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 driver docs
The root element required for all virtual machines is
named domain
. It has two attributes, the
type
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 id
which is a unique
integer identifier for the running guest machine. Inactive
machines have no id value.
<domain type='xen' id='3'> <name>fv0</name> <uuid>4dea22b31d52d8f32516782e98ab3fa0</uuid> <description>Some human readable description</description> ...
name
name
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. Since 0.0.1uuid
uuid
element provides
a globally unique identifier for the virtual machine.
The format must be RFC 4122 compliant,
eg 3e3fce45-4f53-4fa7-bb32-11f34168b82b
.
If omitted when defining/creating a new machine, a random
UUID is generated. It is also possible to provide the UUID
via a sysinfo
specification. Since 0.0.1, sysinfo
since 0.8.7description
description
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. Since 0.7.2There are a number of different ways to boot virtual machines each with their own pros and cons.
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.
... <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> ...
type
type
element specifies the
type of operating system to be booted in the virtual machine.
hvm
indicates that the OS is one designed to run
on bare metal, so requires full virtualization. linux
(badly named!) refers to an OS that supports the Xen 3 hypervisor
guest ABI. There are also two optional attributes, arch
specifying the CPU architecture to virtualization,
and machine
referring to the machine
type. The Capabilities XML
provides details on allowed values for
these. Since 0.0.1loader
loader
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. Since 0.1.0boot
dev
attribute takes one of the values "fd", "hd",
"cdrom" or "network" and is used to specify the next boot device
to consider. The boot
element can be repeated multiple
times to setup a priority list of boot devices to try in turn. The
boot
element cannot be used if per-device boot elements
are used (see disks,
network interfaces, and
USB and PCI devices sections below).
Since 0.1.3, per-device boot since 0.8.8
bootmenu
enable
attribute can be either "yes" or "no".
If not specified, the hypervisor default is used.
Since 0.8.3
smbios
mode
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
virConnectGetSysinfo
call can be
used to see what values are copied), or "sysinfo" (use the values in
the sysinfo element). If not
specified, the hypervisor default is used.
Since 0.8.7
bios
useserial
with possible
values yes
or no
. It enables or disables
Serial Graphics Adapter which allows users to see BIOS messages
on a serial port. Therefore, one needs to have
serial port defined.
Since 0.9.4
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 pygrub
with Xen.
... <bootloader>/usr/bin/pygrub</bootloader> <bootloader_args>--append single</bootloader_args> ...
bootloader
bootloader
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. Since 0.1.0bootloader_args
bootloader_args
element allows
command line arguments to be passed to the bootloader.
Since 0.2.3
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.
... <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> ...
type
loader
kernel
initrd
cmdline
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 dmidecode
command in the guest). The
optional sysinfo
element covers all such categories
of information. Since 0.8.7
... <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> ...
The sysinfo
element has a mandatory
attribute type
that determine the layout of
sub-elements, with supported values of:
smbios
smbios
sub-element of
the os
element. Each
sub-element of sysinfo
names a SMBIOS block, and
within those elements can be a list of entry
elements that describe a field within the block. The following
blocks and entries are recognized:
bios
system
uuid
element, the two values must match.
<domain> ... <vcpu cpuset="1-4,^3,6" current="1">2</vcpu> ... </domain>
vcpu
cpuset
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. Since
0.8.5, the optional attribute current
can
be used to specify whether fewer than the maximum number of
virtual CPUs should be enabled.
<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>
cputune
cputune
element provides details
regarding the cpu tunable parameters for the domain.
Since 0.9.0
vcpupin
vcpupin
element specifies which of host
physical CPUS the domain VCPU will be pinned to. If this is ommited,
each VCPU pinned to all the physical CPUS by default. It contains two
required attributes, the attribute vcpu
specifies vcpu id,
and the attribute cpuset
is same as
attribute cpuset
of element vcpu
. (NB: Only qemu driver support)
Since 0.9.0
shares
shares
element specifies the proportional
weighted share for the domain. If this is ommited, 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.
Since 0.9.0
period
period
element specifies the enforcement
interval(unit: microseconds). Within period
, each vcpu of
the domain will not be allowed to consume more than quota
worth of runtime. The value should be in range [1000, 1000000]. A period
with value 0 means no value. (NB: Only qemu driver support)
Since 0.9.4
quota
quota
element specifies the maximum allowed
bandwidth(unit: microseconds). A domain with quota
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)
Since 0.9.4
<domain> ... <memory>524288</memory> <currentMemory>524288</currentMemory> ... </domain>
memory
currentMemory
memory
element<domain> ... <memoryBacking> <hugepages/> </memoryBacking> ... </domain>
memoryBacking
memoryBacking
element, may have an
hugepages
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.<domain> ... <memtune> <hard_limit>1048576</hard_limit> <soft_limit>131072</soft_limit> <swap_hard_limit>2097152</swap_hard_limit> <min_guarantee>65536</min_guarantee> </memtune> ... </domain>
memtune
memtune
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.hard_limit
hard_limit
element is the maximum memory
the guest can use. The units for this value are kilobytes (i.e. blocks
of 1024 bytes)soft_limit
soft_limit
element is the memory limit to
enforce during memory contention. The units for this value are
kilobytes (i.e. blocks of 1024 bytes)swap_hard_limit
swap_hard_limit
element is the maximum
memory plus swap the guest can use. The units for this value are
kilobytes (i.e. blocks of 1024 bytes). This has to be more than
hard_limit value providedmin_guarantee
min_guarantee
element is the guaranteed
minimum memory allocation for the guest. The units for this value are
kilobytes (i.e. blocks of 1024 bytes)<domain> ... <numatune> <memory mode="strict" nodeset="1-4,^3"/> </numatune> ... </domain>
numatune
numatune
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.
