# Domain XML format

- Element and attribute overview
  - General metadata
  - Operating system booting
    - BIOS bootloader
    - Host bootloader
    - Direct kernel boot
  - SMBIOS System Information
  - CPU Allocation
  - CPU Tuning
  - Memory Allocation
  - Memory Backing
  - Memory Tuning
  - NUMA Node Tuning
  - Block I/O Tuning
  - CPU model and topology
  - Lifecycle control
  - Hypervisor features
  - Time keeping
  - Devices
    - Hard drives, floppy disks, CDROMs
    - Filesystems
    - Controllers
    - Device leases
    - USB and PCI devices
    - Redirected devices
    - Smartcard devices
    - Network interfaces
      - Virtual network
      - Bridge to LAN
      - Userspace SLIRP stack
      - Generic ethernet connection
      - Direct attachment to physical interface
      - Multicast tunnel
      - TCP tunnel
      - Setting the NIC model
      - Setting NIC driver-specific options
      - Overriding the target element
      - Specifying boot order
      - Quality of service
      - Modyfing virtual link state
    - Input devices
    - Hub devices
    - Graphical framebuffers
    - Video devices
    - Consoles, serial, parallel & channel devices
      - Guest interface
        - Parallel port
        - Serial port
        - Console
        - Channel
      - Host interface
        - Domain logfile
        - Device logfile
        - Virtual console
        - Null device
        - Pseudo TTY
        - Host device proxy
        - Named pipe
        - TCP client/server
        - UDP network console
        - UNIX domain socket client/server
    - Sound devices
    - Watchdog device
    - Memory balloon device
  - Security label
- Example configs

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

## Element and attribute overview

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.

### General metadata

    <domain type='xen' id='3'>
      <name>fv0</name>
      <uuid>4dea22b31d52d8f32516782e98ab3fa0</uuid>
      <description>Some human readable description</description>
      ...

`name`
  The content of the `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 0.0.1
`uuid`
  The content of the `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 0.8.7
`description`
  The content of the `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 0.7.2

### Operating system booting

There are a number of different ways to boot virtual machines each with their own pros and cons.

#### BIOS bootloader

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`
  The content of the `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 0.0.1
`loader`
  The optional `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 0.1.0
`boot`
  The `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`
  Whether or not to enable an interactive boot menu prompt on guest startup. The `enable` attribute can be either "yes" or "no". If not specified, the hypervisor default is used. Since 0.8.3
`smbios`
  How to populate SMBIOS information visible in the guest. The `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`
  This element has attribute `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

#### Host bootloader

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`
  The content of the `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 0.1.0
`bootloader_args`
  The optional `bootloader_args` element allows command line arguments to be passed to the bootloader. Since 0.2.3

#### Direct kernel boot

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`
  This element has the same semantics as described earlier in the BIOS boot section
`loader`
  This element has the same semantics as described earlier in the BIOS boot section
`kernel`
  The contents of this element specify the fully-qualified path to the kernel image in the host OS.
`initrd`
  The contents of this element specify the fully-qualified path to the (optional) ramdisk image in the host OS.
`cmdline`
  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

### SMBIOS System Information

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`
  Sub-elements call out specific SMBIOS values, which will affect the guest if used in conjunction with the `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`
    This is block 0 of SMBIOS, with entry names drawn from "vendor", "version", "date", and "release".
  `system`
    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 `uuid` element, the two values must match.

### CPU Allocation

    <domain>
      ...
      <vcpu cpuset="1-4,^3,6" current="1">2</vcpu>
      ...
    </domain>

`vcpu`
  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. Since 0.4.4, this element can contain an optional `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.

