<boot order='2'/>
<encryption type='...'>
...
</encryption>
<shareable/>
<serial>
...
</serial>
</disk>
...
<disk type='network'>
<driver name="qemu" type="raw" io="threads" ioeventfd="on" event_idx="off"/>
<source protocol="sheepdog" name="image_name">
<host name="hostname" port="7000"/>
</source>
<target dev="hdb" bus="ide"/>
<boot order='1'/>
<transient/>
<address type='drive' controller='0' bus='1' unit='0'/>
</disk>
<disk type='network'>
<driver name="qemu" type="raw"/>
<source protocol="rbd" name="image_name2">
<host name="hostname" port="7000"/>
</source>
<target dev="hdd" bus="ide"/>
<auth username='myuser'>
<secret type='ceph' usage='mypassid'/>
</auth>
</disk>
<disk type='block' device='cdrom'>
<driver name='qemu' type='raw'/>
<target dev='hdc' bus='ide' tray='open'/>
<readonly/>
</disk>
<disk type='block' device='lun'>
<driver name='qemu' type='raw'/>
<source dev='/dev/sda'/>
<target dev='sda' bus='scsi'/>
<address type='drive' controller='0' bus='0' target='3' unit='0'/>
</disk>
</devices>
...</pre>
<dl><dt><code>disk</code></dt><dd>The <code>disk</code> element is the main container for describing
disks. The <code>type</code> attribute is either "file",
"block", "dir", or "network"
and refers to the underlying source for the disk. The optional
<code>device</code> attribute indicates how the disk is to be exposed
to the guest OS. Possible values for this attribute are
"floppy", "disk", "cdrom", and "lun", defaulting to
"disk". "lun" (<span class="since">since 0.9.10</span>) is only
valid when type is "block" and the target element's "bus"
attribute is "virtio", and behaves identically to "disk",
except that generic SCSI commands from the guest are accepted
and passed through to the physical device
- also note that device='lun' will only be recognized for
actual raw devices, never for individual partitions or LVM
partitions (in those cases, the kernel will reject the generic
SCSI commands, making it identical to device='disk').
The optional <code>rawio</code> attribute
(<span class="since">since 0.9.10</span>) indicates whether
the disk is needs rawio capability; valid settings are "yes"
or "no" (default is "no"). If any one disk in a domain has
rawio='yes', rawio capability will be enabled for all disks in
the domain (because, in the case of QEMU, this capability can
only be set on a per-process basis). This attribute is only
valid when device is "lun".
The optional <code>snapshot</code> attribute indicates the default
behavior of the disk during disk snapshots: "internal"
requires a file format such as qcow2 that can store both the
snapshot and the data changes since the snapshot;
"external" will separate the snapshot from the live data; and
"no" means the disk will not participate in snapshots.
Read-only disks default to "no", while the default for other
disks depends on the hypervisor's capabilities. Some
hypervisors allow a per-snapshot choice as well,
during <a href="formatsnapshot.html">domain snapshot
creation</a>. Not all snapshot modes are supported;
for example, <code>snapshot='yes'</code> with a transient disk
generally does not make sense. <span class="since">Since 0.0.3;
"device" attribute since 0.1.4;
"network" attribute since 0.8.7; "snapshot" since
0.9.5</span></dd><dt><code>source</code></dt><dd>If the disk <code>type</code> is "file", then
the <code>file</code> attribute specifies the fully-qualified
path to the file holding the disk. If the disk
<code>type</code> is "block", then the <code>dev</code>
attribute specifies the path to the host device to serve as
the disk. With both "file" and "block", an optional
sub-element <code>seclabel</code>, <a href="#seclabel">described
below</a> (and <span class="since">since 0.9.9</span>), can be
used to override the domain security labeling policy for just
that source file. If the disk <code>type</code> is "dir", then the
<code>dir</code> attribute specifies the fully-qualified path
to the directory to use as the disk. If the disk <code>type</code>
is "network", then the <code>protocol</code> attribute specifies
the protocol to access to the requested image; possible values
are "nbd", "rbd", and "sheepdog". If the <code>protocol</code>
attribute is "rbd" or "sheepdog", an additional
attribute <code>name</code> is mandatory to specify which
image will be used. When the disk <code>type</code> is
"network", the <code>source</code> may have zero or
more <code>host</code> sub-elements used to specify the hosts
to connect.
<span class="since">Since 0.0.3; <code>type='dir'</code> since
0.7.5; <code>type='network'</code> since 0.8.7</span><br />
For a "file" disk type which represents a cdrom or floppy
(the <code>device</code> attribute), it is possible to define
policy what to do with the disk if the source file is not accessible.
This is done by the <code>startupPolicy</code> attribute, accepting
these values:
<table class="top_table"><tr><td> mandatory </td><td> fail if missing for any reason (the default) </td></tr><tr><td> requisite </td><td> fail if missing on boot up,
drop if missing on migrate/restore/revert </td></tr><tr><td> optional </td><td> drop if missing at any start attempt </td></tr></table><span class="since">Since 0.9.7</span>
</dd><dt><code>target</code></dt><dd>The <code>target</code> element controls the bus / device
under which the disk is exposed to the guest
OS. The <code>dev</code> attribute indicates the "logical"
device name. The actual device name specified is not
guaranteed to map to the device name in the guest OS. Treat it
as a device ordering hint. The optional <code>bus</code>
attribute specifies the type of disk device to emulate;
possible values are driver specific, with typical values being
"ide", "scsi", "virtio", "xen", "usb" or "sata". If omitted, the bus
type is inferred from the style of the device name. eg, a device named
'sda' will typically be exported using a SCSI bus. The optional
attribute <code>tray</code> indicates the tray status of the
removable disks (i.e. CDROM or Floppy disk), the value can be either
"open" or "closed", defaults to "closed". NB, the value of
<code>tray</code> could be updated while the domain is running.
<span class="since">Since 0.0.3; <code>bus</code> attribute since 0.4.3;
<code>tray</code> attribute since 0.9.11; "usb" attribute value since
after 0.4.4; "sata" attribute value since 0.9.7</span>
</dd><dt><code>iotune</code></dt><dd>The optional <code>iotune</code> element provides the
ability to provide additional per-device I/O tuning, with
values that can vary for each device (contrast this to
the <a href="#elementsBlockTuning"><code><blkiotune></code></a>
element, which applies globally to the domain). Currently,
the only tuning available is Block I/O throttling for qemu.
This element has optional sub-elements; any sub-element not
specified or given with a value of 0 implies no
limit. <span class="since">Since 0.9.8</span>
<dl><dt><code>total_bytes_sec</code></dt><dd>The optional <code>total_bytes_sec</code> element is the
total throughput limit in bytes per second. This cannot
appear with <code>read_bytes_sec</code>
or <code>write_bytes_sec</code>.</dd><dt><code>read_bytes_sec</code></dt><dd>The optional <code>read_bytes_sec</code> element is the
read throughput limit in bytes per second.</dd><dt><code>write_bytes_sec</code></dt><dd>The optional <code>write_bytes_sec</code> element is the
write throughput limit in bytes per second.</dd><dt><code>total_iops_sec</code></dt><dd>The optional <code>total_iops_sec</code> element is the
total I/O operations per second. This cannot
appear with <code>read_iops_sec</code>
or <code>write_iops_sec</code>.</dd><dt><code>read_iops_sec</code></dt><dd>The optional <code>read_iops_sec</code> element is the
read I/O operations per second.</dd><dt><code>write_iops_sec</code></dt><dd>The optional <code>write_iops_sec</code> element is the
write I/O operations per second.</dd></dl></dd><dt><code>driver</code></dt><dd>
The optional driver element allows specifying further details
related to the hypervisor driver used to provide the disk.
<span class="since">Since 0.1.8</span>
<ul><li>
If the hypervisor supports multiple backend drivers, then
the <code>name</code> attribute selects the primary
backend driver name, while the optional <code>type</code>
attribute provides the sub-type. For example, xen
supports a name of "tap", "tap2", "phy", or "file", with a
type of "aio", while qemu only supports a name of "qemu",
but multiple types including "raw", "bochs", "qcow2", and
"qed".
</li><li>
The optional <code>cache</code> attribute controls the
cache mechanism, possible values are "default", "none",
"writethrough", "writeback", "directsync" (like
"writethrough", but it bypasses the host page cache) and
"unsafe" (host may cache all disk io, and sync requests from
guest are ignored).
<span class="since">
Since 0.6.0,
"directsync" since 0.9.5,
"unsafe" since 0.9.7
</span>
</li><li>
The optional <code>error_policy</code> attribute controls
how the hypervisor will behave on a disk read or write
error, possible values are "stop", "report", "ignore", and
"enospace".<span class="since">Since 0.8.0, "report" since
0.9.7</span> The default setting of error_policy is "report".
There is also an
optional <code>rerror_policy</code> that controls behavior
for read errors only. <span class="since">Since
0.9.7</span>. If no rerror_policy is given, error_policy
is used for both read and write errors. If rerror_policy
is given, it overrides the <code>error_policy</code> for
read errors. Also note that "enospace" is not a valid
policy for read errors, so if <code>error_policy</code> is
set to "enospace" and no <code>rerror_policy</code> is
given, the read error policy will be left at its default,
which is "report".
</li><li>
The optional <code>io</code> attribute controls specific
policies on I/O; qemu guests support "threads" and
"native". <span class="since">Since 0.8.8</span>
</li><li>
The optional <code>ioeventfd</code> attribute allows users to
set <a href="https://patchwork.kernel.org/patch/43390/">
domain I/O asynchronous handling</a> for disk device.
The default is left to the discretion of the hypervisor.
Accepted values are "on" and "off". Enabling this allows
qemu to execute VM while a separate thread handles I/O.
Typically guests experiencing high system CPU utilization
during I/O will benefit from this. On the other hand,
on overloaded host it could increase guest I/O latency.
<span class="since">Since 0.9.3 (QEMU and KVM only)</span>
<b>In general you should leave this option alone, unless you
are very certain you know what you are doing.</b>
</li><li>
The optional <code>event_idx</code> attribute controls
some aspects of device event processing. The value can be
either 'on' or 'off' - if it is on, it will reduce the
number of interupts and exits for the guest. The default
is determined by QEMU; usually if the feature is
supported, default is on. In case there is a situation
where this behavior is suboptimal, this attribute provides
a way to force the feature off.
<span class="since">Since 0.9.5 (QEMU and KVM only)</span>
<b>In general you should leave this option alone, unless you
are very certain you know what you are doing.</b>
</li><li>
The optional <code>copy_on_read</code> attribute controls
wether to copy read backing file into the image file. The
value can be either "on" or "off".
Copy-on-read avoids accessing the same backing file sectors
repeatedly and is useful when the backing file is over a slow
network. By default copy-on-read is off.