Since 0.9.3
memory
memory
element specify how to allocate memory
for the domain process on a NUMA host. It contains two attributes,
attribute mode
is either 'interleave', 'strict',
or 'preferred',
attribute nodeset
specifies the NUMA nodes, it leads same
syntax with attribute cpuset
of element vcpu
.
Since 0.9.3
<domain> ... <blkiotune> <weight>800</weight> </blkiotune> ... </domain>
blkiotune
blkiotune
element provides the ability
to tune Blkio cgroup tunable parameters for the domain. If this is
omitted, it defaults to the OS provided defaults.weight
weight
element is the I/O weight of the
guest. The value should be in range [100, 1000].Requirements for CPU model, its features and topology can be specified using the following collection of elements. Since 0.7.5
... <cpu match='exact'> <model>core2duo</model> <vendor>Intel</vendor> <topology sockets='1' cores='2' threads='1'/> <feature policy='disable' name='lahf_lm'/> </cpu> ...
In case no restrictions need to be put on CPU model and its features, a
simpler cpu
element can be used.
Since 0.7.6
... <cpu> <topology sockets='1' cores='2' threads='1'/> </cpu> ...
cpu
cpu
element is the main container for describing
guest CPU requirements. Its match
attribute specified how
strictly has the virtual CPU provided to the guest match these
requirements. Since 0.7.6 the
match
attribute can be omitted if topology
is the only element within cpu
. Possible values for the
match
attribute are:
minimum
exact
strict
match
attribute can be omitted and will default to exact
.
model
model
element specifies CPU model
requested by the guest. The list of available CPU models and their
definition can be found in cpu_map.xml
file installed
in libvirt's data directory.vendor
vendor
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 cpu_map.xml
.topology
topology
element specifies requested topology of
virtual CPU provided to the guest. Three non-zero values have to be
given for sockets
, cores
, and
threads
: total number of CPU sockets, number of cores per
socket, and number of threads per core, respectively.feature
cpu
element can contain zero or more
elements
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 feature
element depends on its policy
attribute, which has to be
set to one of the following values:
force
require
optional
disable
forbid
policy
attribute can be omitted and will default to require
.
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.
... <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> ...
on_poweroff
on_reboot
on_crash
Each of these states allow for the same four possible actions.
destroy
restart
preserve
rename-restart
on_crash supports these additional actions since 0.8.4.
coredump-destroy
coredump-restart
Hypervisors may allow certain CPU / machine features to be toggled on/off.
... <features> <pae/> <acpi/> <apic/> <hap/> </features> ...
All features are listed within the features
element, omitting a togglable feature tag turns it off.
The available features can be found by asking
for the capabilities XML,
but a common set for fully virtualized domains are:
pae
acpi
hap
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'.
... <clock offset="localtime"> <timer name="rtc" tickpolicy="catchup" track="guest"> <catchup threshold=123 slew=120 limit=10000/> </timer> <timer name="pit" tickpolicy="delay"/> </clock> ...
clock
The offset
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.
utc
localtime
timezone
timezone
attribute.
Since 0.7.7
variable
adjustment
attribute.
The guest is free to adjust the RTC over time and expect
that it will be honoured at next reboot. This is in
contrast to 'utc' mode, where the RTC adjustments are
lost at each reboot. Since 0.7.7
A clock
may have zero or more
timer
sub-elements. Since
0.8.0
timer
Each timer element requires a name
attribute,
and has other optional attributes that depend on
the name
specified. Various hypervisors
support different combinations of attributes.
name
name
attribute selects which timer is
being modified, and can be one of "platform", "pit",
"rtc", "hpet", or "tsc".
track
track
attribute specifies what the timer
tracks, and can be "boot", "guest", or "wall".
Only valid for name="rtc"
or name="platform"
.
tickpolicy
tickpolicy
attribute determines how
missed ticks in the guest are handled, and can be "delay",
"catchup", "merge", or "discard". If the policy is
"catchup", there can be further details in
the catchup
sub-element.
catchup
catchup
element has three optional
attributes, each a positive integer. The attributes
are threshold
, slew
,
and limit
.
frequency
frequency
attribute is an unsigned
integer specifying the frequency at
which name="tsc"
runs.
mode
mode
attribute controls how
the name="tsc"
timer is managed, and can be
"auto", "native", "emulate", "paravirt", or "smpsafe".
Other timers are always emulated.
present
present
attribute can be "yes" or "no" to
specify whether a particular timer is available to the guest.
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 devices
element.