### CPU Tuning

    <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`
  The optional `cputune` element provides details regarding the cpu tunable parameters for the domain. Since 0.9.0
`vcpupin`
  The optional `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`
  The optional `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`
  The optional `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`
  The optional `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

### Memory Allocation

    <domain>
      ...
      <memory>524288</memory>
      <currentMemory>524288</currentMemory>
      ...
    </domain>

`memory`
  The maximum allocation of memory for the guest at boot time. The units for this value are kilobytes (i.e. blocks of 1024 bytes)
`currentMemory`
  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 `memory` element

### Memory Backing

    <domain>
      ...
      <memoryBacking>
        <hugepages/>
      </memoryBacking>
      ...
    </domain>

`memoryBacking`
  The optional `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.

### Memory Tuning

    <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`
  The optional `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`
  The optional `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`
  The optional `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`
  The optional `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 provided
`min_guarantee`
  The optional `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)

### NUMA Node Tuning

    <domain>
      ...
      <numatune>
        <memory mode="strict" nodeset="1-4,^3"/>
      </numatune>
      ...
    </domain>

`numatune`
  The optional `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`
  The optional `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

### Block I/O Tuning

    <domain>
      ...
      <blkiotune>
        <weight>800</weight>
      </blkiotune>
      ...
    </domain>

`blkiotune`
  The optional `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`
  The optional `weight` element is the I/O weight of the guest. The value should be in range [100, 1000].

### CPU model and topology

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`
  The `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`
    The specified CPU model and features describes the minimum requested CPU.
  `exact`
    The virtual CPU provided to the guest will exactly match the specification
  `strict`
    The guest will not be created unless the host CPU does exactly match the specification.
  Since 0.8.5 the `match` attribute can be omitted and will default to `exact`.
`model`
  The content of the `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`
  Since 0.8.3 the content of the `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`
  The `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`
  The `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`
    The virtual CPU will claim the feature is supported regardless of it being supported by host CPU.
  `require`
    Guest creation will fail unless the feature is supported by host CPU.
  `optional`
    The feature will be supported by virtual CPU if and only if it is supported by host CPU.
  `disable`
    The feature will not be supported by virtual CPU.
  `forbid`
    Guest creation will fail if the feature is supported by host CPU.
  Since 0.8.5 the `policy` attribute can be omitted and will default to `require`.

### Lifecycle control

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`
  The content of this element specifies the action to take when the guest requests a poweroff.
`on_reboot`
  The content of this element specifies the action to take when the guest requests a reboot.
`on_crash`
  The content of this element specifies the action to take when the guest crashes.

Each of these states allow for the same four possible actions.

`destroy`
  The domain will be terminated completely and all resources released
`restart`
  The domain will be terminated, and then restarted with the same configuration
`preserve`
  The domain will be terminated, and its resource preserved to allow analysis.
`rename-restart`
  The domain will be terminated, and then restarted with a new name

on_crash supports these additional actions since 0.8.4.

`coredump-destroy`
  The crashed domain's core will be dumped, and then the domain will be terminated completely and all resources released
`coredump-restart`
  The crashed domain's core will be dumped, and then the domain will be restarted with the same configuration

### Hypervisor features

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`
  Physical address extension mode allows 32-bit guests to address more than 4 GB of memory.
`acpi`
  ACPI is useful for power management, for example, with KVM guests it is required for graceful shutdown to work.
`hap`
  Enable use of Hardware Assisted Paging if available in the hardware.

### Time keeping

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`
    The guest clock will always be synchronized to UTC when booted
  `localtime`
    The guest clock will be synchronized to the host's configured timezone when booted, if any.
  `timezone`
    The guest clock will be synchronized to the requested timezone using the `timezone` attribute. Since 0.7.7
  `variable`
    The guest clock will have an arbitrary offset applied relative to UTC. The delta relative to UTC is specified in seconds, using the `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`
    The `name` attribute selects which timer is being modified, and can be one of "platform", "pit", "rtc", "hpet", or "tsc".
  `track`
    The `track` attribute specifies what the timer tracks, and can be "boot", "guest", or "wall". Only valid for `name="rtc"` or `name="platform"`.
  `tickpolicy`
    The `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`
      The `catchup` element has three optional attributes, each a positive integer. The attributes are `threshold`, `slew`, and `limit`.
  `frequency`
    The `frequency` attribute is an unsigned integer specifying the frequency at which `name="tsc"` runs.
  `mode`
    The `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`
    The `present` attribute can be "yes" or "no" to specify whether a particular timer is available to the guest.

