A short description - title

.. role:: since .. role:: anchor(raw) :format: html ================= Domain XML format ================= .. contents:: 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 `__ :anchor:`` 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" and "lxc". The second attribute is ``id`` which is a unique integer identifier for the running guest machine. Inactive machines have no id value. :anchor:`` General metadata ---------------- :: MyGuest 4dea22b3-1d52-d8f3-2516-782e98ab3fa0 43dc0cf8-809b-4adb-9bea-a9abb5f3d90e A short description - title - of the domain Some human readable description .. .. ... ``name`` The content of the ``name`` element provides a short name for the virtual machine. This name should consist only of alphanumeric 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:`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 <#elementsSysinfo>`__ specification. :since:`Since 0.0.1, sysinfo since 0.8.7` ``genid`` :since:`Since 4.4.0` , the ``genid`` element can be used to add a Virtual Machine Generation ID which exposes a 128-bit, cryptographically random, integer value identifier, referred to as a Globally Unique Identifier (GUID) using the same format as the ``uuid``. The value is used to help notify the guest operating system when the virtual machine is re-executing something that has already executed before, such as: - VM starts executing a snapshot - VM is recovered from backup - VM is failover in a disaster recovery environment - VM is imported, copied, or cloned The guest operating system notices the change and is then able to react as appropriate by marking its copies of distributed databases as dirty, re-initializing its random number generator, etc. The libvirt XML parser will accept both a provided GUID value or just in which case a GUID will be generated and saved in the XML. For the transitions such as above, libvirt will change the GUID before re-executing. ``title`` The optional element ``title`` provides space for a short description of the domain. The title should not contain any newlines. :since:`Since 0.9.10` . ``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:`Since 0.7.2` ``metadata`` The ``metadata`` node can be used by applications to store custom metadata in the form of XML nodes/trees. Applications must use custom namespaces on their XML nodes/trees, with only one top-level element per namespace (if the application needs structure, they should have sub-elements to their namespace element). :since:`Since 0.9.10` :anchor:`` Operating system booting ------------------------ There are a number of different ways to boot virtual machines each with their own pros and cons. :anchor:`` 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. :: ... hvm /usr/lib/xen/boot/hvmloader /var/lib/libvirt/nvram/guest_VARS.fd ... ``firmware`` The ``firmware`` attribute allows management applications to automatically fill ```` and ```` elements and possibly enable some features required by selected firmware. Accepted values are ``bios`` and ``efi``. The selection process scans for files describing installed firmware images in specified location and uses the most specific one which fulfils domain requirements. The locations in order of preference (from generic to most specific one) are: - ``/usr/share/qemu/firmware`` - ``/etc/qemu/firmware`` - ``$XDG_CONFIG_HOME/qemu/firmware`` For more information refer to firmware metadata specification as described in ``docs/interop/firmware.json`` in QEMU repository. Regular users do not need to bother. :since:`Since 5.2.0 (QEMU and KVM only)` For VMware guests, this is set to ``efi`` when the guest uses UEFI, and it is not set when using BIOS. :since:`Since 5.3.0 (VMware ESX and Workstation/Player)` ``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. If ``arch`` is omitted then for most hypervisor drivers, the host native arch will be chosen. For the ``test``, ``ESX`` and ``VMWare`` hypervisor drivers, however, the ``i686`` arch will always be chosen even on an ``x86_64`` host. :since:`Since 0.0.1` ``firmware`` :since:`Since 7.2.0 QEMU/KVM only` When using firmware auto-selection there are different features enabled in the firmwares. The list of features can be used to limit what firmware should be automatically selected for the VM. The list of features can be specified using zero or more ``feature`` elements. Libvirt will take into consideration only the listed features and ignore the rest when selecting the firmware. ``feature`` The list of mandatory attributes: - ``enabled`` (accepted values are ``yes`` and ``no``) is used to tell libvirt if the feature must be enabled or not in the automatically selected firmware - ``name`` the name of the feature, the list of the features: - ``enrolled-keys`` whether the selected nvram template has default certificate enrolled. Firmware with Secure Boot feature but without enrolled keys will successfully boot non-signed binaries as well. Valid only for firmwares with