Since 0.1.3
... <devices> <emulator>/usr/lib/xen/bin/qemu-dm</emulator> </devices> ...
emulator
emulator
element specify
the fully qualified path to the device model emulator binary.
The capabilities XML specifies
the recommended default emulator to use for each particular
domain type / architecture combination.
Any device that looks like a disk, be it a floppy, harddisk,
cdrom, or paravirtualized driver is specified via the disk
element.
... <devices> <disk type='file' snapshot='external'> <driver name="tap" type="aio" cache="default"/> <source file='/var/lib/xen/images/fv0'/ startupPolicy='optional'> <target dev='hda' bus='ide'/> <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'/> <readonly/> </disk> </devices> ...
disk
disk
element is the main container for describing
disks. The type
attribute is either "file",
"block", "dir", or "network"
and refers to the underlying source for the disk. The optional
device
attribute indicates how the disk is to be exposed
to the guest OS. Possible values for this attribute are "floppy", "disk"
and "cdrom", defaulting to "disk". The
optional snapshot
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 domain snapshot
creation. Not all snapshot modes are supported;
for example, snapshot='yes'
with a transient disk
generally does not make sense. Since 0.0.3;
"device" attribute since 0.1.4;
"network" attribute since 0.8.7; "snapshot" since
0.9.5source
type
is "file", then
the file
attribute specifies the fully-qualified
path to the file holding the disk. If the disk
type
is "block", then the dev
attribute specifies the path to the host device to serve as
the disk. If the disk type
is "network", then
the protocol
attribute specifies the protocol to
access to the requested image; possible values are "nbd",
"rbd", and "sheepdog". If the protocol
attribute
is "rbd" or "sheepdog", an additional
attribute name
is mandatory to specify which
image to be used. When the disk type
is
"network", the source
may have zero or
more host
sub-elements used to specify the hosts
to connect.
Since 0.0.3
For "file" disk type which represents cdrom or floppy
(the device
attribute) it is possible to define
policy what to do with disk if source is not accessible.
This is done by startupPolicy
attribute accepting
these values:
mandatory | fail if missing for any reason (the default) |
requisite | fail if missing on boot up, drop if missing on migrate/restore/revert |
optional | drop if missing at any start attempt |
target
target
element controls the bus / device
under which the disk is exposed to the guest
OS. The dev
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 bus
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.
Since 0.0.3; bus
attribute since 0.4.3;
"usb" attribute value since after 0.4.4; "sata" attribute value since
0.9.7driver
name
attribute selects the primary
backend driver name, while the optional type
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".
cache
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).
Since 0.6.0,
"directsync" since 0.9.5,
"unsafe" since 0.9.7
error_policy
attribute controls
how the hypervisor will behave on a disk read or write
error, possible values are "stop", "report", "ignore", and
"enospace".Since 0.8.0, "report" since
0.9.7 The default setting of error_policy is "report".
There is also an
optional rerror_policy
that controls behavior
for read errors only. Since
0.9.7. If no rerror_policy is given, error_policy
is used for both read and write errors. If rerror_policy
is given, it overrides the error_policy
for
read errors. Also note that "enospace" is not a valid
policy for read errors, so if error_policy
is
set to "enospace" and no rerror_policy
is
given, the read error policy will be left at its default,
which is "report".
io
attribute controls specific
policies on I/O; qemu guests support "threads" and
"native". Since 0.8.8
ioeventfd
attribute allows users to
set
domain I/O asynchronous handling 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.
Since 0.9.3 (QEMU and KVM only)
In general you should leave this option alone, unless you
are very certain you know what you are doing.
event_idx
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.
Since 0.9.5 (QEMU and KVM only)
In general you should leave this option alone, unless you
are very certain you know what you are doing.
boot
order
attribute determines the order in which devices will be tried during
boot sequence. The per-device boot
elements cannot be
used together with general boot elements in
BIOS bootloader section.
Since 0.8.8
encryption
readonly
type='cdrom'
.
shareable
transient
serial
<serial>WD-WMAP9A966149</serial>
.
Since 0.7.1
host
host
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.
Protocol | Meaning | Number of hosts |
---|---|---|
nbd | a server running nbd-server | only one |
rbd | monitor servers of RBD | one or more |
sheepdog | one of the sheepdog servers (default is localhost:7000) | zero or one |
address
address
element ties the disk
to a given slot of a controller (the
actual <controller>
device can often be
inferred by libvirt, although it can
be explicitly specified).
The type
attribute is mandatory, and is typically
"pci" or "drive". For a "pci" controller, additional
attributes for bus
, slot
,
and function
must be present, as well as
optional domain
and multifunction
.