<span class="since">Since 0.9.10 (QEMU and KVM only)</span>
</li></ul></dd><dt><code>boot</code></dt><dd>Specifies that the disk is bootable. The <code>order</code>
attribute determines the order in which devices will be tried during
boot sequence. The per-device <code>boot</code> elements cannot be
used together with general boot elements in
<a href="#elementsOSBIOS">BIOS bootloader</a> section.
<span class="since">Since 0.8.8</span>
</dd><dt><code>encryption</code></dt><dd>If present, specifies how the volume is encrypted. See
the <a href="formatstorageencryption.html">Storage Encryption</a> page
for more information.
</dd><dt><code>readonly</code></dt><dd>If present, this indicates the device cannot be modified by
the guest. For now, this is the default for disks with
attribute <code>type='cdrom'</code>.
</dd><dt><code>shareable</code></dt><dd>If present, this indicates the device is expected to be shared
between domains (assuming the hypervisor and OS support this),
which means that caching should be deactivated for that device.
</dd><dt><code>transient</code></dt><dd>If present, this indicates that changes to the device
contents should be reverted automatically when the guest
exits. With some hypervisors, marking a disk transient
prevents the domain from participating in migration or
snapshots. <span class="since">Since 0.9.5</span>
</dd><dt><code>serial</code></dt><dd>If present, this specify serial number of virtual hard drive.
For example, it may look
like <code><serial>WD-WMAP9A966149</serial></code>.
<span class="since">Since 0.7.1</span>
</dd><dt><code>host</code></dt><dd>The <code>host</code> element has two attributes "name" and "port",
which specify the hostname and the port number. The meaning of this
element and the number of the elements depend on the protocol attribute.
<table class="top_table"><tr><th> Protocol </th><th> Meaning </th><th> Number of hosts </th></tr><tr><td> nbd </td><td> a server running nbd-server </td><td> only one </td></tr><tr><td> rbd </td><td> monitor servers of RBD </td><td> one or more </td></tr><tr><td> sheepdog </td><td> one of the sheepdog servers (default is localhost:7000) </td><td> zero or one </td></tr></table></dd><dt><code>address</code></dt><dd>If present, the <code>address</code> element ties the disk
to a given slot of a controller (the
actual <code><controller></code> device can often be
inferred by libvirt, although it can
be <a href="#elementsControllers">explicitly specified</a>).
The <code>type</code> attribute is mandatory, and is typically
"pci" or "drive". For a "pci" controller, additional
attributes for <code>bus</code>, <code>slot</code>,
and <code>function</code> must be present, as well as
optional <code>domain</code> and <code>multifunction</code>.
Multifunction defaults to 'off'; any other value requires
QEMU 0.1.3 and <span class="since">libvirt 0.9.7</span>. For a
"drive" controller, additional attributes
<code>controller</code>, <code>bus</code>, <code>target</code>
(<span class="since">libvirt 0.9.11</span>), and <code>unit</code>
are available, each defaulting to 0.
</dd><dt><code>auth</code></dt><dd>If present, the <code>auth</code> element provides the
authentication credentials needed to access the source. It
includes a mandatory attribute <code>username</code>, which
identifies the username to use during authentication, as well
as a sub-element <code>secret</code> with mandatory
attribute <code>type</code>, to tie back to
a <a href="formatsecret.html">libvirt secret object</a> that
holds the actual password or other credentials (the domain XML
intentionally does not expose the password, only the reference
to the object that does manage the password). For now, the
only known secret <code>type</code> is "ceph", for Ceph RBD
network sources, and requires either an
attribute <code>uuid</code> with the UUID of the Ceph secret
object, or an attribute <code>usage</code> with the name
associated with the Ceph secret
object. <span class="since">libvirt 0.9.7</span>
</dd></dl>
<h4>
<a name="elementsFilesystems" id="elementsFilesystems">Filesystems</a>
</h4>
<p>
A directory on the host that can be accessed directly from the guest.
<span class="since">since 0.3.3, since 0.8.5 for QEMU/KVM</span>
</p>
<pre>
...
<devices>
<filesystem type='template'>
<source name='my-vm-template'/>
<target dir='/'/>
</filesystem>
<filesystem type='mount' accessmode='passthrough'>
<driver type='path' wrpolicy='immediate'/>
<source dir='/export/to/guest'/>
<target dir='/import/from/host'/>
<readonly/>
</filesystem>
...
</devices>
...</pre>
<dl><dt><code>filesystem</code></dt><dd>
The filesystem attribute <code>type</code> specifies the type of the
<code>source</code>. The possible values are:
<dl><dt><code>type='mount'</code></dt><dd>
A host directory to mount in the guest. Used by LXC,
OpenVZ <span class="since">(since 0.6.2)</span>
and QEMU/KVM <span class="since">(since 0.8.5)</span>.
This is the default <code>type</code> if one is not specified.
This mode also has an optional
sub-element <code>driver</code>, with an
attribute <code>type='path'</code>
or <code>type='handle'</code> <span class="since">(since
0.9.7)</span>. The driver block has an optional attribute
<code>wrpolicy</code> that further controls interaction with
the host page cache; omitting the attribute gives default behavior,
while the value <code>immediate</code> means that a host writeback
is immediately triggered for all pages touched during a guest file
write operation <span class="since">(since 0.9.10)</span>.
</dd><dt><code>type='template'</code></dt><dd>
OpenVZ filesystem template. Only used by OpenVZ driver.
</dd><dt><code>type='file'</code></dt><dd>
Currently unused.
</dd><dt><code>type='block'</code></dt><dd>
A host block device to mount in the guest. The filesystem
format will be autodetected. Only used by LXC driver
<span class="since">(since 0.9.5)</span>.
</dd></dl>
The filesystem block has an optional attribute <code>accessmode</code>
which specifies the security mode for accessing the source
<span class="since">(since 0.8.5)</span>. Currently this only works
with <code>type='mount'</code> for the QEMU/KVM driver. The possible
values are:
<dl><dt><code>accessmode='passthrough'</code></dt><dd>
The <code>source</code> is accessed with the permissions of the
user inside the guest. This is the default <code>accessmode</code> if
one is not specified.
<a href="http://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02673.html">More info</a>
</dd><dt><code>accessmode='mapped'</code></dt><dd>
The <code>source</code> is accessed with the permissions of the
hypervisor (QEMU process).
<a href="http://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02673.html">More info</a>
</dd><dt><code>accessmode='squash'</code></dt><dd>
Similar to 'passthrough', the exception is that failure of
privileged operations like 'chown' are ignored. This makes a
passthrough-like mode usable for people who run the hypervisor
as non-root.
<a href="http://lists.gnu.org/archive/html/qemu-devel/2010-09/msg00121.html">More info</a>
</dd></dl></dd><dt><code>source</code></dt><dd>
The resource on the host that is being accessed in the guest. The
<code>name</code> attribute must be used with
<code>type='template'</code>, and the <code>dir</code> attribute must
be used with <code>type='mount'</code>
</dd><dt><code>target</code></dt><dd>
Where the <code>source</code> can be accessed in the guest. For
most drivers this is an automatic mount point, but for QEMU/KVM
this is merely an arbitrary string tag that is exported to the
guest as a hint for where to mount.
</dd><dt><code>readonly</code></dt><dd>
Enables exporting filesytem as a readonly mount for guest, by
default read-write access is given (currently only works for
QEMU/KVM driver).
</dd></dl>
<h4>
<a name="elementsAddress" id="elementsAddress">Device Addresses</a>
</h4>
<p>
Many devices have an optional <code><address></code>
sub-element to describe where the device is placed on the
virtual bus presented to the guest. If an address (or any
optional attribute within an address) is omitted on
input, libvirt will generate an appropriate address; but an
explicit address is required if more control over layout is
required. See below for device examples including an address
element.
</p>
<p>
Every address has a mandatory attribute <code>type</code> that
describes which bus the device is on. The choice of which
address to use for a given device is constrained in part by the
device and the architecture of the guest. For example,
a <code><disk></code> device
uses <code>type='disk'</code>, while
a <code><console></code> device would
use <code>type='pci'</code> on i686 or x86_64 guests,
or <code>type='spapr-vio'</code> on PowerPC64 pseries guests.
Each address type has further optional attributes that control
where on the bus the device will be placed:
</p>
<dl><dt><code>type='pci'</code></dt><dd>PCI addresses have the following additional
attributes: <code>domain</code> (a 2-byte hex integer, not
currently used by qemu), <code>bus</code> (a hex value between
0 and 0xff, inclusive), <code>slot</code> (a hex value between
0x0 and 0x1f, inclusive), and <code>function</code> (a value
between 0 and 7, inclusive). Also available is
the <code>multifunction</code> attribute, which controls
turning on the multifunction bit for a particular
slot/function in the PCI control register
(<span class="since">since 0.9.7, requires QEMU
0.13</span>). <code>multifunction</code> defaults to 'off',
but should be set to 'on' for function 0 of a slot that will
have multiple functions used.
</dd><dt><code>type='drive'</code></dt><dd>Drive addresses have the following additional
attributes: <code>controller</code> (a 2-digit controller
number), <code>bus</code> (a 2-digit bus number),
<code>target</code> (a 2-digit bus number),
and <code>unit</code> (a 2-digit unit number on the bus).
</dd><dt><code>type='virtio-serial'</code></dt><dd>Each virtio-serial address has the following additional
attributes: <code>controller</code> (a 2-digit controller
number), <code>bus</code> (a 2-digit bus number),
and <code>slot</code> (a 2-digit slot within the bus).
</dd><dt><code>type='ccid'</code></dt><dd>A CCID address, for smart-cards, has the following
additional attributes: <code>bus</code> (a 2-digit bus
number), and <code>slot</code> attribute (a 2-digit slot
within the bus). <span class="since">Since 0.8.8.</span>
</dd><dt><code>type='usb'</code></dt><dd>USB addresses have the following additional
attributes: <code>bus</code> (a hex value between 0 and 0xfff,
inclusive), and <code>port</code> (a dotted notation of up to
four octets, such as 1.2 or 2.1.3.1).
</dd><dt><code>type='spapr-vio'</code></dt><dd>On PowerPC pseries guests, devices can be assigned to the
SPAPR-VIO bus. It has a flat 64-bit address space; by
convention, devices are generally assigned at a non-zero
multiple of 0x1000, but other addresses are valid and
permitted by libvirt. Each address has the following
additional attribute: <code>reg</code> (the hex value address
of the starting register). <span class="since">Since
0.9.9.</span>
</dd></dl>
<h4>
<a name="elementsControllers" id="elementsControllers">Controllers</a>
</h4>
<p>
Depending on the guest architecture, some device busses can
appear more than once, with a group of virtual devices tied to a
virtual controller. Normally, libvirt can automatically infer such
controllers without requiring explicit XML markup, but sometimes
it is necessary to provide an explicit controller element.