Secure Boot feature. - ``secure-boot`` whether the firmware implements UEFI Secure boot feature. ``loader`` The optional ``loader`` tag refers to a firmware blob, which is specified by absolute path, used to assist the domain creation process. It is used by Xen fully virtualized domains as well as setting the QEMU BIOS file path for QEMU/KVM domains. :since:`Xen since 0.1.0, QEMU/KVM since 0.9.12` Then, :since:`since 1.2.8` it's possible for the element to have two optional attributes: ``readonly`` (accepted values are ``yes`` and ``no``) to reflect the fact that the image should be writable or read-only. The second attribute ``type`` accepts values ``rom`` and ``pflash``. It tells the hypervisor where in the guest memory the file should be mapped. For instance, if the loader path points to an UEFI image, ``type`` should be ``pflash``. Moreover, some firmwares may implement the Secure boot feature. Attribute ``secure`` can be used to tell the hypervisor that the firmware is capable of Secure Boot feature. It cannot be used to enable or disable the feature itself in the firmware. :since:`Since 2.1.0` ``nvram`` Some UEFI firmwares may want to use a non-volatile memory to store some variables. In the host, this is represented as a file and the absolute path to the file is stored in this element. Moreover, when the domain is started up libvirt copies so called master NVRAM store file defined in ``qemu.conf``. If needed, the ``template`` attribute can be used to per domain override map of master NVRAM stores from the config file. Note, that for transient domains if the NVRAM file has been created by libvirt it is left behind and it is management application's responsibility to save and remove file (if needed to be persistent). :since:`Since 1.2.8` ``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. Multiple devices of the same type are sorted according to their targets while preserving the order of buses. After defining the domain, its XML configuration returned by libvirt (through virDomainGetXMLDesc) lists devices in the sorted order. Once sorted, the first device is marked as bootable. Thus, e.g., a domain configured to boot from "hd" with vdb, hda, vda, and hdc disks assigned to it will boot from vda (the sorted list is vda, vdb, hda, hdc). Similar domain with hdc, vda, vdb, and hda disks will boot from hda (sorted disks are: hda, hdc, vda, vdb). It can be tricky to configure in the desired way, which is why per-device boot elements (see `disks <#elementsDisks>`__, `network interfaces <#elementsNICS>`__, and `USB and PCI devices <#elementsHostDev>`__ sections below) were introduced and they are the preferred way providing full control over booting order. The ``boot`` element and per-device boot elements are mutually exclusive. :since:`Since 0.1.3, per-device boot since 0.8.8` ``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 <#elementsSysinfo>`__ element). If not specified, the hypervisor default is used. :since:`Since 0.8.7` Up till here the BIOS/UEFI configuration knobs are generic enough to be implemented by majority (if not all) firmwares out there. However, from now on not every single setting makes sense to all firmwares. For instance, ``rebootTimeout`` doesn't make sense for UEFI, ``useserial`` might not be usable with a BIOS firmware that doesn't produce any output onto serial line, etc. Moreover, firmwares don't usually export their capabilities for libvirt (or users) to check. And the set of their capabilities can change with every new release. Hence users are advised to try the settings they use before relying on them in production. ``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:`Since 0.8.3` Additional attribute ``timeout`` takes the number of milliseconds the boot menu should wait until it times out. Allowed values are numbers in range [0, 65535] inclusive and it is ignored unless ``enable`` is set to "yes". :since:`Since 1.2.8` ``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 <#elementCharSerial>`__ defined. :since:`Since 0.9.4` . :since:`Since 0.10.2 (QEMU only)` there is another attribute, ``rebootTimeout`` that controls whether and after how long the guest should start booting again in case the boot fails (according to BIOS). The value is in milliseconds with maximum of ``65535`` and special value ``-1`` disables the reboot. :anchor:`` 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. The Bhyve hypervisor also uses a host bootloader, either ``bhyveload`` or ``grub-bhyve``. :: ... /usr/bin/pygrub --append single ... ``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:`Since 0.1.0` ``bootloader_args`` The optional ``bootloader_args`` element allows command line arguments to be passed to the bootloader. :since:`Since 0.2.3` :anchor:`` 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. :: ... hvm /usr/lib/xen/boot/hvmloader /root/f8-i386-vmlinuz /root/f8-i386-initrd console=ttyS0 ks=http://example.com/f8-i386/os/ /root/ppc.dtb /path/to/slic.dat