Multifunction defaults to 'off'; any other value requires
QEMU 0.1.3 and libvirt 0.9.7. For a
"drive" controller, additional attributes
controller
, bus
,
and unit
are available, each defaulting to 0.
auth
auth
element provides the
authentication credentials needed to access the source. It
includes a mandatory attribute username
, which
identifies the username to use during authentication, as well
as a sub-element secret
with mandatory
attribute type
, to tie back to
a libvirt secret object 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 type
is "ceph", for Ceph RBD
network sources, and requires either an
attribute uuid
with the UUID of the Ceph secret
object, or an attribute usage
with the name
associated with the Ceph secret
object. libvirt 0.9.7
A directory on the host that can be accessed directly from the guest. since 0.3.3, since 0.8.5 for QEMU/KVM
... <devices> <filesystem type='template'> <source name='my-vm-template'/> <target dir='/'/> </filesystem> <filesystem type='mount' accessmode='passthrough'> <driver type='path'/> <source dir='/export/to/guest'/> <target dir='/import/from/host'/> <readonly/> </filesystem> ... </devices> ...
filesystem
type
specifies the type of the
source
. The possible values are:
type='mount'
type
if one is not specified.
This mode also has an optional
sub-element driver
, with an
attribute type='path'
or type='handle'
(since
0.9.7).
type='template'
type='file'
type='block'
accessmode
which specifies the security mode for accessing the source
(since 0.8.5). Currently this only works
with type='mount'
for the QEMU/KVM driver. The possible
values are:
accessmode='passthrough'
source
is accessed with the permissions of the
user inside the guest. This is the default accessmode
if
one is not specified.
More info
accessmode='mapped'
source
is accessed with the permissions of the
hypervisor (QEMU process).
More info
accessmode='squash'
source
name
attribute must be used with
type='template'
, and the dir
attribute must
be used with type='mount'
target
source
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.
readonly
readonly
attribute is available but currently
unused.
Many devices that have an <address>
sub-element are designed to work with a controller to manage
related devices. Normally, libvirt can automatically infer such
controllers without requiring explicit XML markup, but sometimes
it is necessary to provide an explicit controller element.
... <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> ...
Each controller has a mandatory attribute type
,
which must be one of "ide", "fdc", "scsi", "sata", "usb",
"ccid", or "virtio-serial", and a mandatory
attribute index
which is the decimal integer
describing in which order the bus controller is encountered (for
use in controller
attributes
of <address>
elements). The "virtio-serial"
controller has two additional optional
attributes ports
and vectors
, which
control how many devices can be connected through the
controller. A "scsi" controller has an optional
attribute model
, which is one of "auto",
"buslogic", "lsilogic", "lsias1068", or "vmpvscsi".
A "usb" controller has an optional attribute model
,
which is one of "piix3-uhci", "piix4-uhci", "ehci",
"ich9-ehci1", "ich9-uhci1", "ich9-uhci2", "ich9-uhci3",
"vt82c686b-uhci" or "pci-ohci".
For controllers that are themselves devices on a PCI or USB bus,
an optional sub-element <address>
can specify
the exact relationship of the controller to its master bus, with
semantics like any other device's address
sub-element.
USB companion controllers have an optional
sub-element <master>
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 index
value should be equal.
... <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> ...
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.
... <devices> ... <lease> <lockspace>somearea</lockspace> <key>somekey</key> <target path='/some/lease/path' offset='1024'/> </lease> ... </devices> ...
USB and PCI devices attached to the host can be passed through
to the guest using
the hostdev
element. since after
0.4.4 for USB and 0.6.0 for PCI (KVM only):
... <devices> <hostdev mode='subsystem' type='usb'> <source> <vendor id='0x1234'/> <product id='0xbeef'/> </source> <boot order='2'/> </hostdev> </devices> ...
or:
... <devices> <hostdev mode='subsystem' type='pci' managed='yes'> <source> <address bus='0x06' slot='0x02' function='0x0'/> </source> <boot order='1'/> <rom bar='off'/> </hostdev> </devices> ...
hostdev
hostdev
element is the main container for describing
host devices. For usb device passthrough mode
is always
"subsystem" and type
is "usb" for a USB device and "pci"
for a PCI device. When managed
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 managed
is omitted or "no", and for USB
devices, the user is responsible to
call virNodeDeviceDettach
(or virsh
nodedev-dettach
) before starting the guest or
hot-plugging the device,
and virNodeDeviceReAttach
(or virsh
nodedev-reattach
) after hot-unplug or stopping the
guest.source
vendor
and product
elements or by the device's
address on the hosts using the address
element.
PCI devices on the other hand can only be described by their
address
vendor
, product
vendor
and product
elements each have an
id
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.boot
order
attribute determines the order in which devices will be tried during
boot sequence. The per-device boot
elements cannot be
used together with general boot elements in
BIOS bootloader section.
Since 0.8.8rom
rom
element is used to change how a PCI
device's ROM is presented to the guest. The bar
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"). Since
0.9.7
address
address
element for USB devices has a
bus
and device
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 lspci
or
with virsh nodedev-list
. The
bus
attribute allows the hexadecimal values 0 to ff, the
slot
attribute allows the hexadecimal values 0 to 1f, and
the function
attribute allows the hexadecimal values 0 to 7.
The multifunction
attribute controls turning on the
multifunction bit for a particular slot/function in the PCI
control registersince 0.9.7, requires QEMU
0.13. multifunction
defaults to 'off', but
should be set to 'on' for function 0 of a slot that will have
multiple functions used.