</p>
<pre>
...
<devices>
<controller type='ide' index='0'/>
<controller type='virtio-serial' index='0' ports='16' vectors='4'/>
<controller type='virtio-serial' index='1'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>
</controller>
...
</devices>
...</pre>
<p>
Each controller has a mandatory attribute <code>type</code>,
which must be one of "ide", "fdc", "scsi", "sata", "usb",
"ccid", or "virtio-serial", and a mandatory
attribute <code>index</code> which is the decimal integer
describing in which order the bus controller is encountered (for
use in <code>controller</code> attributes
of <code><address></code> elements). The "virtio-serial"
controller has two additional optional
attributes <code>ports</code> and <code>vectors</code>, which
control how many devices can be connected through the
controller. A "scsi" controller has an optional
attribute <code>model</code>, which is one of "auto", "buslogic",
"ibmvscsi", "lsilogic", "lsias1068", "virtio-scsi" or "vmpvscsi".
A "usb" controller has an optional attribute <code>model</code>,
which is one of "piix3-uhci", "piix4-uhci", "ehci",
"ich9-ehci1", "ich9-uhci1", "ich9-uhci2", "ich9-uhci3",
"vt82c686b-uhci" or "pci-ohci". The PowerPC64 "spapr-vio"
addresses do not have an associated controller.
</p>
<p>
For controllers that are themselves devices on a PCI or USB bus,
an optional sub-element <code><address></code> can specify
the exact relationship of the controller to its master bus, with
semantics <a href="#elementsAddress">given above</a>.
</p>
<p>
USB companion controllers have an optional
sub-element <code><master></code> to specify the exact
relationship of the companion to its master controller.
A companion controller is on the same bus as its master, so
the companion <code>index</code> value should be equal.
</p>
<pre>
...
<devices>
<controller type='usb' index='0' model='ich9-ehci1'>
<address type='pci' domain='0' bus='0' slot='4' function='7'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci1'>
<master startport='0'/>
<address type='pci' domain='0' bus='0' slot='4' function='0' multifunction='on'/>
</controller>
...
</devices>
...</pre>
<h4>
<a name="elementsLease" id="elementsLease">Device leases</a>
</h4>
<p>
When using a lock manager, it may be desirable to record device leases
against a VM. The lock manager will ensure the VM won't start unless
the leases can be acquired.
</p>
<pre>
...
<devices>
...
<lease>
<lockspace>somearea</lockspace>
<key>somekey</key>
<target path='/some/lease/path' offset='1024'/>
</lease>
...
</devices>
...</pre>
<dl><dt>lockspace</dt><dd>This is an arbitrary string, identifying the lockspace
within which the key is held. Lock managers may impose
extra restrictions on the format, or length of the lockspace
name.</dd><dt>key</dt><dd>This is an arbitrary string, uniquely identifying the
lease to be acquired. Lock managers may impose extra
restrictions on the format, or length of the key.
</dd><dt>target</dt><dd>This is the fully qualified path of the file associated
with the lockspace. The offset specifies where the lease
is stored within the file. If the lock manager does not
require a offset, just pass 0.
</dd></dl>
<h4>
<a name="elementsUSB" id="elementsUSB">USB and PCI devices</a>
</h4>
<p>
USB and PCI devices attached to the host can be passed through
to the guest using
the <code>hostdev</code> element. <span class="since">since after
0.4.4 for USB and 0.6.0 for PCI (KVM only)</span>:
</p>
<pre>
...
<devices>
<hostdev mode='subsystem' type='usb'>
<source>
<vendor id='0x1234'/>
<product id='0xbeef'/>
</source>
<boot order='2'/>
</hostdev>
</devices>
...</pre>
<p>or:</p>
<pre>
...
<devices>
<hostdev mode='subsystem' type='pci' managed='yes'>
<source>
<address bus='0x06' slot='0x02' function='0x0'/>
</source>
<boot order='1'/>
<rom bar='on' file='/etc/fake/boot.bin'/>
</hostdev>
</devices>
...</pre>
<dl><dt><code>hostdev</code></dt><dd>The <code>hostdev</code> element is the main container for describing
host devices. For usb device passthrough <code>mode</code> is always
"subsystem" and <code>type</code> is "usb" for a USB device and "pci"
for a PCI device. When <code>managed</code> is "yes" for a PCI
device, it is detached from the host before being passed on to
the guest, and reattached to the host after the guest exits.
If <code>managed</code> is omitted or "no", and for USB
devices, the user is responsible to
call <code>virNodeDeviceDettach</code> (or <code>virsh
nodedev-dettach</code>) before starting the guest or
hot-plugging the device,
and <code>virNodeDeviceReAttach</code> (or <code>virsh
nodedev-reattach</code>) after hot-unplug or stopping the
guest.</dd><dt><code>source</code></dt><dd>The source element describes the device as seen from the host.
The USB device can either be addressed by vendor / product id using the
<code>vendor</code> and <code>product</code> elements or by the device's
address on the hosts using the <code>address</code> element.
PCI devices on the other hand can only be described by their
<code>address</code></dd><dt><code>vendor</code>, <code>product</code></dt><dd>The <code>vendor</code> and <code>product</code> elements each have an
<code>id</code> attribute that specifies the USB vendor and product id.
The ids can be given in decimal, hexadecimal (starting with 0x) or
octal (starting with 0) form.</dd><dt><code>boot</code></dt><dd>Specifies that the device is bootable. The <code>order</code>
attribute determines the order in which devices will be tried during
boot sequence. The per-device <code>boot</code> elements cannot be
used together with general boot elements in
<a href="#elementsOSBIOS">BIOS bootloader</a> section.
<span class="since">Since 0.8.8</span></dd><dt><code>rom</code></dt><dd>The <code>rom</code> element is used to change how a PCI
device's ROM is presented to the guest. The optional <code>bar</code>
attribute can be set to "on" or "off", and determines whether
or not the device's ROM will be visible in the guest's memory
map. (In PCI documentation, the "rombar" setting controls the
presence of the Base Address Register for the ROM). If no rom
bar is specified, the qemu default will be used (older
versions of qemu used a default of "off", while newer qemus
have a default of "on"). <span class="since">Since
0.9.7 (QEMU and KVM only)</span>. The optional
<code>file</code> attribute is used to point to a binary file
to be presented to the guest as the device's ROM BIOS. This
can be useful, for example, to provide a PXE boot ROM for a
virtual function of an sr-iov capable ethernet device (which
has no boot ROMs for the VFs).
<span class="since">Since 0.9.10 (QEMU and KVM only)</span>.
</dd><dt><code>address</code></dt><dd>The <code>address</code> element for USB devices has a
<code>bus</code> and <code>device</code> attribute to specify the
USB bus and device number the device appears at on the host.
The values of these attributes can be given in decimal, hexadecimal
(starting with 0x) or octal (starting with 0) form.
For PCI devices the element carries 3 attributes allowing to designate
the device as can be found with the <code>lspci</code> or
with <code>virsh
nodedev-list</code>. <a href="#elementsAddress">See above</a> for
more details on the address element.
</dd></dl>
<h4>
<a name="elementsRedir" id="elementsRedir">Redirected devices</a>
</h4>
<p>
USB device redirection through a character device is
supported <span class="since">since after 0.9.5 (KVM
only)</span>:
</p>
<pre>
...
<devices>
<redirdev bus='usb' type='tcp'>
<source mode='connect' host='localhost' service='4000'/>
</redirdev>
</devices>
...</pre>
<dl><dt><code>redirdev</code></dt><dd>The <code>redirdev</code> element is the main container for
describing redirected devices. <code>bus</code> must be "usb"
for a USB device.
An additional attribute <code>type</code> is required,
matching one of the
supported <a href="#elementsConsole">serial device</a> types,
to describe the host side of the
tunnel; <code>type='tcp'</code>
or <code>type='spicevmc'</code> (which uses the usbredir
channel of a <a href="#elementsGraphics">SPICE graphics
device</a>) are typical.</dd></dl>
<p>
The redirdev element has an optional sub-element
<code><address></code> which can tie the device to a
particular controller.
</p>
<p>
Further sub-elements, such as <code><source></code>, may
be required according to the given type, although
a <code><target></code> sub-element is not required (since
the consumer of the character device is the hypervisor itself,
rather than a device visible in the guest).
</p>
<h4>
<a name="elementsSmartcard" id="elementsSmartcard">Smartcard devices</a>
</h4>
<p>
A virtual smartcard device can be supplied to the guest via the
<code>smartcard</code> element. A USB smartcard reader device on
the host cannot be used on a guest with simple device
passthrough, since it will then not be available on the host,
possibly locking the host computer when it is "removed".
Therefore, some hypervisors provide a specialized virtual device
that can present a smartcard interface to the guest, with
several modes for describing how credentials are obtained from
the host or even a from a channel created to a third-party
smartcard provider. <span class="since">Since 0.8.8</span>
</p>
<pre>
...
<devices>
<smartcard mode='host'/>
<smartcard mode='host-certificates'>
<certificate>cert1</certificate>
<certificate>cert2</certificate>
<certificate>cert3</certificate>
<database>/etc/pki/nssdb/</database>
</smartcard>
<smartcard mode='passthrough' type='tcp'>
<source mode='bind' host='127.0.0.1' service='2001'/>
<protocol type='raw'/>
<address type='ccid' controller='0' slot='0'/>
</smartcard>
<smartcard mode='passthrough' type='spicevmc'/>
</devices>
...
</pre>
<p>
The <code><smartcard></code> element has a mandatory
attribute <code>mode</code>. The following modes are supported;
in each mode, the guest sees a device on its USB bus that
behaves like a physical USB CCID (Chip/Smart Card Interface
Device) card.
</p>
<dl><dt><code>mode='host'</code></dt><dd>The simplest operation, where the hypervisor relays all
requests from the guest into direct access to the host's
smartcard via NSS. No other attributes or sub-elements are
required. See below about the use of an
optional <code><address></code> sub-element.</dd><dt><code>mode='host-certificates'</code></dt><dd>Rather than requiring a smartcard to be plugged into the
host, it is possible to provide three NSS certificate names
residing in a database on the host. These certificates can be
generated via the command <code>certutil -d /etc/pki/nssdb -x -t
CT,CT,CT -S -s CN=cert1 -n cert1</code>, and the resulting three
certificate names must be supplied as the content of each of
three <code><certificate></code> sub-elements. An
additional sub-element <code><database></code> can specify
the absolute path to an alternate directory (matching
the <code>-d</code> option of the <code>certutil</code> command
when creating the certificates); if not present, it defaults to
/etc/pki/nssdb.</dd><dt><code>mode='passthrough'</code></dt><dd>Rather than having the hypervisor directly communicate with
the host, it is possible to tunnel all requests through a
secondary character device to a third-party provider (which may
in turn be talking to a smartcard or using three certificate
files). In this mode of operation, an additional
attribute <code>type</code> is required, matching one of the
supported <a href="#elementsConsole">serial device</a> types, to
describe the host side of the tunnel; <code>type='tcp'</code>
or <code>type='spicevmc'</code> (which uses the smartcard
channel of a <a href="#elementsGraphics">SPICE graphics
device</a>) are typical. Further sub-elements, such
as <code><source></code>, may be required according to the
given type, although a <code><target></code> sub-element
is not required (since the consumer of the character device is
the hypervisor itself, rather than a device visible in the
guest).</dd></dl>
<p>
Each mode supports an optional
sub-element <code><address></code>, which fine-tunes the
correlation between the smartcard and a ccid bus
controller, <a href="#elementsAddress">documented above</a>.