... ``pm`` These elements enable ('yes') or disable ('no') BIOS support for S3 (suspend-to-mem) and S4 (suspend-to-disk) ACPI sleep states. If nothing is specified, then the hypervisor will be left with its default value. Note: This setting cannot prevent the guest OS from performing a suspend as the guest OS itself can choose to circumvent the unavailability of the sleep states (e.g. S4 by turning off completely). :anchor:`` Hypervisor features ------------------- Hypervisors may allow certain CPU / machine features to be toggled on/off. :: ...

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somevalue

`` sub-element to describe where the device is placed on the virtual bus presented to the guest. If an address (or any optional attribute within an address) is omitted on input, libvirt will generate an appropriate address; but an explicit address is required if more control over layout is required. See below for device examples including an address element. Every address has a mandatory attribute ``type`` that describes which bus the device is on. The choice of which address to use for a given device is constrained in part by the device and the architecture of the guest. For example, a ```` device uses ``type='drive'``, while a ```` device would use ``type='pci'`` on i686 or x86_64 guests, or ``type='spapr-vio'`` on PowerPC64 pseries guests. Each address type has further optional attributes that control where on the bus the device will be placed: ``pci`` PCI addresses have the following additional attributes: ``domain`` (a 2-byte hex integer, not currently used by qemu), ``bus`` (a hex value between 0 and 0xff, inclusive), ``slot`` (a hex value between 0x0 and 0x1f, inclusive), and ``function`` (a value between 0 and 7, inclusive). Also available is the ``multifunction`` attribute, which controls turning on the multifunction bit for a particular slot/function in the PCI control register ( :since:`since 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. ( :since:`Since 4.10.0` ), PCI address extensions depending on the architecture are supported. For example, PCI addresses for S390 guests will have a ``zpci`` child element, with two attributes: ``uid`` (a hex value between 0x0001 and 0xffff, inclusive), and ``fid`` (a hex value between 0x00000000 and 0xffffffff, inclusive) used by PCI devices on S390 for User-defined Identifiers and Function Identifiers. :since:`Since 1.3.5` , some hypervisor drivers may accept an ``

`` element with no other attributes as an explicit request to assign a PCI address for the device rather than some other type of address that may also be appropriate for that same device (e.g. virtio-mmio). The relationship between the PCI addresses configured in the domain XML and those seen by the guest OS can sometime seem confusing: a separate document describes `how PCI addresses work `__ in more detail. ``drive`` Drive addresses have the following additional attributes: ``controller`` (a 2-digit controller number), ``bus`` (a 2-digit bus number), ``target`` (a 2-digit target number), and ``unit`` (a 2-digit unit number on the bus). ``virtio-serial`` Each virtio-serial address has the following additional attributes: ``controller`` (a 2-digit controller number), ``bus`` (a 2-digit bus number), and ``slot`` (a 2-digit slot within the bus). ``ccid`` A CCID address, for smart-cards, has the following additional attributes: ``bus`` (a 2-digit bus number), and ``slot`` attribute (a 2-digit slot within the bus). :since:`Since 0.8.8.` ``usb`` USB addresses have the following additional attributes: ``bus`` (a hex value between 0 and 0xfff, inclusive), and ``port`` (a dotted notation of up to four octets, such as 1.2 or 2.1.3.1). ``spapr-vio`` On PowerPC pseries guests, devices can be assigned to the SPAPR-VIO bus. It has a flat 32-bit address space; by convention, devices are generally assigned at a non-zero multiple of 0x00001000, but other addresses are valid and permitted by libvirt. Each address has the following additional attribute: ``reg`` (the hex value address of the starting register). :since:`Since 0.9.9.` ``ccw`` S390 guests with a ``machine`` value of s390-ccw-virtio use the native CCW bus for I/O devices. CCW bus addresses have the following additional attributes: ``cssid`` (a hex value between 0 and 0xfe, inclusive), ``ssid`` (a value between 0 and 3, inclusive) and ``devno`` (a hex value between 0 and 0xffff, inclusive). Partially specified bus addresses are not allowed. If omitted, libvirt will assign a free bus address with cssid=0xfe and ssid=0. Virtio-ccw devices must have their cssid set to 0xfe. :since:`Since 1.0.4` ``virtio-mmio`` This places the device on the virtio-mmio transport, which is currently only available for some ``armv7l`` and ``aarch64`` virtual machines. virtio-mmio addresses do not have any additional attributes. :since:`Since 1.1.3` If the guest architecture is ``aarch64`` and the machine type is ``virt``, libvirt will automatically assign PCI addresses to devices; however, the presence of a single device with virtio-mmio address in the guest configuration will cause libvirt to assign virtio-mmio addresses to all further devices. :since:`Since 3.0.0` ``isa`` ISA addresses have the following additional attributes: ``iobase`` and ``irq``. :since:`Since 1.2.1` ``unassigned`` For PCI hostdevs, ``

`` allows the admin to include a PCI hostdev in the domain XML definition, without making it available for the guest. This allows for configurations in which Libvirt manages the device as a regular PCI hostdev, regardless of whether the guest will have access to it. ``