There is also an optional domain
attribute for
the PCI domain, with hexadecimal values 0 to ffff, but it is
currently not used by qemu.USB device redirection through a character device is supported since after 0.9.5 (KVM only):
... <devices> <redirdev bus='usb' type='tcp'> <source mode='connect' host='localhost' service='4000'/> </redirdev> </devices> ...
redirdev
redirdev
element is the main container for
describing redirected devices. bus
must be "usb"
for a USB device.
An additional attribute type
is required,
matching one of the
supported serial device types,
to describe the host side of the
tunnel; type='tcp'
or type='spicevmc'
(which uses the usbredir
channel of a SPICE graphics
device) are typical.
The redirdev element has an optional sub-element
<address>
which can tie the device to a
particular controller.
Further sub-elements, such as <source>
, may
be required according to the given type, although
a <target>
sub-element is not required (since
the consumer of the character device is the hypervisor itself,
rather than a device visible in the guest).
A virtual smartcard device can be supplied to the guest via the
smartcard
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. Since 0.8.8
... <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> ...
The <smartcard>
element has a mandatory
attribute mode
. 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.
mode='host'
<address>
sub-element.mode='host-certificates'
certutil -d /etc/pki/nssdb -x -t
CT,CT,CT -S -s CN=cert1 -n cert1
, and the resulting three
certificate names must be supplied as the content of each of
three <certificate>
sub-elements. An
additional sub-element <database>
can specify
the absolute path to an alternate directory (matching
the -d
option of the certutil
command
when creating the certificates); if not present, it defaults to
/etc/pki/nssdb.mode='passthrough'
type
is required, matching one of the
supported serial device types, to
describe the host side of the tunnel; type='tcp'
or type='spicevmc'
(which uses the smartcard
channel of a SPICE graphics
device) are typical. Further sub-elements, such
as <source>
, may be required according to the
given type, although a <target>
sub-element
is not required (since the consumer of the character device is
the hypervisor itself, rather than a device visible in the
guest).
Each mode supports an optional
sub-element <address>
, which fine-tunes the
correlation between the smartcard and a ccid bus controller.
If present, the element must have an attribute
of type='ccid'
as well as a bus
attribute listing the index of the bus that the smartcard
utilizes. An optional slot
attribute lists which
slot within the bus. For now, qemu only supports at most one
smartcard, with an address of bus=0 slot=0.
... <devices> <interface type='bridge'> <source bridge='xenbr0'/> <mac address='00:16:3e:5d:c7:9e'/> <script path='vif-bridge'/> <boot order='1'/> </interface> </devices> ...
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 <interface>
element has an
optional <address>
sub-element that can tie
the interface to a particular pci slot, with
attribute type='pci'
and additional
attributes domain
, bus
, slot
,
function
, and multifunction
since 0.9.7, requires QEMU 0.13 as appropriate.
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 <network>
definition Since 0.9.4).
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 <forward>
element given), NAT'ing to an
explicit network device or to the default route
(<forward mode='nat'>
), routed with no NAT
(<forward mode='route'/>
), or connected
directly to one of the host's network interfaces (via macvtap)
or bridge devices ((<forward
mode='bridge|private|vepa|passthrough'/>
Since
0.9.4)
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
'virsh net-dumpxml [networkname]
'. 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 192.168.122.0/255.255.255.0
. Each guest will
have an associated tun device created with a name of vnetN,
which can also be overridden with the <target> element
(see
overriding the target element).
When the source of an interface is a network,
a portgroup
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. Since 0.9.4). Also,
similar to direct
network connections (described
below), a connection of type network
may specify
a virtportprofile
element, with configuration data
to be forwarded to a vepa or 802.1Qbh compliant switch.
... <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> ...
This is the recommended config for general guest connectivity on hosts with static wired networking configs
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 overriding the target element). 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.
... <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> ...
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 10.0.2.15
. The default router will be
10.0.2.2
and the DNS server will be 10.0.2.3
.
This networking is the only option for unprivileged users who need their
VMs to have outgoing access.
... <devices> <interface type='user'/> ... <interface type='user'> <mac address="00:11:22:33:44:55"/> </interface> </devices> ...
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.
... <devices> <interface type='ethernet'/> ... <interface type='ethernet'> <target dev='vnet7'/> <script path='/etc/qemu-ifup-mynet'/> </interface> </devices> ...
Provides direct attachment of the virtual machine's NIC to the given
physial interface of the host.
Since 0.7.7 (QEMU and KVM only)
This setup requires the Linux macvtap
driver to be available. (Since Linux 2.6.34.)
One of the modes 'vepa'
(
'Virtual Ethernet Port Aggregator'), '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:
vepa
bridge
vepa
mode,
a VEPA capable bridge is required.private
private
mode.passthrough
... <devices> <interface type='direct'/> ... <interface type='direct'> <source dev='eth0' mode='vepa'/> </interface> </devices> ...
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.
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. Since 0.8.2
Please note that IEEE 802.1Qbg requires a non-zero value for the VLAN ID.
managerid
typeid
typeidversion
instanceid
... <devices> <interface type='direct'/> ... <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> ...