For now, qemu only supports at most one
smartcard, with an address of bus=0 slot=0.
</p>
<h4>
<a name="elementsNICS" id="elementsNICS">Network interfaces</a>
</h4>
<pre>
...
<devices>
<interface type='bridge'>
<source bridge='xenbr0'/>
<mac address='00:16:3e:5d:c7:9e'/>
<script path='vif-bridge'/>
<boot order='1'/>
<rom bar='off'/>
</interface>
</devices>
...</pre>
<p>
There are several possibilities for specifying a network
interface visible to the guest. Each subsection below provides
more details about common setup options. Additionally,
each <code><interface></code> element has an
optional <code><address></code> sub-element that can tie
the interface to a particular pci slot, with
attribute <code>type='pci'</code>
as <a href="#elementsAddress">documented above</a>.
</p>
<h5>
<a name="elementsNICSVirtual" id="elementsNICSVirtual">Virtual network</a>
</h5>
<p>
<strong><em>
This is the recommended config for general guest connectivity on
hosts with dynamic / wireless networking configs (or multi-host
environments where the host hardware details are described
separately in a <code><network></code>
definition <span class="since">Since 0.9.4</span>).
</em></strong>
</p>
<p>
Provides a connection whose details are described by the named
network definition. Depending on the virtual network's "forward
mode" configuration, the network may be totally isolated
(no <code><forward></code> element given), NAT'ing to an
explicit network device or to the default route
(<code><forward mode='nat'></code>), routed with no NAT
(<code><forward mode='route'/></code>), or connected
directly to one of the host's network interfaces (via macvtap)
or bridge devices ((<code><forward
mode='bridge|private|vepa|passthrough'/></code> <span class="since">Since
0.9.4</span>)
</p>
<p>
For networks with a forward mode of bridge, private, vepa, and
passthrough, it is assumed that the host has any necessary DNS
and DHCP services already setup outside the scope of libvirt. In
the case of isolated, nat, and routed networks, DHCP and DNS are
provided on the virtual network by libvirt, and the IP range can
be determined by examining the virtual network config with
'<code>virsh net-dumpxml [networkname]</code>'. There is one
virtual network called 'default' setup out of the box which does
NAT'ing to the default route and has an IP range
of <code>192.168.122.0/255.255.255.0</code>. Each guest will
have an associated tun device created with a name of vnetN,
which can also be overridden with the <target> element
(see
<a href="#elementsNICSTargetOverride">overriding the target element</a>).
</p>
<p>
When the source of an interface is a network,
a <code>portgroup</code> can be specified along with the name of
the network; one network may have multiple portgroups defined,
with each portgroup containing slightly different configuration
information for different classes of network
connections. <span class="since">Since 0.9.4</span>). Also,
similar to <code>direct</code> network connections (described
below), a connection of type <code>network</code> may specify
a <code>virtportprofile</code> element, with configuration data
to be forwarded to a vepa or 802.1Qbh compliant switch.
</p>
<pre>
...
<devices>
<interface type='network'>
<source network='default'/>
</interface>
...
<interface type='network'>
<source network='default' portgroup='engineering'/>
<target dev='vnet7'/>
<mac address="00:11:22:33:44:55"/>
<virtualport type='802.1Qbg'>
<parameters managerid='11' typeid='1193047' typeidversion='2' instanceid='09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f'/>
</virtualport>
</interface>
</devices>
...</pre>
<h5>
<a name="elementsNICSBridge" id="elementsNICSBridge">Bridge to LAN</a>
</h5>
<p>
<strong><em>
This is the recommended config for general guest connectivity on
hosts with static wired networking configs
</em></strong>
</p>
<p>
Provides a bridge from the VM directly onto the LAN. This assumes
there is a bridge device on the host which has one or more of the hosts
physical NICs enslaved. The guest VM will have an associated tun device
created with a name of vnetN, which can also be overridden with the
<target> element (see
<a href="#elementsNICSTargetOverride">overriding the target element</a>).
The tun device will be enslaved to the bridge. The IP range / network
configuration is whatever is used on the LAN. This provides the guest VM
full incoming & outgoing net access just like a physical machine.
</p>
<pre>
...
<devices>
<interface type='bridge'>
<source bridge='br0'/>
</interface>
...
<interface type='bridge'>
<source bridge='br0'/>
<target dev='vnet7'/>
<mac address="00:11:22:33:44:55"/>
</interface>
</devices>
...</pre>
<h5>
<a name="elementsNICSSlirp" id="elementsNICSSlirp">Userspace SLIRP stack</a>
</h5>
<p>
Provides a virtual LAN with NAT to the outside world. The virtual
network has DHCP & DNS services and will give the guest VM addresses
starting from <code>10.0.2.15</code>. The default router will be
<code>10.0.2.2</code> and the DNS server will be <code>10.0.2.3</code>.
This networking is the only option for unprivileged users who need their
VMs to have outgoing access.
</p>
<pre>
...
<devices>
<interface type='user'/>
...
<interface type='user'>
<mac address="00:11:22:33:44:55"/>
</interface>
</devices>
...</pre>
<h5>
<a name="elementsNICSEthernet" id="elementsNICSEthernet">Generic ethernet connection</a>
</h5>
<p>
Provides a means for the administrator to execute an arbitrary script
to connect the guest's network to the LAN. The guest will have a tun
device created with a name of vnetN, which can also be overridden with the
<target> element. After creating the tun device a shell script will
be run which is expected to do whatever host network integration is
required. By default this script is called /etc/qemu-ifup but can be
overridden.
</p>
<pre>
...
<devices>
<interface type='ethernet'/>
...
<interface type='ethernet'>
<target dev='vnet7'/>
<script path='/etc/qemu-ifup-mynet'/>
</interface>
</devices>
...</pre>
<h5>
<a name="elementsNICSDirect" id="elementsNICSDirect">Direct attachment to physical interface</a>
</h5>
<p>
Provides direct attachment of the virtual machine's NIC to the given
physial interface of the host.
<span class="since">Since 0.7.7 (QEMU and KVM only)</span><br />
This setup requires the Linux macvtap
driver to be available. <span class="since">(Since Linux 2.6.34.)</span>
One of the modes 'vepa'
( <a href="http://www.ieee802.org/1/files/public/docs2009/new-evb-congdon-vepa-modular-0709-v01.pdf">
'Virtual Ethernet Port Aggregator'</a>), 'bridge' or 'private'
can be chosen for the operation mode of the macvtap device, 'vepa'
being the default mode. The individual modes cause the delivery of
packets to behave as follows:
</p>
<dl><dt><code>vepa</code></dt><dd>All VMs' packets are sent to the external bridge. Packets
whose destination is a VM on the same host as where the
packet originates from are sent back to the host by the VEPA
capable bridge (today's bridges are typically not VEPA capable).</dd><dt><code>bridge</code></dt><dd>Packets whose destination is on the same host as where they
originate from are directly delivered to the target macvtap device.
Both origin and destination devices need to be in bridge mode
for direct delivery. If either one of them is in <code>vepa</code> mode,
a VEPA capable bridge is required.</dd><dt><code>private</code></dt><dd>All packets are sent to the external bridge and will only be
delivered to a target VM on the same host if they are sent through an
external router or gateway and that device sends them back to the
host. This procedure is followed if either the source or destination
device is in <code>private</code> mode.</dd><dt><code>passthrough</code></dt><dd>This feature attaches a virtual function of a SRIOV capable
NIC directly to a VM without losing the migration capability.
All packets are sent to the VF/IF of the configured network device.
Depending on the capabilities of the device additional prerequisites or
limitations may apply; for example, on Linux this requires
kernel 2.6.38 or newer. <span class="since">Since 0.9.2</span></dd></dl>
<pre>
...
<devices>
...
<interface type='direct'>
<source dev='eth0' mode='vepa'/>
</interface>
</devices>
...</pre>
<p>
The network access of direct attached virtual machines can be
managed by the hardware switch to which the physical interface
of the host machine is connected to.
</p>
<p>
The interface can have additional parameters as shown below,
if the switch is conforming to the IEEE 802.1Qbg standard.
The parameters of the virtualport element are documented in more detail
in the IEEE 802.1Qbg standard. The values are network specific and
should be provided by the network administrator. In 802.1Qbg terms,
the Virtual Station Interface (VSI) represents the virtual interface
of a virtual machine. <span class="since">Since 0.8.2</span>
</p>
<p>
Please note that IEEE 802.1Qbg requires a non-zero value for the
VLAN ID.
</p>
<dl><dt><code>managerid</code></dt><dd>The VSI Manager ID identifies the database containing the VSI type
and instance definitions. This is an integer value and the
value 0 is reserved.</dd><dt><code>typeid</code></dt><dd>The VSI Type ID identifies a VSI type characterizing the network
access. VSI types are typically managed by network administrator.
This is an integer value.
</dd><dt><code>typeidversion</code></dt><dd>The VSI Type Version allows multiple versions of a VSI Type.
This is an integer value.
</dd><dt><code>instanceid</code></dt><dd>The VSI Instance ID Identifier is generated when a VSI instance
(i.e. a virtual interface of a virtual machine) is created.
This is a globally unique identifier.
</dd></dl>
<pre>
...
<devices>
...
<interface type='direct'>
<source dev='eth0.2' mode='vepa'/>
<virtualport type="802.1Qbg">
<parameters managerid="11" typeid="1193047" typeidversion="2" instanceid="09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f"/>
</virtualport>
</interface>
</devices>
...</pre>
<p>
The interface can have additional parameters as shown below
if the switch is conforming to the IEEE 802.1Qbh standard.
The values are network specific and should be provided by the
network administrator. <span class="since">Since 0.8.2</span>
</p>
<dl><dt><code>profileid</code></dt><dd>The profile ID contains the name of the port profile that is to
be applied onto this interface. This name is resolved by the port
profile database into the network parameters from the port profile,
and those network parameters will be applied to this interface.