`` is an invalid address type for all other device types. :since:`Since 6.0.0` :anchor:`` Virtio-related options ~~~~~~~~~~~~~~~~~~~~~~ QEMU's virtio devices have some attributes related to the virtio transport under the ``driver`` element: The ``iommu`` attribute enables the use of emulated IOMMU by the device. The attribute ``ats`` controls the Address Translation Service support for PCIe devices. This is needed to make use of IOTLB support (see `IOMMU device <#elementsIommu>`__). Possible values are ``on`` or ``off``. :since:`Since 3.5.0` The attribute ``packed`` controls if QEMU should try to use packed virtqueues. Compared to regular split queues, packed queues consist of only a single descriptor ring replacing available and used ring, index and descriptor buffer. This can result in better cache utilization and performance. If packed virtqueues are actually used depends on the feature negotiation between QEMU, vhost backends and guest drivers. Possible values are ``on`` or ``off``. :since:`Since 6.3.0 (QEMU and KVM only)` :anchor:`` Virtio transitional devices ~~~~~~~~~~~~~~~~~~~~~~~~~~~ :since:`Since 5.2.0` , some of QEMU's virtio devices, when used with PCI/PCIe machine types, accept the following ``model`` values: ``virtio-transitional`` This device can work both with virtio 0.9 and virtio 1.0 guest drivers, so it's the best choice when compatibility with older guest operating systems is desired. libvirt will plug the device into a conventional PCI slot. ``virtio-non-transitional`` This device can only work with virtio 1.0 guest drivers, and it's the recommended option unless compatibility with older guest operating systems is necessary. libvirt will plug the device into either a PCI Express slot or a conventional PCI slot based on the machine type, resulting in a more optimized PCI topology. ``virtio`` This device will work like a ``virtio-non-transitional`` device when plugged into a PCI Express slot, and like a ``virtio-transitional`` device otherwise; libvirt will pick one or the other based on the machine type. This is the best choice when compatibility with libvirt versions older than 5.2.0 is necessary, but it's otherwise not recommended to use it. While the information outlined above applies to most virtio devices, there are a few exceptions: - for SCSI controllers, there is no ``virtio`` model available due to historical reasons: use ``virtio-scsi`` instead, which behaves the same as ``virtio`` does for other devices. Both ``virtio-transitional`` and ``virtio-non-transitional`` work with SCSI controllers; - some devices, such as GPUs and input devices (keyboard, tablet and mouse), are only defined in the virtio 1.0 spec and as such don't have a transitional variant: the only accepted model is ``virtio``, which will result in a non-transitional device. For more details see the `qemu patch posting `__ and the `virtio-1.0 spec `__. :anchor:`` Controllers ~~~~~~~~~~~ Depending on the guest architecture, some device buses can appear more than once, with a group of virtual devices tied to a virtual controller. Normally, libvirt can automatically infer such controllers without requiring explicit XML markup, but sometimes it is necessary to provide an explicit controller element, notably when planning the `PCI topology `__ for guests where device hotplug is expected. :: ...

... ... Each controller has a mandatory attribute ``type``, which must be one of 'ide', 'fdc', 'scsi', 'sata', 'usb', 'ccid', 'virtio-serial' or 'pci', 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 ``

`` elements). :since:`Since 1.3.5` the index is optional; if not specified, it will be auto-assigned to be the lowest unused index for the given controller type. Some controller types have additional attributes that control specific features, such as: ``virtio-serial`` The ``virtio-serial`` controller has two additional optional attributes ``ports`` and ``vectors``, which control how many devices can be connected through the controller. :since:`Since 5.2.0` , it supports an optional attribute ``model`` which can be 'virtio', 'virtio-transitional', or 'virtio-non-transitional'. See `Virtio transitional devices <#elementsVirtioTransitional>`__ for more details. ``scsi`` A ``scsi`` controller has an optional attribute ``model``, which is one of 'auto', 'buslogic', 'ibmvscsi', 'lsilogic', 'lsisas1068', 'lsisas1078', 'virtio-scsi', 'vmpvscsi', 'virtio-transitional', 'virtio-non-transitional', 'ncr53c90' (as builtin implicit controller only), 'am53c974', 'dc390'. See `Virtio transitional devices <#elementsVirtioTransitional>`__ for more details. ``usb`` 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", "pci-ohci", "nec-xhci", "qusb1" (xen pvusb with qemu backend, version 1.1), "qusb2" (xen pvusb with qemu backend, version 2.0) or "qemu-xhci". Additionally, :since:`since 0.10.0` , if the USB bus needs to be explicitly disabled for the guest, ``model='none'`` may be used. :since:`Since 1.0.5` , no default USB controller will be built on s390. :since:`Since 1.3.5` , USB controllers accept a ``ports`` attribute to configure how many devices can be connected to the controller. ``ide`` :since:`Since 3.10.0` for the vbox driver, the ``ide`` controller has an optional attribute ``model``, which is one of "piix3", "piix4" or "ich6". ``xenbus`` :since:`Since 5.2.0` , the ``xenbus`` controller has an optional attribute ``maxGrantFrames``, which specifies the maximum number of grant frames the controller makes available for connected devices. :since:`Since 6.3.0` , the xenbus controller supports the optional ``maxEventChannels`` attribute, which specifies maximum number of event channels (PV interrupts) that can be used by the guest. Note: The PowerPC64 "spapr-vio" addresses do not have an associated controller. For controllers that are themselves devices on a PCI or USB bus, an optional sub-element ``