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. Since 0.8.2
profileid
... <devices> <interface type='direct'/> ... <interface type='direct'> <source dev='eth0' mode='private'/> <virtualport type='802.1Qbh'> <parameters profileid='finance'/> </virtualport> </interface> </devices> ...
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.
... <devices> <interface type='mcast'> <source address='230.0.0.1' port='5558'/> </interface> </devices> ...
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.
... <devices> <interface type='server'> <source address='192.168.0.1' port='5558'/> </interface> ... <interface type='client'> <source address='192.168.0.1' port='5558'/> </interface> </devices> ...
... <devices> <interface type='network'> <source network='default'/> <target dev='vnet1'/> <model type='ne2k_pci'/> </interface> </devices> ...
For hypervisors which support this, you can set the model of emulated network interface card.
The values for type
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:
qemu -net nic,model=? /dev/null qemu-kvm -net nic,model=? /dev/null
Typical values for QEMU and KVM include: ne2k_isa i82551 i82557b i82559er ne2k_pci pcnet rtl8139 e1000 virtio
... <devices> <interface type='network'> <source network='default'/> <target dev='vnet1'/> <model type='virtio'/> <driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off'/> </interface> </devices> ...
Some NICs may have tunable driver-specific options. These are
set as attributes of the driver
sub-element of the
interface definition. Currently the following attributes are
available for the "virtio"
NIC driver:
name
name
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.
Since 0.8.8 (QEMU and KVM only)
txmode
txmode
attribute specifies how to handle
transmission of packets when the transmit buffer is full. The
value can be either 'iothread' or 'timer'.
Since 0.8.8 (QEMU and KVM only)ioeventfd
event_idx
event_idx
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.
Since 0.9.5 (QEMU and KVM only)... <devices> <interface type='network'> <source network='default'/> <target dev='vnet1'/> </interface> </devices> ...
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 must not start with either 'vnet' or 'vif', which are prefixes reserved by libvirt and certain hypervisors. Manually specified targets using these prefixes will be ignored.
... <devices> <interface type='network'> <source network='default'/> <target dev='vnet1'/> <boot order='1'/> </interface> </devices> ...
For hypervisors which support this, you can set exact NIC which should
be used for network boot. The order
attribute determines
the order in which devices will be tried during boot sequence. The
per-device boot
elements cannot be used together with
general boot elements in
BIOS bootloader section.
Since 0.8.8
... <devices> <interface type='network'> <source network='default'/> <target dev='vnet0'/> <bandwidth> <inbound average='1000' peak='5000' burst='1024'/> <outbound average='128' peak='256' burst='256'/> </bandwidth> </interface> <devices> ...
This part of interface XML provides setting quality of service. Incoming
and outgoing traffic can be shaped independently. The
bandwidth
element can have at most one inbound
and at most one outbound
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
inbound
only, and vice versa. Each of these elements have one
mandatory attribute average
. It specifies average bit rate on
interface being shaped. Then there are two optional attributes:
peak
, which specifies maximum rate at which interface can send
data, and burst
, amount of bytes that can be burst at
peak
speed. Accepted values for attributes are integer
numbers. The units for average
and peak
attributes
are kilobytes per second, and for the burst
just kilobytes.
Since 0.9.4
... <devices> <interface type='network'> <source network='default'/> <target dev='vnet0'/> <link state='down'/> </interface> <devices> ...
This element provides means of setting state of the virtual network link.
Possible values for attribute state
are up
and
down
. If down
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 up
.
Since 0.9.5
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.
... <devices> <input type='mouse' bus='usb'/> </devices> ...
input
input
element has one mandatory attribute,
the type
whose value can be either 'mouse' or
'tablet'. The latter provides absolute
cursor movement, while the former uses relative movement. The optional
bus
attribute can be used to refine the exact device type.
It takes values "xen" (paravirtualized), "ps2" and "usb".
The input
element has an optional
sub-element <address>
which can tie the
device to a particular PCI slot.
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.
... <devices> <hub type='usb'/> </devices> ...
hub
hub
element has one mandatory attribute,
the type
whose value can only be 'usb'.
The hub
element has an optional
sub-element <address>
which can tie the
device to a particular controller.
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.
... <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> ...
graphics
graphics
element has a mandatory type
attribute which takes the value "sdl", "vnc", "rdp" or "desktop":
"sdl"
display
attribute for
the display to use, an xauth
attribute for
the authentication identifier, and an
optional fullscreen
attribute accepting
values 'yes' or 'no'.
"vnc"
port
attribute
specifies the TCP port number (with -1 as legacy syntax
indicating that it should be
auto-allocated). The autoport
attribute is
the new preferred syntax for indicating autoallocation of
the TCP port to use. The listen
attribute is
an IP address for the server to listen
on. The passwd
attribute provides a VNC
password in clear text. The keymap
attribute
specifies the keymap to use. It is possible to set a limit
on the validity of the password be giving an
timestamp passwdValidTo='2010-04-09T15:51:00'
assumed to be in UTC. The connected
attribute
allows control of connected client during password changes.