</dd></dl>
<pre>
...
<devices>
...
<interface type='direct'>
<source dev='eth0' mode='private'/>
<virtualport type='802.1Qbh'>
<parameters profileid='finance'/>
</virtualport>
</interface>
</devices>
...
</pre>
<h5>
<a name="elementsNICSHostdev" id="elementsNICSHostdev">PCI Passthrough</a>
</h5>
<p>
A PCI network device (specified by the <source> element)
is directly assigned to the guest using generic device
passthrough, after first optionally setting the device's MAC
address to the configured value, and associating the device with
an 802.1Qbh capable switch using an optionally specified
<virtualport> element (see the examples of virtualport
given above for type='direct' network devices). Note that - due
to limitations in standard single-port PCI ethernet card driver
design - only SR-IOV (Single Root I/O Virtualization) virtual
function (VF) devices can be assigned in this manner; to assign
a standard single-port PCI or PCIe ethernet card to a guest, use
the traditional <hostdev> device definition and
<span class="since">Since 0.9.11</span>
</p>
<p>
Note that this "intelligent passthrough" of network devices is
very similar to the functionality of a standard <hostdev>
device, the difference being that this method allows specifying
a MAC address and <virtualport> for the passed-through
device. If these capabilities are not required, if you have a
standard single-port PCI, PCIe, or USB network card that doesn't
support SR-IOV (and hence would anyway lose the configured MAC
address during reset after being assigned to the guest domain),
or if you are using a version of libvirt older than 0.9.11, you
should use standard <hostdev> to assign the device to the
guest instead of <interface type='hostdev'/>.
</p>
<pre>
...
<devices>
<interface type='hostdev'>
<source>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
</source>
<mac address='52:54:00:6d:90:02'>
<virtualport type='802.1Qbh'>
<parameters profileid='finance'/>
</virtualport>
</interface>
</devices>
...</pre>
<h5>
<a name="elementsNICSMulticast" id="elementsNICSMulticast">Multicast tunnel</a>
</h5>
<p>
A multicast group is setup to represent a virtual network. Any VMs
whose network devices are in the same multicast group can talk to each
other even across hosts. This mode is also available to unprivileged
users. There is no default DNS or DHCP support and no outgoing network
access. To provide outgoing network access, one of the VMs should have a
2nd NIC which is connected to one of the first 4 network types and do the
appropriate routing. The multicast protocol is compatible with that used
by user mode linux guests too. The source address used must be from the
multicast address block.
</p>
<pre>
...
<devices>
<interface type='mcast'>
<mac address='52:54:00:6d:90:01'>
<source address='230.0.0.1' port='5558'/>
</interface>
</devices>
...</pre>
<h5>
<a name="elementsNICSTCP" id="elementsNICSTCP">TCP tunnel</a>
</h5>
<p>
A TCP client/server architecture provides a virtual network. One VM
provides the server end of the network, all other VMS are configured as
clients. All network traffic is routed between the VMs via the server.
This mode is also available to unprivileged users. There is no default
DNS or DHCP support and no outgoing network access. To provide outgoing
network access, one of the VMs should have a 2nd NIC which is connected
to one of the first 4 network types and do the appropriate routing.</p>
<pre>
...
<devices>
<interface type='server'>
<mac address='52:54:00:22:c9:42'>
<source address='192.168.0.1' port='5558'/>
</interface>
...
<interface type='client'>
<mac address='52:54:00:8b:c9:51'>
<source address='192.168.0.1' port='5558'/>
</interface>
</devices>
...</pre>
<h5>
<a name="elementsNICSModel" id="elementsNICSModel">Setting the NIC model</a>
</h5>
<pre>
...
<devices>
<interface type='network'>
<source network='default'/>
<target dev='vnet1'/>
<b><model type='ne2k_pci'/></b>
</interface>
</devices>
...</pre>
<p>
For hypervisors which support this, you can set the model of
emulated network interface card.
</p>
<p>
The values for <code>type</code> aren't defined specifically by
libvirt, but by what the underlying hypervisor supports (if
any). For QEMU and KVM you can get a list of supported models
with these commands:
</p>
<pre>
qemu -net nic,model=? /dev/null
qemu-kvm -net nic,model=? /dev/null
</pre>
<p>
Typical values for QEMU and KVM include:
ne2k_isa i82551 i82557b i82559er ne2k_pci pcnet rtl8139 e1000 virtio
</p>
<h5>
<a name="elementsDriverBackendOptions" id="elementsDriverBackendOptions">Setting NIC driver-specific options</a>
</h5>
<pre>
...
<devices>
<interface type='network'>
<source network='default'/>
<target dev='vnet1'/>
<model type='virtio'/>
<b><driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off'/></b>
</interface>
</devices>
...</pre>
<p>
Some NICs may have tunable driver-specific options. These are
set as attributes of the <code>driver</code> sub-element of the
interface definition. Currently the following attributes are
available for the <code>"virtio"</code> NIC driver:
</p>
<dl><dt><code>name</code></dt><dd>
The optional <code>name</code> attribute forces which type of
backend driver to use. The value can be either 'qemu' (a
user-space backend) or 'vhost' (a kernel backend, which
requires the vhost module to be provided by the kernel); an
attempt to require the vhost driver without kernel support
will be rejected. If this attribute is not present, then the
domain defaults to 'vhost' if present, but silently falls back
to 'qemu' without error.
<span class="since">Since 0.8.8 (QEMU and KVM only)</span>
</dd><dt><code>txmode</code></dt><dd>
The <code>txmode</code> attribute specifies how to handle
transmission of packets when the transmit buffer is full. The
value can be either 'iothread' or 'timer'.
<span class="since">Since 0.8.8 (QEMU and KVM only)</span><br /><br />
If set to 'iothread', packet tx is all done in an iothread in
the bottom half of the driver (this option translates into
adding "tx=bh" to the qemu commandline -device virtio-net-pci
option).<br /><br />
If set to 'timer', tx work is done in qemu, and if there is
more tx data than can be sent at the present time, a timer is
set before qemu moves on to do other things; when the timer
fires, another attempt is made to send more data.<br /><br />
The resulting difference, according to the qemu developer who
added the option is: "bh makes tx more asynchronous and reduces
latency, but potentially causes more processor bandwidth
contention since the cpu doing the tx isn't necessarily the
cpu where the guest generated the packets."<br /><br /><b>In general you should leave this option alone, unless you
are very certain you know what you are doing.</b>
</dd><dt><code>ioeventfd</code></dt><dd>
This optional attribute allows users to set
<a href="https://patchwork.kernel.org/patch/43390/">
domain I/O asynchronous handling</a> for interface device.
The default is left to the discretion of the hypervisor.
Accepted values are "on" and "off". Enabling this allows
qemu to execute VM while a separate thread handles I/O.
Typically guests experiencing high system CPU utilization
during I/O will benefit from this. On the other hand,
on overloaded host it could increase guest I/O latency.
<span class="since">Since 0.9.3 (QEMU and KVM only)</span><br /><br /><b>In general you should leave this option alone, unless you
are very certain you know what you are doing.</b>
</dd><dt><code>event_idx</code></dt><dd>
The <code>event_idx</code> attribute controls some aspects of
device event processing. The value can be either 'on' or 'off'
- if it is on, it will reduce the number of interupts and
exits for the guest. The default is determined by QEMU;
usually if the feature is supported, default is on. In case
there is a situation where this behavior is suboptimal, this
attribute provides a way to force the feature off.
<span class="since">Since 0.9.5 (QEMU and KVM only)</span><br /><br /><b>In general you should leave this option alone, unless you
are very certain you know what you are doing.</b>
</dd></dl>
<h5>
<a name="elementsNICSTargetOverride" id="elementsNICSTargetOverride">Overriding the target element</a>
</h5>
<pre>
...
<devices>
<interface type='network'>
<source network='default'/>
<b><target dev='vnet1'/></b>
</interface>
</devices>
...</pre>
<p>
If no target is specified, certain hypervisors will
automatically generate a name for the created tun device. This
name can be manually specifed, however the name <i>must not
start with either 'vnet' or 'vif'</i>, which are prefixes
reserved by libvirt and certain hypervisors. Manually specified
targets using these prefixes will be ignored.
</p>
<h5>
<a name="elementsNICSBoot" id="elementsNICSBoot">Specifying boot order</a>
</h5>
<pre>
...
<devices>
<interface type='network'>
<source network='default'/>
<target dev='vnet1'/>
<b><boot order='1'/></b>
</interface>
</devices>
...</pre>
<p>
For hypervisors which support this, you can set a specific NIC to
be used for network boot. The <code>order</code> attribute determines
the order in which devices will be tried during boot sequence. The
per-device <code>boot</code> elements cannot be used together with
general boot elements in
<a href="#elementsOSBIOS">BIOS bootloader</a> section.
<span class="since">Since 0.8.8</span>
</p>
<h5>
<a name="elementsNICSROM" id="elementsNICSROM">Interface ROM BIOS configuration</a>
</h5>
<pre>
...
<devices>
<interface type='network'>
<source network='default'/>
<target dev='vnet1'/>
<b><rom bar='on' file='/etc/fake/boot.bin'/></b>
</interface>
</devices>
...</pre>
<p>
For hypervisors which support this, you can change how a PCI Network
device's ROM is presented to the guest. The <code>bar</code>
attribute can be set to "on" or "off", and determines whether
or not the device's ROM will be visible in the guest's memory
map. (In PCI documentation, the "rombar" setting controls the
presence of the Base Address Register for the ROM). If no rom
bar is specified, the qemu default will be used (older
versions of qemu used a default of "off", while newer qemus
have a default of "on").
The optional <code>file</code> attribute is used to point to a
binary file to be presented to the guest as the device's ROM
BIOS. This can be useful to provide an alternative boot ROM for a
network device.
<span class="since">Since 0.9.10 (QEMU and KVM only)</span>.
</p>
<h5>
<a name="elementQoS" id="elementQoS">Quality of service</a>
</h5>
<pre>
...
<devices>
<interface type='network'>
<source network='default'/>
<target dev='vnet0'/>
<b><bandwidth>
<inbound average='1000' peak='5000' burst='1024'/>
<outbound average='128' peak='256' burst='256'/>
</bandwidth></b>
</interface>
<devices>
...</pre>
<p>
This part of interface XML provides setting quality of service. Incoming
and outgoing traffic can be shaped independently. The
<code>bandwidth</code> element can have at most one <code>inbound</code>
and at most one <code>outbound</code> child elements. Leaving any of these
children element out result in no QoS applied on that traffic direction.