### Devices

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`
  The contents of the `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.

#### Hard drives, floppy disks, CDROMs

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`
  The `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 0.9.5
`source`
  If the disk `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

  Since 0.9.7
`target`
  The `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 0.9.7
`driver`
  The optional driver element allows specifying further details related to the hypervisor driver used to provide the disk. Since 0.1.8
  - If the hypervisor supports multiple backend drivers, then the `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".
  - The optional `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
  - The optional `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".
  - The optional `io` attribute controls specific policies on I/O; qemu guests support "threads" and "native". Since 0.8.8
  - The optional `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.
  - The optional `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`
  Specifies that the disk is bootable. 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
`encryption`
  If present, specifies how the volume is encrypted. See the Storage Encryption page for more information.
`readonly`
  If present, this indicates the device cannot be modified by the guest. For now, this is the default for disks with attribute `type='cdrom'`.
`shareable`
  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.
`transient`
  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. Since 0.9.5
`serial`
  If present, this specify serial number of virtual hard drive. For example, it may look like `<serial>WD-WMAP9A966149</serial>`. Since 0.7.1
`host`
  The `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`
  If present, the `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`
  If present, the `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

#### Filesystems

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`
  The filesystem attribute `type` specifies the type of the `source`. The possible values are:
  `type='mount'`
    A host directory to mount in the guest. Used by LXC, OpenVZ (since 0.6.2) and QEMU/KVM (since 0.8.5). This is the default `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'`
    OpenVZ filesystem template. Only used by OpenVZ driver.
  `type='file'`
    Currently unused.
  `type='block'`
    A host block device to mount in the guest. The filesystem format will be autodetected. Only used by LXC driver (since 0.9.5).
  The filesystem block has an optional attribute `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'`
    The `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'`
    The `source` is accessed with the permissions of the hypervisor (QEMU process). More info
  `accessmode='squash'`
    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. More info
`source`
  The resource on the host that is being accessed in the guest. The `name` attribute must be used with `type='template'`, and the `dir` attribute must be used with `type='mount'`
`target`
  Where the `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`
  An optional `readonly` attribute is available but currently unused.

#### Controllers

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>
      ...

#### Device leases

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>
      ...

lockspace
  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.
key
  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.
target
  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.

#### USB and PCI 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`
  The `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`
  The source element describes the device as seen from the host. The USB device can either be addressed by vendor / product id using the `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`
  The `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`
  Specifies that the device is bootable. 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
`rom`
  The `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`
  The `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.

#### Redirected devices

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`
  The `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).

#### Smartcard devices

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'`
  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 `<address>` sub-element.
`mode='host-certificates'`
  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 `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'`
  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 `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.

#### Network interfaces

      ...
      <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.

##### Virtual network

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>
      ...

##### Bridge to LAN

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>
      ...

##### Userspace SLIRP stack

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>
      ...

##### Generic ethernet connection

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>
      ...

##### Direct attachment to physical interface

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`
  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).
`bridge`
  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 `vepa` mode, a VEPA capable bridge is required.
`private`
  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 `private` mode.
`passthrough`
  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. Since 0.9.2

      ...
      <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`
  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.
`typeid`
  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.
`typeidversion`
  The VSI Type Version allows multiple versions of a VSI Type. This is an integer value.
`instanceid`
  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.

      ...
      <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`
  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.

      ...
      <devices>
        <interface type='direct'/>
        ...
        <interface type='direct'>
          <source dev='eth0' mode='private'/>
          <virtualport type='802.1Qbh'>
            <parameters profileid='finance'/>
          </virtualport>
        </interface>
      </devices>
      ...

##### Multicast tunnel

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>
      ...

##### TCP tunnel

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>
      ...