VNC accepts keep
value only.
since 0.9.3
NB, this may not be supported by all hypervisors.socket
attribute for listening on a unix
domain socket path.Since 0.8.8
"spice"
Starts a SPICE server. The port
attribute
specifies the TCP port number (with -1 as legacy syntax
indicating that it should be auto-allocated),
while tlsPort
gives an alternative secure
port number. The autoport
attribute is the
new preferred syntax for indicating autoallocation of
both port numbers. The listen
attribute is
an IP address for the server to listen
on. The passwd
attribute provides a SPICE
password in clear text. The keymap
attribute specifies the keymap to use. It is possible to
set a limit on the validity of the password be giving an
timestamp passwdValidTo='2010-04-09T15:51:00'
assumed to be in UTC. The connected
attribute
allows control of connected client during password changes.
SPICE accepts keep
to keep client connected,
disconnect
to disconnect client and
fail
to fail changing password.
Since 0.9.3
NB, this may not be supported by all hypervisors.
"spice" since 0.8.6.
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 main
, display
,
inputs
, cursor
,
playback
, record
;
and since
0.8.8: smartcard
.
<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'/> </graphics>
Spice supports variable compression settings for audio,
images and streaming, since
0.9.1. These settings are accessible via
the compression
attribute in all following
elements: image
to set image compression
(accepts auto_glz
, auto_lz
,
quic
, glz
, lz
,
off
), jpeg
for JPEG
compression for images over wan
(accepts auto
, never
,
always
), zlib
for configuring
wan image compression (accepts auto
,
never
, always
)
and playback
for enabling audio stream
compression (accepts on
or off
).
Streaming mode is set by the streaming
element, settings it's mode
attribute to one
of filter
, all
or off
, since 0.9.2.
Copy & Paste functionality (via Spice agent) is set
by the clipboard
element. It is enabled by
default, and can be disabled by setting
the copypaste
property
to no
, since
0.9.3.
"rdp"
port
attribute
specifies the TCP port number (with -1 as legacy syntax
indicating that it should be
auto-allocated). The autoport
attribute is
the new preferred syntax for indicating autoallocation of
the TCP port to use. The replaceUser
attribute is a boolean deciding whether multiple
simultaneous connections to the VM are permitted.
The multiUser
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.
"desktop"
display
and fullscreen
.
Rather than putting the address information used to set up the
listening socket for graphics types vnc
and spice
in
the <graphics>
listen
attribute,
a separate subelement of <graphics>
,
called <listen>
can be specified (see the
examples above)since
0.9.4. <listen>
accepts the following
attributes:
type
address
or network
. 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).
address
type='address'
, the address
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 type='network'
.
network
type='network'
, the network
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 route
, nat
, 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.
A video device.
... <devices> <video> <model type='vga' vram='8192' heads='1'> <acceleration accel3d='yes' accel3d='yes'/> </model> </video> </devices> ...
video
video
element is the a container for describing
video devices. For backwards compatability, if no video
is set but there is a graphics
in domain xml, then libvirt
will add a default video
according to the guest type.
For a guest of type "kvm", the default video
for it is:
type
with value "cirrus", vram
with value
"9216", and heads
with value "1".
model
model
element has a mandatory type
attribute which takes the value "vga", "cirrus", "vmvga", "xen",
"vbox", or "qxl" (since 0.8.6)
depending on the hypervisor features available.
You can also provide the amount of video memory in kilobytes using
vram
and the number of screen with heads
.
acceleration
accel3d
and accel2d
attributes in the
acceleration
element.
address
address
sub-element can be used to
tie the video device to a particular PCI slot.
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.
... <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> ...
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 target
element.
The interface presented to the host is given in the type
attribute of the top-level element. The host interface is
configured by the source
element.
Each character device element has an optional
sub-element <address>
which can tie the
device to a
particular controller or PCI
slot.
A character device presents itself to the guest as one of the following types.
... <devices> <parallel type='pty'> <source path='/dev/pts/2'/> <target port='0'/> </parallel> </devices> ...
target
can have a port
attribute, which
specifies the port number. Ports are numbered starting from 0. There are
usually 0, 1 or 2 parallel ports.
... <devices> <serial type='pty'> <source path='/dev/pts/3'/> <target port='0'/> </serial> </devices> ...
target
can have a port
attribute, which
specifies the port number. Ports are numbered starting from 0. There are
usually 0, 1 or 2 serial ports.
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:
targetType
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.targetType
attribute is serial
,
then if no <serial>
element exists, the console
element will be copied to the serial element. If a <serial>
element does already exist, the console element will be ignored.targetType
attribute is not serial
,
it will be treated normally.console
element may use a targetType
of serial
. Secondary consoles must all be paravirtualized.
A virtio console device is exposed in the guest as /dev/hvc[0-7] (for more information, see http://fedoraproject.org/wiki/Features/VirtioSerial) Since 0.8.3
... <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> ...
If the console is presented as a serial port, the target
element has the same attributes as for a serial port. There is usually
only 1 console.
This represents a private communication channel between the host and the guest.
... <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='spicevmc'> <target type='virtio' name='com.redhat.spice.0'/> </channel> </devices> ...
This can be implemented in a variety of ways. The specific type of
channel is given in the type
attribute of the
target
element. Different channel types have different
target
attributes.
guestfwd
target
element must have address
and port
attributes.