So, when you want to shape only domain's incoming traffic, use
<code>inbound</code> only, and vice versa. Each of these elements have one
mandatory attribute <code>average</code>. It specifies average bit rate on
interface being shaped. Then there are two optional attributes:
<code>peak</code>, which specifies maximum rate at which interface can send
data, and <code>burst</code>, amount of bytes that can be burst at
<code>peak</code> speed. Accepted values for attributes are integer
numbers. The units for <code>average</code> and <code>peak</code> attributes
are kilobytes per second, and for the <code>burst</code> just kilobytes.
<span class="since">Since 0.9.4</span>
</p>
<h5>
<a name="elementLink" id="elementLink">Modifying virtual link state</a>
</h5>
<pre>
...
<devices>
<interface type='network'>
<source network='default'/>
<target dev='vnet0'/>
<b><link state='down'/></b>
</interface>
<devices>
...</pre>
<p>
This element provides means of setting state of the virtual network link.
Possible values for attribute <code>state</code> are <code>up</code> and
<code>down</code>. If <code>down</code> is specified as the value, the interface
behaves as if it had the network cable disconnected. Default behavior if this
element is unspecified is to have the link state <code>up</code>.
<span class="since">Since 0.9.5</span>
</p>
<h4>
<a name="elementsInput" id="elementsInput">Input devices</a>
</h4>
<p>
Input devices allow interaction with the graphical framebuffer
in the guest virtual machine. When enabling the framebuffer, an
input device is automatically provided. It may be possible to
add additional devices explicitly, for example,
to provide a graphics tablet for absolute cursor movement.
</p>
<pre>
...
<devices>
<input type='mouse' bus='usb'/>
</devices>
...</pre>
<dl><dt><code>input</code></dt><dd>The <code>input</code> element has one mandatory attribute,
the <code>type</code> whose value can be either 'mouse' or
'tablet'. The latter provides absolute
cursor movement, while the former uses relative movement. The optional
<code>bus</code> attribute can be used to refine the exact device type.
It takes values "xen" (paravirtualized), "ps2" and "usb".</dd></dl>
<p>
The <code>input</code> element has an optional
sub-element <code><address></code> which can tie the
device to a particular PCI
slot, <a href="#elementsAddress">documented above</a>.
</p>
<h4>
<a name="elementsHub" id="elementsHub">Hub devices</a>
</h4>
<p>
A hub is a device that expands a single port into several so
that there are more ports available to connect devices to a host
system.
</p>
<pre>
...
<devices>
<hub type='usb'/>
</devices>
...</pre>
<dl><dt><code>hub</code></dt><dd>The <code>hub</code> element has one mandatory attribute,
the <code>type</code> whose value can only be 'usb'.</dd></dl>
<p>
The <code>hub</code> element has an optional
sub-element <code><address></code>
with <code>type='usb'</code>which can tie the device to a
particular controller, <a href="#elementsAddress">documented
above</a>.
</p>
<h4>
<a name="elementsGraphics" id="elementsGraphics">Graphical framebuffers</a>
</h4>
<p>
A graphics device allows for graphical interaction with the
guest OS. A guest will typically have either a framebuffer
or a text console configured to allow interaction with the
admin.
</p>
<pre>
...
<devices>
<graphics type='sdl' display=':0.0'/>
<graphics type='vnc' port='5904'>
<listen type='address' address='1.2.3.4'/>
</graphics>
<graphics type='rdp' autoport='yes' multiUser='yes' />
<graphics type='desktop' fullscreen='yes'/>
<graphics type='spice'>
<listen type='network' network='rednet'/>
</graphics>
</devices>
...</pre>
<dl><dt><code>graphics</code></dt><dd>The <code>graphics</code> element has a mandatory <code>type</code>
attribute which takes the value "sdl", "vnc", "rdp" or "desktop":
<dl><dt><code>"sdl"</code></dt><dd>
This displays a window on the host desktop, it can take 3
optional arguments: a <code>display</code> attribute for
the display to use, an <code>xauth</code> attribute for
the authentication identifier, and an
optional <code>fullscreen</code> attribute accepting
values 'yes' or 'no'.
</dd><dt><code>"vnc"</code></dt><dd>
Starts a VNC server. The <code>port</code> attribute
specifies the TCP port number (with -1 as legacy syntax
indicating that it should be
auto-allocated). The <code>autoport</code> attribute is
the new preferred syntax for indicating autoallocation of
the TCP port to use. The <code>listen</code> attribute is
an IP address for the server to listen
on. The <code>passwd</code> attribute provides a VNC
password in clear text. The <code>keymap</code> attribute
specifies the keymap to use. It is possible to set a limit
on the validity of the password be giving an
timestamp <code>passwdValidTo='2010-04-09T15:51:00'</code>
assumed to be in UTC. The <code>connected</code> attribute
allows control of connected client during password changes.
VNC accepts <code>keep</code> value only.
<span class="since">since 0.9.3</span>
NB, this may not be supported by all hypervisors.<br /><br />
Rather than using listen/port, QEMU supports a
<code>socket</code> attribute for listening on a unix
domain socket path.<span class="since">Since 0.8.8</span>
</dd><dt><code>"spice"</code></dt><dd>
<p>
Starts a SPICE server. The <code>port</code> attribute
specifies the TCP port number (with -1 as legacy syntax
indicating that it should be auto-allocated),
while <code>tlsPort</code> gives an alternative secure
port number. The <code>autoport</code> attribute is the
new preferred syntax for indicating autoallocation of
both port numbers. The <code>listen</code> attribute is
an IP address for the server to listen
on. The <code>passwd</code> attribute provides a SPICE
password in clear text. The <code>keymap</code>
attribute specifies the keymap to use. It is possible to
set a limit on the validity of the password be giving an
timestamp <code>passwdValidTo='2010-04-09T15:51:00'</code>
assumed to be in UTC. The <code>connected</code> attribute
allows control of connected client during password changes.
SPICE accepts <code>keep</code> to keep client connected,
<code>disconnect</code> to disconnect client and
<code>fail</code> to fail changing password.
<span class="since">Since 0.9.3</span>
NB, this may not be supported by all hypervisors.
<span class="since">"spice" since 0.8.6</span>.
The <code>defaultMode</code> attribute sets the default channel
security policy, valid values are <code>secure</code>,
<code>insecure</code> and the default <code>any</code>
(which is secure if possible, but falls back to insecure
rather than erroring out if no secure path is
available). <span class="since">"defaultMode" since
0.9.12</span>.
</p>
<p>
When SPICE has both a normal and TLS secured TCP port
configured, it can be desirable to restrict what
channels can be run on each port. This is achieved by
adding one or more <channel> elements inside the
main <graphics> element. Valid channel names
include <code>main</code>, <code>display</code>,
<code>inputs</code>, <code>cursor</code>,
<code>playback</code>, <code>record</code>
(all <span class="since"> since 0.8.6</span>);
<code>smartcard</code> (<span class="since">since
0.8.8</span>); and <code>usbredir</code>
(<span class="since">since 0.9.12</span>).
</p>
<pre>
<graphics type='spice' port='-1' tlsPort='-1' autoport='yes'>
<channel name='main' mode='secure'/>
<channel name='record' mode='insecure'/>
<image compression='auto_glz'/>
<streaming mode='filter'/>
<clipboard copypaste='no'/>
<mouse mode='client'/>
</graphics></pre>
<p>
Spice supports variable compression settings for audio,
images and streaming, <span class="since">since
0.9.1</span>. These settings are accessible via
the <code>compression</code> attribute in all following
elements: <code>image</code> to set image compression
(accepts <code>auto_glz</code>, <code>auto_lz</code>,
<code>quic</code>, <code>glz</code>, <code>lz</code>,
<code>off</code>), <code>jpeg</code> for JPEG
compression for images over wan
(accepts <code>auto</code>, <code>never</code>,
<code>always</code>), <code>zlib</code> for configuring
wan image compression (accepts <code>auto</code>,
<code>never</code>, <code>always</code>)
and <code>playback</code> for enabling audio stream
compression (accepts <code>on</code> or <code>off</code>).
</p>
<p>
Streaming mode is set by the <code>streaming</code>
element, settings its <code>mode</code> attribute to one
of <code>filter</code>, <code>all</code>
or <code>off</code>, <span class="since">since 0.9.2</span>.
</p>
<p>
Copy & Paste functionality (via Spice agent) is set
by the <code>clipboard</code> element. It is enabled by
default, and can be disabled by setting
the <code>copypaste</code> property
to <code>no</code>, <span class="since">since
0.9.3</span>.
</p>
<p>
Mouse mode is set by the <code>mouse</code> element,
setting its <code>mode</code> attribute to one of
<code>server</code> or <code>client</code> ,
<span class="since">since 0.9.11</span>. If no mode is
specified, the qemu default will be used (client mode).
</p>
</dd><dt><code>"rdp"</code></dt><dd>
Starts a RDP server. The <code>port</code> attribute
specifies the TCP port number (with -1 as legacy syntax
indicating that it should be
auto-allocated). The <code>autoport</code> attribute is
the new preferred syntax for indicating autoallocation of
the TCP port to use. The <code>replaceUser</code>
attribute is a boolean deciding whether multiple
simultaneous connections to the VM are permitted.
The <code>multiUser</code> whether the existing connection
must be dropped and a new connection must be established
by the VRDP server, when a new client connects in single
connection mode.
</dd><dt><code>"desktop"</code></dt><dd>
This value is reserved for VirtualBox domains for the
moment. It displays a window on the host desktop,
similarly to "sdl", but using the VirtualBox viewer. Just
like "sdl", it accepts the optional
attributes <code>display</code>
and <code>fullscreen</code>.
</dd></dl></dd></dl>
<p>
Rather than putting the address information used to set up the
listening socket for graphics types <code>vnc</code>
and <code>spice</code> in
the <code><graphics></code> <code>listen</code> attribute,
a separate subelement of <code><graphics></code>,
called <code><listen></code> can be specified (see the
examples above)<span class="since">since
0.9.4</span>. <code><listen></code> accepts the following
attributes:
</p>
<dl><dt><code>type</code></dt><dd>Set to either <code>address</code>
or <code>network</code>. This tells whether this listen
element is specifying the address to be used directly, or by
naming a network (which will then be used to determine an
appropriate address for listening).
</dd></dl>
<dl><dt><code>address</code></dt><dd>if <code>type='address'</code>, the <code>address</code>
attribute will contain either an IP address or hostname (which
will be resolved to an IP address via a DNS query) to listen
on. In the "live" XML of a running domain, this attribute will
be set to the IP address used for listening, even
if <code>type='network'</code>.