`` can specify the exact relationship of the controller to its master bus, with semantics `given above <#elementsAddress>`__. An optional sub-element ``driver`` can specify the driver specific options: ``queues`` The optional ``queues`` attribute specifies the number of queues for the controller. For best performance, it's recommended to specify a value matching the number of vCPUs. :since:`Since 1.0.5 (QEMU and KVM only)` ``cmd_per_lun`` The optional ``cmd_per_lun`` attribute specifies the maximum number of commands that can be queued on devices controlled by the host. :since:`Since 1.2.7 (QEMU and KVM only)` ``max_sectors`` The optional ``max_sectors`` attribute specifies the maximum amount of data in bytes that will be transferred to or from the device in a single command. The transfer length is measured in sectors, where a sector is 512 bytes. :since:`Since 1.2.7 (QEMU and KVM only)` ``ioeventfd`` The optional ``ioeventfd`` attribute specifies whether the controller should use `I/O asynchronous handling `__ or not. Accepted values are "on" and "off". :since:`Since 1.2.18` ``iothread`` Supported for controller type ``scsi`` using model ``virtio-scsi`` for ``address`` types ``pci`` and ``ccw`` :since:`since 1.3.5 (QEMU 2.4)` . The optional ``iothread`` attribute assigns the controller to an IOThread as defined by the range for the domain `iothreads <#elementsIOThreadsAllocation>`__ value. Each SCSI ``disk`` assigned to use the specified ``controller`` will utilize the same IOThread. If a specific IOThread is desired for a specific SCSI ``disk``, then multiple controllers must be defined each having a specific ``iothread`` value. The ``iothread`` value must be within the range 1 to the domain iothreads value. virtio options For virtio controllers, `Virtio-specific options <#elementsVirtio>`__ can also be set. ( :since:`Since 3.5.0` ) USB companion controllers have an optional sub-element ```` 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. Not all controller models can be used as companion controllers and libvirt might provide some sensible defaults (settings of ``master startport`` and ``function`` of an address) for some particular models. Preferred companion controllers are ``ich-uhci[123]``. :: ...