##### Setting the NIC model

      ...
      <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

##### Setting NIC driver-specific options

      ...
      <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`
  The optional `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`
  The `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)
  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).
  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.
  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."
  In general you should leave this option alone, unless you are very certain you know what you are doing.
`ioeventfd`
  This optional attribute allows users to set domain I/O asynchronous handling 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. 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`
  The `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.

##### Overriding the target element

      ...
      <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.

##### Specifying boot order

      ...
      <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

##### Quality of service

      ...
      <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

##### Modyfing virtual link state

      ...
      <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

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`
  The `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.

#### Hub devices

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`
  The `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.

#### Graphical framebuffers

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`
  The `graphics` element has a mandatory `type` attribute which takes the value "sdl", "vnc", "rdp" or "desktop":
  `"sdl"`
    This displays a window on the host desktop, it can take 3 optional arguments: a `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"`
    Starts a VNC server. The `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.
    Rather than using listen/port, QEMU supports a `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"`
    Starts a RDP server. The `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"`
    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 `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`
  Set to either `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`
  if `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`
  if `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.

#### Video devices

A video device.

      ...
      <devices>
        <video>
          <model type='vga' vram='8192' heads='1'>
            <acceleration accel3d='yes' accel3d='yes'/>
          </model>
        </video>
      </devices>
      ...

`video`
  The `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`
  The `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`
  If acceleration should be enabled (if supported) using the `accel3d` and `accel2d` attributes in the `acceleration` element.
`address`
  The optional `address` sub-element can be used to tie the video device to a particular PCI slot.

#### Consoles, serial, parallel & channel devices

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.

##### Guest interface

A character device presents itself to the guest as one of the following types.

###### Parallel port

      ...
      <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.

###### Serial port

      ...
      <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.

###### Console

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:

- If no `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.
- If the `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.
- If the `targetType` attribute is not `serial`, it will be treated normally.
- Only the first `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.

###### Channel

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`
  TCP traffic sent by the guest to a given IP address and port is forwarded to the channel device on the host. The `target` element must have `address` and `port` attributes. Since 0.7.3
`virtio`
  Paravirtualized virtio channel. Channel is exposed in the guest under /dev/vport*, and if the optional element `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 0.7.7
`spicevmc`
  Paravirtualized SPICE channel. The domain must also have a SPICE server as a graphics device, at which point the host piggy-backs messages across the `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 0.8.8

##### Host interface

A character device presents itself to the host as one of the following types.

###### Domain logfile

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>
      ...

###### Device logfile

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>
      ...

###### Virtual console

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>
      ...

###### Null device

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>
      ...

###### Pseudo TTY

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.

###### Host device proxy

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>
      ...

###### Named pipe

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>
      ...

###### TCP client/server

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>
      ...

###### UDP network console

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>
      ...

###### UNIX domain socket client/server

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>
      ...

#### Sound 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`
  The `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.

#### Watchdog device

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:

  - 'i6300esb' — the recommended device, emulating a PCI Intel 6300ESB
  - 'ib700' — emulating an ISA iBase IB700
`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:

  - 'reset' — default, forcefully reset the guest
  - 'shutdown' — gracefully shutdown the guest (not recommended)
  - 'poweroff' — forcefully power off the guest
  - 'pause' — pause the guest
  - 'none' — do nothing
  - 'dump' — automatically dump the guest Since 0.8.7

  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.

#### Memory balloon device

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

  - 'virtio' — default with QEMU/KVM
  - 'xen' — default with Xen

### Security label

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`
  Either `static` or `dynamic` to determine whether libvirt automatically generates a unique security label or not.
`model`
  A valid security model name, matching the currently activated security model
`relabel`
  Either `yes` or `no`. This must always be `yes` if dynamic label assignment is used. With static label assignment it will default to `no`.
`label`
  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
`baselabel`
  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
`imagelabel`
  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

## Example configs

Example configurations for each driver are provide on the driver specific pages listed below

- Xen examples
- QEMU/KVM examples