</dd></dl>
<dl><dt><code>network</code></dt><dd>if <code>type='network'</code>, the <code>network</code>
attribute will contain the name of a network in libvirt's list
of configured networks. The named network configuration will
be examined to determine an appropriate listen address. For
example, if the network has an IPv4 address in its
configuration (e.g. if it has a forward type
of <code>route</code>, <code>nat</code>, or no forward type
(isolated)), the first IPv4 address listed in the network's
configuration will be used. If the network is describing a
host bridge, the first IPv4 address associated with that
bridge device will be used, and if the network is describing
one of the 'direct' (macvtap) modes, the first IPv4 address of
the first forward dev will be used.
</dd></dl>
<h4>
<a name="elementsVideo" id="elementsVideo">Video devices</a>
</h4>
<p>
A video device.
</p>
<pre>
...
<devices>
<video>
<model type='vga' vram='8192' heads='1'>
<acceleration accel3d='yes' accel2d='yes'/>
</model>
</video>
</devices>
...</pre>
<dl><dt><code>video</code></dt><dd>
The <code>video</code> element is the container for describing
video devices. For backwards compatibility, if no <code>video</code>
is set but there is a <code>graphics</code> in domain xml, then libvirt
will add a default <code>video</code> according to the guest type.
For a guest of type "kvm", the default <code>video</code> for it is:
<code>type</code> with value "cirrus", <code>vram</code> with value
"9216", and <code>heads</code> with value "1".
</dd><dt><code>model</code></dt><dd>
The <code>model</code> element has a mandatory <code>type</code>
attribute which takes the value "vga", "cirrus", "vmvga", "xen",
"vbox", or "qxl" (<span class="since">since 0.8.6</span>)
depending on the hypervisor features available.
You can also provide the amount of video memory in kibibytes
(blocks of 1024 bytes) using
<code>vram</code> and the number of screen with <code>heads</code>.
</dd><dt><code>acceleration</code></dt><dd>
If acceleration should be enabled (if supported) using the
<code>accel3d</code> and <code>accel2d</code> attributes in the
<code>acceleration</code> element.
</dd><dt><code>address</code></dt><dd>
The optional <code>address</code> sub-element can be used to
tie the video device to a particular PCI slot.
</dd></dl>
<h4>
<a name="elementsConsole" id="elementsConsole">Consoles, serial, parallel & channel devices</a>
</h4>
<p>
A character device provides a way to interact with the virtual machine.
Paravirtualized consoles, serial ports, parallel ports and channels are
all classed as character devices and so represented using the same syntax.
</p>
<pre>
...
<devices>
<parallel type='pty'>
<source path='/dev/pts/2'/>
<target port='0'/>
</parallel>
<serial type='pty'>
<source path='/dev/pts/3'/>
<target port='0'/>
</serial>
<console type='pty'>
<source path='/dev/pts/4'/>
<target port='0'/>
</console>
<channel type='unix'>
<source mode='bind' path='/tmp/guestfwd'/>
<target type='guestfwd' address='10.0.2.1' port='4600'/>
</channel>
</devices>
...</pre>
<p>
In each of these directives, the top-level element name (parallel, serial,
console, channel) describes how the device is presented to the guest. The
guest interface is configured by the <code>target</code> element.
</p>
<p>
The interface presented to the host is given in the <code>type</code>
attribute of the top-level element. The host interface is
configured by the <code>source</code> element.
</p>
<p>
Each character device element has an optional
sub-element <code><address></code> which can tie the
device to a
particular <a href="#elementsControllers">controller</a> or PCI
slot.
</p>
<h5>
<a name="elementsCharGuestInterface" id="elementsCharGuestInterface">Guest interface</a>
</h5>
<p>
A character device presents itself to the guest as one of the following
types.
</p>
<h6>
<a name="elementCharParallel" id="elementCharParallel">Parallel port</a>
</h6>
<pre>
...
<devices>
<parallel type='pty'>
<source path='/dev/pts/2'/>
<target port='0'/>
</parallel>
</devices>
...</pre>
<p>
<code>target</code> can have a <code>port</code> attribute, which
specifies the port number. Ports are numbered starting from 0. There are
usually 0, 1 or 2 parallel ports.
</p>
<h6>
<a name="elementCharSerial" id="elementCharSerial">Serial port</a>
</h6>
<pre>
...
<devices>
<serial type='pty'>
<source path='/dev/pts/3'/>
<target port='0'/>
</serial>
</devices>
...</pre>
<p>
<code>target</code> can have a <code>port</code> attribute, which
specifies the port number. Ports are numbered starting from 0. There are
usually 0, 1 or 2 serial ports.
</p>
<h6>
<a name="elementCharConsole" id="elementCharConsole">Console</a>
</h6>
<p>
The console element is used to represent interactive consoles. Depending
on the type of guest in use, the consoles might be paravirtualized devices,
or they might be a clone of a serial device, according to the following
rules:
</p>
<ul><li>If no <code>targetType</code> attribue is set, then the default
device type is according to the hypervisor's rules. The default
type will be added when re-querying the XML fed into libvirt.
For fully virtualized guests, the default device type will usually
be a serial port.</li><li>If the <code>targetType</code> attribute is <code>serial</code>,
then if no <code><serial></code> element exists, the console
element will be copied to the serial element. If a <code><serial></code>
element does already exist, the console element will be ignored.</li><li>If the <code>targetType</code> attribute is not <code>serial</code>,
it will be treated normally.</li><li>Only the first <code>console</code> element may use a <code>targetType</code>
of <code>serial</code>. Secondary consoles must all be paravirtualized.
</li></ul>
<p>
A virtio console device is exposed in the
guest as /dev/hvc[0-7] (for more information, see
<a href="http://fedoraproject.org/wiki/Features/VirtioSerial">http://fedoraproject.org/wiki/Features/VirtioSerial</a>)
<span class="since">Since 0.8.3</span>
</p>
<pre>
...
<devices>
<console type='pty'>
<source path='/dev/pts/4'/>
<target port='0'/>
</console>
<!-- KVM virtio console -->
<console type='pty'>
<source path='/dev/pts/5'/>
<target type='virtio' port='0'/>
</console>
</devices>
...</pre>
<p>
If the console is presented as a serial port, the <code>target</code>
element has the same attributes as for a serial port. There is usually
only 1 console.
</p>
<h6>
<a name="elementCharChannel" id="elementCharChannel">Channel</a>
</h6>
<p>
This represents a private communication channel between the host and the
guest.
</p>
<pre>
...
<devices>
<channel type='unix'>
<source mode='bind' path='/tmp/guestfwd'/>
<target type='guestfwd' address='10.0.2.1' port='4600'/>
</channel>
<!-- KVM virtio channel -->
<channel type='pty'>
<target type='virtio' name='arbitrary.virtio.serial.port.name'/>
</channel>
<channel type='unix'>
<source mode='bind' path='/var/lib/libvirt/qemu/f16x86_64.agent'/>
<target type='virtio' name='org.qemu.guest_agent.0'/>
</channel>
<channel type='spicevmc'>
<target type='virtio' name='com.redhat.spice.0'/>
</channel>
</devices>
...</pre>
<p>
This can be implemented in a variety of ways. The specific type of
channel is given in the <code>type</code> attribute of the
<code>target</code> element. Different channel types have different
<code>target</code> attributes.
</p>
<dl><dt><code>guestfwd</code></dt><dd>TCP traffic sent by the guest to a given IP address and port is
forwarded to the channel device on the host. The <code>target</code>
element must have <code>address</code> and <code>port</code> attributes.
<span class="since">Since 0.7.3</span></dd><dt><code>virtio</code></dt><dd>Paravirtualized virtio channel. Channel is exposed in the guest under
/dev/vport*, and if the optional element <code>name</code> is specified,
/dev/virtio-ports/$name (for more info, please see
<a href="http://fedoraproject.org/wiki/Features/VirtioSerial">http://fedoraproject.org/wiki/Features/VirtioSerial</a>). The
optional element <code>address</code> can tie the channel to a
particular <code>type='virtio-serial'</code>
controller, <a href="#elementsAddress">documented above</a>.
With qemu, if <code>name</code> is "org.qemu.guest_agent.0",
then libvirt can interact with a guest agent installed in the
guest, for actions such as guest shutdown or file system quiescing.
<span class="since">Since 0.7.7, guest agent interaction
since 0.9.10</span></dd><dt><code>spicevmc</code></dt><dd>Paravirtualized SPICE channel. The domain must also have a
SPICE server as a <a href="#elementsGraphics">graphics
device</a>, at which point the host piggy-backs messages
across the <code>main</code> channel. The <code>target</code>
element must be present, with
attribute <code>type='virtio'</code>; an optional
attribute <code>name</code> controls how the guest will have
access to the channel, and defaults
to <code>name='com.redhat.spice.0'</code>. The
optional <code>address</code> element can tie the channel to a
particular <code>type='virtio-serial'</code> controller.
<span class="since">Since 0.8.8</span></dd></dl>
<h5>
<a name="elementsCharHostInterface" id="elementsCharHostInterface">Host interface</a>
</h5>
<p>
A character device presents itself to the host as one of the following
types.
</p>
<h6>
<a name="elementsCharSTDIO" id="elementsCharSTDIO">Domain logfile</a>
</h6>
<p>
This disables all input on the character device, and sends output
into the virtual machine's logfile
</p>
<pre>
...
<devices>
<console type='stdio'>
<target port='1'/>
</console>
</devices>
...</pre>
<h6>
<a name="elementsCharFle" id="elementsCharFle">Device logfile</a>
</h6>
<p>
A file is opened and all data sent to the character
device is written to the file.
</p>
<pre>
...
<devices>
<serial type="file">
<source path="/var/log/vm/vm-serial.log"/>
<target port="1"/>
</serial>
</devices>
...</pre>
<h6>
<a name="elementsCharVC" id="elementsCharVC">Virtual console</a>
</h6>
<p>
Connects the character device to the graphical framebuffer in
a virtual console. This is typically accessed via a special
hotkey sequence such as "ctrl+alt+3"
</p>
<pre>
...
<devices>
<serial type='vc'>
<target port="1"/>
</serial>
</devices>
...</pre>
<h6>
<a name="elementsCharNull" id="elementsCharNull">Null device</a>
</h6>
<p>
Connects the character device to the void. No data is ever
provided to the input. All data written is discarded.
</p>
<pre>
...
<devices>
<serial type='null'>
<target port="1"/>
</serial>
</devices>
...</pre>
<h6>
<a name="elementsCharPTY" id="elementsCharPTY">Pseudo TTY</a>
</h6>
<p>
A Pseudo TTY is allocated using /dev/ptmx. A suitable client
such as 'virsh console' can connect to interact with the
serial port locally.
</p>
<pre>
...
<devices>
<serial type="pty">
<source path="/dev/pts/3"/>
<target port="1"/>
</serial>
</devices>
...</pre>
<p>
NB special case if <console type='pty'>, then the TTY
path is also duplicated as an attribute tty='/dev/pts/3'
on the top level <console> tag. This provides compat
with existing syntax for <console> tags.