... ... PCI controllers have an optional ``model`` attribute; possible values for this attribute are - ``pci-root``, ``pci-bridge`` ( :since:`since 1.0.5` ) - ``pcie-root``, ``dmi-to-pci-bridge`` ( :since:`since 1.1.2` ) - ``pcie-root-port``, ``pcie-switch-upstream-port``, ``pcie-switch-downstream-port`` ( :since:`since 1.2.19` ) - ``pci-expander-bus``, ``pcie-expander-bus`` ( :since:`since 1.3.4` ) - ``pcie-to-pci-bridge`` ( :since:`since 4.3.0` ) The root controllers (``pci-root`` and ``pcie-root``) have an optional ``pcihole64`` element specifying how big (in kilobytes, or in the unit specified by ``pcihole64``'s ``unit`` attribute) the 64-bit PCI hole should be. Some guests (like Windows XP or Windows Server 2003) might crash when QEMU and Seabios are recent enough to support 64-bit PCI holes, unless this is disabled (set to 0). :since:`Since 1.1.2 (QEMU only)` PCI controllers also have an optional subelement ```` with an attribute ``name``. The name attribute holds the name of the specific device that qemu is emulating (e.g. "i82801b11-bridge") rather than simply the class of device ("pcie-to-pci-bridge", "pci-bridge"), which is set in the controller element's model **attribute**. In almost all cases, you should not manually add a ```` subelement to a controller, nor should you modify one that is automatically generated by libvirt. :since:`Since 1.2.19 (QEMU only).` PCI controllers also have an optional subelement ```` with the attributes and subelements listed below. These are configurable items that 1) are visible to the guest OS so must be preserved for guest ABI compatibility, and 2) are usually left to default values or derived automatically by libvirt. In almost all cases, you should not manually add a ```` subelement to a controller, nor should you modify the values in the those that are automatically generated by libvirt. :since:`Since 1.2.19 (QEMU only).` ``chassisNr`` PCI controllers that have attribute model="pci-bridge", can also have a ``chassisNr`` attribute in the ```` subelement, which is used to control QEMU's "chassis_nr" option for the pci-bridge device (normally libvirt automatically sets this to the same value as the index attribute of the pci controller). If set, chassisNr must be between 1 and 255. ``chassis`` pcie-root-port and pcie-switch-downstream-port controllers can also have a ``chassis`` attribute in the ```` subelement, which is used to set the controller's "chassis" configuration value, which is visible to the virtual machine. If set, chassis must be between 0 and 255. ``port`` pcie-root-port and pcie-switch-downstream-port controllers can also have a ``port`` attribute in the ```` subelement, which is used to set the controller's "port" configuration value, which is visible to the virtual machine. If set, port must be between 0 and 255. ``hotplug`` pcie-root-port and pcie-switch-downstream-port controllers can also have a ``hotplug`` attribute in the ```` subelement, which is used to disable hotplug/unplug of devices on a particular controller. The default setting of ``hotplug`` is ``on``; it should be set to ``off`` to disable hotplug/unplug of devices on a particular controller. :since:`Since 6.3.0` ``busNr`` pci-expander-bus and pcie-expander-bus controllers can have an optional ``busNr`` attribute (1-254). This will be the bus number of the new bus; All bus numbers between that specified and 255 will be available only for assignment to PCI/PCIe controllers plugged into the hierarchy starting with this expander bus, and bus numbers less than the specified value will be available to the next lower expander-bus (or the root-bus if there are no lower expander buses). If you do not specify a busNumber, libvirt will find the lowest existing busNumber in all other expander buses (or use 256 if there are no others) and auto-assign the busNr of that found bus - 2, which provides one bus number for the pci-expander-bus and one for the pci-bridge that is automatically attached to it (if you plan on adding more pci-bridges to the hierarchy of the bus, you should manually set busNr to a lower value). A similar algorithm is used for automatically determining the busNr attribute for pcie-expander-bus, but since the pcie-expander-bus doesn't have any built-in pci-bridge, the 2nd bus-number is just being reserved for the pcie-root-port that must necessarily be connected to the bus in order to actually plug in an endpoint device. If you intend to plug multiple devices into a pcie-expander-bus, you must connect a pcie-switch-upstream-port to the pcie-root-port that is plugged into the pcie-expander-bus, and multiple pcie-switch-downstream-ports to the pcie-switch-upstream-port, and of course for this to work properly, you will need to decrease the pcie-expander-bus' busNr accordingly so that there are enough unused bus numbers above it to accommodate giving out one bus number for the upstream-port and one for each downstream-port (in addition to the pcie-root-port and the pcie-expander-bus itself). ``node`` Some PCI controllers (``pci-expander-bus`` for the pc machine type, ``pcie-expander-bus`` for the q35 machine type and, :since:`since 3.6.0` , ``pci-root`` for the pseries machine type) can have an optional ```` subelement within the ```` subelement, which is used to set the NUMA node reported to the guest OS for that bus - the guest OS will then know that all devices on that bus are a part of the specified NUMA node (it is up to the user of the libvirt API to attach host devices to the correct pci-expander-bus when assigning them to the domain). ``index`` pci-root controllers for pSeries guests use this attribute to record the order they will show up in the guest. :since:`Since 3.6.0` For machine types which provide an implicit PCI bus, the pci-root controller with index=0 is auto-added and required to use PCI devices. pci-root has no address. PCI bridges are auto-added if there are too many devices to fit on the one bus provided by pci-root, or a PCI bus number greater than zero was specified. PCI bridges can also be specified manually, but their addresses should only refer to PCI buses provided by already specified PCI controllers. Leaving gaps in the PCI controller indexes might lead to an invalid configuration. :: ...