Since 0.7.3virtio
name
is specified,
/dev/virtio-ports/$name (for more info, please see
http://fedoraproject.org/wiki/Features/VirtioSerial). The
optional element address
can tie the channel to a
particular type='virtio-serial'
controller.
Since 0.7.7spicevmc
main
channel. The target
element must be present, with
attribute type='virtio'
; an optional
attribute name
controls how the guest will have
access to the channel, and defaults
to name='com.redhat.spice.0'
. The
optional address
element can tie the channel to a
particular type='virtio-serial'
controller.
Since 0.8.8A character device presents itself to the host as one of the following types.
This disables all input on the character device, and sends output into the virtual machine's logfile
... <devices> <console type='stdio'> <target port='1'> </console> </devices> ...
A file is opened and all data sent to the character device is written to the file.
... <devices> <serial type="file"> <source path="/var/log/vm/vm-serial.log"/> <target port="1"/> </serial> </devices> ...
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"
... <devices> <serial type='vc'> <target port="1"/> </serial> </devices> ...
Connects the character device to the void. No data is ever provided to the input. All data written is discarded.
... <devices> <serial type='null'> <target port="1"/> </serial> </devices> ...
A Pseudo TTY is allocated using /dev/ptmx. A suitable client such as 'virsh console' can connect to interact with the serial port locally.
... <devices> <serial type="pty"> <source path="/dev/pts/3"/> <target port="1"/> </serial> </devices> ...
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.
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.
... <devices> <serial type="dev"> <source path="/dev/ttyS0"/> <target port="1"/> </serial> </devices> ...
The character device writes output to a named pipe. See pipe(7) for more info.
... <devices> <serial type="pipe"> <source path="/tmp/mypipe"/> <target port="1"/> </serial> </devices> ...
The character device acts as a TCP client connecting to a remote server.
... <devices> <serial type="tcp"> <source mode="connect" host="0.0.0.0" service="2445"/> <protocol type="raw"/> <target port="1"/> </serial> </devices> ...
Or as a TCP server waiting for a client connection.
... <devices> <serial type="tcp"> <source mode="bind" host="127.0.0.1" service="2445"/> <protocol type="raw"/> <target port="1"/> </serial> </devices> ...
Alternatively you can use telnet
instead
of raw
TCP. Since 0.8.5
you can also use telnets
(secure telnet) and tls
.
... <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> ...
The character device acts as a UDP netconsole service, sending and receiving packets. This is a lossy service.
... <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> ...
The character device acts as a UNIX domain socket server, accepting connections from local clients.
... <devices> <serial type="unix"> <source mode="bind" path="/tmp/foo"/> <target port="1"/> </serial> </devices> ...
A virtual sound card can be attached to the host via the
sound
element. Since 0.4.3
... <devices> <sound model='es1370'/> </devices> ...
sound
sound
element has one mandatory attribute,
model
, 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'
(
'ac97' only since 0.6.0, 'ich6' only since 0.8.8)
Each sound
element has an optional
sub-element <address>
which can tie the
device to a particular PCI slot.
A virtual hardware watchdog device can be added to the guest via
the watchdog
element.
Since 0.7.3, QEMU and KVM only
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.
Currently libvirt does not support notification when the watchdog fires. This feature is planned for a future version of libvirt.
... <devices> <watchdog model='i6300esb'/> </devices> ...
... <devices> <watchdog model='i6300esb' action='poweroff'/> </devices> </domain>
model
The required model
attribute specifies what real
watchdog device is emulated. Valid values are specific to the
underlying hypervisor.
QEMU and KVM support:
action
The optional action
attribute describes what
action to take when the watchdog expires. Valid values are
specific to the underlying hypervisor.
QEMU and KVM support:
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.
Note 2: the directory to save dump files can be configured
by auto_dump_path
in file /etc/libvirt/qemu.conf.
A virtual memory balloon device is added to all Xen and KVM/QEMU
guests. It will be seen as memballoon
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.
Since 0.8.3, Xen, QEMU and KVM only
Additionally, since 0.8.4, if the
memballoon device needs to be explicitly disabled,
model='none'
may be used.
Example automatically added device with KVM
... <devices> <memballoon model='virtio'/> </devices> ...
Example manually added device with static PCI slot 2 requested
... <devices> <watchdog model='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> </devices> </domain>
model
The required model
attribute specifies what type
of balloon device is provided. Valid values are specific to
the virtualization platform
The seclabel
element allows control over the
operation of the security drivers. There are two basic
modes of operation, dynamic where libvirt automatically
generates a unique security label, or static where the
application/administrator chooses the labels. 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
Valid input XML configurations for the security label are:
<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>
When viewing the XML for a running guest with automatic
resource relabeling active, an additional XML element,
imagelabel
, will be included. This is an
output-only element, so will be ignored in user supplied
XML documents
type
static
or dynamic
to determine
whether libvirt automatically generates a unique security label
or not.
model
relabel
yes
or no
. This must always
be yes
if dynamic label assignment is used. With
static label assignment it will default to no
.
label
baselabel
imagelabel
Example configurations for each driver are provide on the driver specific pages listed below