</p>
<h6>
<a name="elementsCharHost" id="elementsCharHost">Host device proxy</a>
</h6>
<p>
The character device is passed through to the underlying
physical character device. The device types must match,
eg the emulated serial port should only be connected to
a host serial port - don't connect a serial port to a parallel
port.
</p>
<pre>
...
<devices>
<serial type="dev">
<source path="/dev/ttyS0"/>
<target port="1"/>
</serial>
</devices>
...</pre>
<h6>
<a name="elementsCharPipe" id="elementsCharPipe">Named pipe</a>
</h6>
<p>
The character device writes output to a named pipe. See pipe(7) for
more info.
</p>
<pre>
...
<devices>
<serial type="pipe">
<source path="/tmp/mypipe"/>
<target port="1"/>
</serial>
</devices>
...</pre>
<h6>
<a name="elementsCharTCP" id="elementsCharTCP">TCP client/server</a>
</h6>
<p>
The character device acts as a TCP client connecting to a
remote server.
</p>
<pre>
...
<devices>
<serial type="tcp">
<source mode="connect" host="0.0.0.0" service="2445"/>
<protocol type="raw"/>
<target port="1"/>
</serial>
</devices>
...</pre>
<p>
Or as a TCP server waiting for a client connection.
</p>
<pre>
...
<devices>
<serial type="tcp">
<source mode="bind" host="127.0.0.1" service="2445"/>
<protocol type="raw"/>
<target port="1"/>
</serial>
</devices>
...</pre>
<p>
Alternatively you can use <code>telnet</code> instead
of <code>raw</code> TCP. <span class="since">Since 0.8.5</span>
you can also use <code>telnets</code>
(secure telnet) and <code>tls</code>.
</p>
<pre>
...
<devices>
<serial type="tcp">
<source mode="connect" host="0.0.0.0" service="2445"/>
<protocol type="telnet"/>
<target port="1"/>
</serial>
...
<serial type="tcp">
<source mode="bind" host="127.0.0.1" service="2445"/>
<protocol type="telnet"/>
<target port="1"/>
</serial>
</devices>
...</pre>
<h6>
<a name="elementsCharUDP" id="elementsCharUDP">UDP network console</a>
</h6>
<p>
The character device acts as a UDP netconsole service,
sending and receiving packets. This is a lossy service.
</p>
<pre>
...
<devices>
<serial type="udp">
<source mode="bind" host="0.0.0.0" service="2445"/>
<source mode="connect" host="0.0.0.0" service="2445"/>
<target port="1"/>
</serial>
</devices>
...</pre>
<h6>
<a name="elementsCharUNIX" id="elementsCharUNIX">UNIX domain socket client/server</a>
</h6>
<p>
The character device acts as a UNIX domain socket server,
accepting connections from local clients.
</p>
<pre>
...
<devices>
<serial type="unix">
<source mode="bind" path="/tmp/foo"/>
<target port="1"/>
</serial>
</devices>
...</pre>
<h4>
<a name="elementsSound" id="elementsSound">Sound devices</a>
</h4>
<p>
A virtual sound card can be attached to the host via the
<code>sound</code> element. <span class="since">Since 0.4.3</span>
</p>
<pre>
...
<devices>
<sound model='es1370'/>
</devices>
...</pre>
<dl><dt><code>sound</code></dt><dd>
The <code>sound</code> element has one mandatory attribute,
<code>model</code>, which specifies what real sound device is emulated.
Valid values are specific to the underlying hypervisor, though typical
choices are 'es1370', 'sb16', 'ac97', and 'ich6'
(<span class="since">
'ac97' only since 0.6.0, 'ich6' only since 0.8.8</span>)
</dd></dl>
<p>
Each <code>sound</code> element has an optional
sub-element <code><address></code> which can tie the
device to a particular PCI
slot, <a href="#elementsAddress">documented above</a>.
</p>
<h4>
<a name="elementsWatchdog" id="elementsWatchdog">Watchdog device</a>
</h4>
<p>
A virtual hardware watchdog device can be added to the guest via
the <code>watchdog</code> element.
<span class="since">Since 0.7.3, QEMU and KVM only</span>
</p>
<p>
The watchdog device requires an additional driver and management
daemon in the guest. Just enabling the watchdog in the libvirt
configuration does not do anything useful on its own.
</p>
<p>
Currently libvirt does not support notification when the
watchdog fires. This feature is planned for a future version of
libvirt.
</p>
<pre>
...
<devices>
<watchdog model='i6300esb'/>
</devices>
...</pre>
<pre>
...
<devices>
<watchdog model='i6300esb' action='poweroff'/>
</devices>
</domain></pre>
<dl><dt><code>model</code></dt><dd>
<p>
The required <code>model</code> attribute specifies what real
watchdog device is emulated. Valid values are specific to the
underlying hypervisor.
</p>
<p>
QEMU and KVM support:
</p>
<ul><li> 'i6300esb' — the recommended device,
emulating a PCI Intel 6300ESB </li><li> 'ib700' — emulating an ISA iBase IB700 </li></ul></dd><dt><code>action</code></dt><dd>
<p>
The optional <code>action</code> attribute describes what
action to take when the watchdog expires. Valid values are
specific to the underlying hypervisor.
</p>
<p>
QEMU and KVM support:
</p>
<ul><li>'reset' — default, forcefully reset the guest</li><li>'shutdown' — gracefully shutdown the guest
(not recommended) </li><li>'poweroff' — forcefully power off the guest</li><li>'pause' — pause the guest</li><li>'none' — do nothing</li><li>'dump' — automatically dump the guest
<span class="since">Since 0.8.7</span></li></ul><p>
Note 1: the 'shutdown' action requires that the guest
is responsive to ACPI signals. In the sort of situations
where the watchdog has expired, guests are usually unable
to respond to ACPI signals. Therefore using 'shutdown'
is not recommended.
</p>
<p>
Note 2: the directory to save dump files can be configured
by <code>auto_dump_path</code> in file /etc/libvirt/qemu.conf.
</p>
</dd></dl>
<h4>
<a name="elementsMemBalloon" id="elementsMemBalloon">Memory balloon device</a>
</h4>
<p>
A virtual memory balloon device is added to all Xen and KVM/QEMU
guests. It will be seen as <code>memballoon</code> element.
It will be automatically added when appropriate, so there is no
need to explicitly add this element in the guest XML unless a
specific PCI slot needs to be assigned.
<span class="since">Since 0.8.3, Xen, QEMU and KVM only</span>
Additionally, <span class="since">since 0.8.4</span>, if the
memballoon device needs to be explicitly disabled,
<code>model='none'</code> may be used.
</p>
<p>
Example automatically added device with KVM
</p>
<pre>
...
<devices>
<memballoon model='virtio'/>
</devices>
...</pre>
<p>
Example manually added device with static PCI slot 2 requested
</p>
<pre>
...
<devices>
<watchdog model='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</devices>
</domain></pre>
<dl><dt><code>model</code></dt><dd>
<p>
The required <code>model</code> attribute specifies what type
of balloon device is provided. Valid values are specific to
the virtualization platform
</p>
<ul><li>'virtio' — default with QEMU/KVM</li><li>'xen' — default with Xen</li></ul></dd></dl>
<h3>
<a name="seclabel" id="seclabel">Security label</a>
</h3>
<p>
The <code>seclabel</code> element allows control over the
operation of the security drivers. There are three basic
modes of operation, 'dynamic' where libvirt automatically
generates a unique security label, 'static' where the
application/administrator chooses the labels, or 'none'
where confinement is disabled. With dynamic
label generation, libvirt will always automatically
relabel any resources associated with the virtual machine.
With static label assignment, by default, the administrator
or application must ensure labels are set correctly on any
resources, however, automatic relabeling can be enabled
if desired. <span class="since">'dynamic' since 0.6.1, 'static'
since 0.6.2, and 'none' since 0.9.10.</span>
</p>
<p>
Valid input XML configurations for the top-level security label
are:
</p>
<pre>
<seclabel type='dynamic' model='selinux'/>
<seclabel type='dynamic' model='selinux'>
<baselabel>system_u:system_r:my_svirt_t:s0</baselabel>
</seclabel>
<seclabel type='static' model='selinux' relabel='no'>
<label>system_u:system_r:svirt_t:s0:c392,c662</label>
</seclabel>
<seclabel type='static' model='selinux' relabel='yes'>
<label>system_u:system_r:svirt_t:s0:c392,c662</label>
</seclabel>
<seclabel type='none'/>
</pre>
<p>
If no 'type' attribute is provided in the input XML, then
the security driver default setting will be used, which
may be either 'none' or 'dynamic'. If a 'baselabel' is set
but no 'type' is set, then the type is presumed to be 'dynamic'
</p>
<p>
When viewing the XML for a running guest with automatic
resource relabeling active, an additional XML element,
<code>imagelabel</code>, will be included. This is an
output-only element, so will be ignored in user supplied
XML documents
</p>
<dl><dt><code>type</code></dt><dd>Either <code>static</code>, <code>dynamic</code> or <code>none</code>
to determine whether libvirt automatically generates a unique security
label or not.
</dd><dt><code>model</code></dt><dd>A valid security model name, matching the currently
activated security model
</dd><dt><code>relabel</code></dt><dd>Either <code>yes</code> or <code>no</code>. This must always
be <code>yes</code> if dynamic label assignment is used. With
static label assignment it will default to <code>no</code>.
</dd><dt><code>label</code></dt><dd>If static labelling is used, this must specify the full
security label to assign to the virtual domain. The format
of the content depends on the security driver in use
</dd><dt><code>baselabel</code></dt><dd>If dynamic labelling is used, this can optionally be
used to specify the base security label. The format
of the content depends on the security driver in use
</dd><dt><code>imagelabel</code></dt><dd>This is an output only element, which shows the
security label used on resources associated with the virtual domain.
The format of the content depends on the security driver in use
</dd></dl>
<p>When relabeling is in effect, it is also possible to fine-tune
the labeling done for specific source file names, by either
disabling the labeling (useful if the file lives on NFS or other
file system that lacks security labeling) or requesting an
alternate label (useful when a management application creates a
special label to allow sharing of some, but not all, resources
between domains), <span class="since">since 0.9.9</span>. When
a <code>seclabel</code> element is attached to a specific path
rather than the top-level domain assignment, only the
attribute <code>relabel</code> or the
sub-element <code>label</code> are supported.
</p>
<h2>
<a name="examples" id="examples">Example configs</a>
</h2>
<p>
Example configurations for each driver are provide on the
driver specific pages listed below
</p>
<ul><li><a href="drvxen.html#xmlconfig">Xen examples</a></li><li><a href="drvqemu.html#xmlconfig">QEMU/KVM examples</a></li></ul>
</div>
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