... For machine types which provide an implicit PCI Express (PCIe) bus (for example, the machine types based on the Q35 chipset), the pcie-root controller with index=0 is auto-added to the domain's configuration. pcie-root has also no address, provides 31 slots (numbered 1-31) that can be used to attach PCIe or PCI devices (although libvirt will never auto-assign a PCI device to a PCIe slot, it will allow manual specification of such an assignment). Devices connected to pcie-root cannot be hotplugged. If traditional PCI devices are present in the guest configuration, a ``pcie-to-pci-bridge`` controller will automatically be added: this controller, which plugs into a ``pcie-root-port``, provides 31 usable PCI slots (1-31) with hotplug support ( :since:`since 4.3.0` ). If the QEMU binary doesn't support the corresponding device, then a ``dmi-to-pci-bridge`` controller will be added instead, usually at the defacto standard location of slot=0x1e. A dmi-to-pci-bridge controller plugs into a PCIe slot (as provided by pcie-root), and itself provides 31 standard PCI slots (which also do not support device hotplug). In order to have hot-pluggable PCI slots in the guest system, a pci-bridge controller will also be automatically created and connected to one of the slots of the auto-created dmi-to-pci-bridge controller; all guest PCI devices with addresses that are auto-determined by libvirt will be placed on this pci-bridge device. ( :since:`since 1.1.2` ). Domains with an implicit pcie-root can also add controllers with ``model='pcie-root-port'``, ``model='pcie-switch-upstream-port'``, and ``model='pcie-switch-downstream-port'``. pcie-root-port is a simple type of bridge device that can connect only to one of the 31 slots on the pcie-root bus on its upstream side, and makes a single (PCIe, hotpluggable) port available on the downstream side (at slot='0'). pcie-root-port can be used to provide a single slot to later hotplug a PCIe device (but is not itself hotpluggable - it must be in the configuration when the domain is started). ( :since:`since 1.2.19` ) pcie-switch-upstream-port is a more flexible (but also more complex) device that can only plug into a pcie-root-port or pcie-switch-downstream-port on the upstream side (and only before the domain is started - it is not hot-pluggable), and provides 32 ports on the downstream side (slot='0' - slot='31') that accept only pcie-switch-downstream-port devices; each pcie-switch-downstream-port device can only plug into a pcie-switch-upstream-port on its upstream side (again, not hot-pluggable), and on its downstream side provides a single hotpluggable pcie port that can accept any standard pci or pcie device (or another pcie-switch-upstream-port), i.e. identical in function to a pcie-root-port. ( :since:`since 1.2.19` ) :: ...

... :anchor:`` 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. :: ... ... somearea somekey ... ... ``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 an offset, just pass 0. :anchor:`` Host device assignment ~~~~~~~~~~~~~~~~~~~~~~ :anchor:`` USB / PCI / SCSI devices ^^^^^^^^^^^^^^^^^^^^^^^^ USB, PCI and SCSI devices attached to the host can be passed through to the guest using the ``hostdev`` element. :since:`since after 0.4.4 for USB, 0.6.0 for PCI (KVM only) and 1.0.6 for SCSI (KVM only)` : :: ... ... or: :: ...

... or: :: ...

... or: :: ... ... or: :: ...

... ``hostdev`` The ``hostdev`` element is the main container for describing host devices. For each device, the ``mode`` is always "subsystem" and the ``type`` is one of the following values with additional attributes noted. ``usb`` USB devices are detached from the host on guest startup and reattached after the guest exits or the device is hot-unplugged. ``pci`` For PCI devices, when ``managed`` is "yes" 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", the user is responsible to call ``virNodeDeviceDetachFlags`` (or ``virsh nodedev-detach`` before starting the guest or hot-plugging the device and ``virNodeDeviceReAttach`` (or ``virsh nodedev-reattach``) after hot-unplug or stopping the guest. ``scsi`` For SCSI devices, user is responsible to make sure the device is not used by host. If supported by the hypervisor and OS, the optional ``sgio`` ( :since:`since 1.0.6` ) attribute indicates whether unprivileged SG_IO commands are filtered for the disk. Valid settings are "filtered" or "unfiltered", where the default is "filtered". The optional ``rawio`` ( :since:`since 1.2.9` ) attribute indicates whether the lun needs the rawio capability. Valid settings are "yes" or "no". See the rawio description within the `disk <#elementsDisks>`__ section. If a disk lun in the domain already has the rawio capability, then this setting not required. ``scsi_host`` :since:`since 2.5.0` For SCSI devices, user is responsible to make sure the device is not used by host. This ``type`` passes all LUNs presented by a single HBA to the guest. :since:`Since 5.2.0,` the ``model`` attribute can be specified further with "virtio-transitional", "virtio-non-transitional", or "virtio". See `Virtio transitional devices <#elementsVirtioTransitional>`__ for more details. ``mdev`` For mediated devices ( :since:`Since 3.2.0` ) the ``model`` attribute specifies the device API which determines how the host's vfio driver will expose the device to the guest. Currently, ``model='vfio-pci'``, ``model='vfio-ccw'`` ( :since:`Since 4.4.0` ) and ``model='vfio-ap'`` ( :since:`Since 4.9.0` ) is supported. `MDEV `__ section provides more information about mediated devices as well as how to create mediated devices on the host. :since:`Since 4.6.0 (QEMU 2.12)` an optional ``display`` attribute may be used to enable or disable support for an accelerated remote desktop backed by a mediated device (such as NVIDIA vGPU or Intel GVT-g) as an alternative to emulated `video devices <#elementsVideo>`__. This attribute is limited to ``model='vfio-pci'`` only. Supported values are either ``on`` or ``off`` (default is 'off'). It is required to use a `graphical framebuffer <#elementsGraphics>`__ in order to use this attribute, currently only supported with VNC, Spice and egl-headless graphics devices. :since:`Since version 5.10.0` , there is an optional ``ramfb`` attribute for devices with ``model='vfio-pci'``. Supported values are either ``on`` or ``off`` (default is 'off'). When enabled, this attribute provides a memory framebuffer device to the guest. This framebuffer will be used as a boot display when a vgpu device is the primary display. Note: There are also some implications on the usage of guest's address type depending on the ``model`` attribute, see the ``address`` element below. Note: The ``managed`` attribute is only used with ``type='pci'`` and is ignored by all the other device types, thus setting ``managed`` explicitly with other than a PCI device has the same effect as omitting it. Similarly, ``model`` attribute is only supported by mediated devices and ignored by all other device types. ``source`` The source element describes the device as seen from the host using the following mechanism to describe: ``usb`` 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 host using the ``address`` element. :since:`Since 1.0.0` , the ``source`` element of USB devices may contain ``startupPolicy`` attribute which can be used to define policy what to do if the specified host USB device is not found. The attribute accepts the following 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 ========= ===================================================================== ``pci`` PCI devices can only be described by their ``address``. :since:`Since 6.8.0 (Xen only)` , the ``source`` element of a PCI device may contain the ``writeFiltering`` attribute to control write access to the PCI configuration space. By default Xen only allows writes of known safe values to the configuration space. Setting ``writeFiltering='no'`` will allow all writes to the device's PCI configuration space. ``scsi`` SCSI devices are described by both the ``adapter`` and ``address`` elements. The ``address`` element includes a ``bus`` attribute (a 2-digit bus number), a ``target`` attribute (a 10-digit target number), and a ``unit`` attribute (a 20-digit unit number on the bus). Not all hypervisors support larger ``target`` and ``unit`` values. It is up to each hypervisor to determine the maximum value supported for the adapter. :since:`Since 1.2.8` , the ``source`` element of a SCSI device may contain the ``protocol`` attribute. When the attribute is set to "iscsi", the host device XML follows the network `disk <#elementsDisks>`__ device using the same ``name`` attribute and optionally using the ``auth`` element to provide the authentication credentials to the iSCSI server. :since:`Since 6.7.0`, the optional ``initiator`` sub-element controls the IQN of the initiator ran by the hypervisor via it's ```__ section. :since:`Since 0.8.8` for PCI devices, :since:`Since 1.0.1` for USB devices. ``rom`` The ``rom`` element is used to change how a PCI device's ROM is presented to the guest. The optional ``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:`Since 0.9.7 (QEMU and KVM only)` . The optional ``file`` attribute contains an absolute path to a binary file to be presented to the guest as the device's ROM BIOS. This can be useful, for example, to provide a PXE boot ROM for a virtual function of an sr-iov capable ethernet device (which has no boot ROMs for the VFs). :since:`Since 0.9.10 (QEMU and KVM only)` . The optional ``enabled`` attribute can be set to ``no`` to disable PCI ROM loading completely for the device; if PCI ROM loading is disabled through this attribute, attempts to tweak the loading process further using the ``bar`` or ``file`` attributes will be rejected. :since:`Since 4.3.0 (QEMU and KVM only)` . ``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 4 attributes allowing to designate the device as can be found with the ``lspci`` or with ``virsh nodedev-list``. For SCSI devices a 'drive' address type must be used. For mediated devices, which are software-only devices defining an allocation of resources on the physical parent device, the address type used must conform to the ``model`` attribute of element ``hostdev``, e.g. any address type other than PCI for ``vfio-pci`` device API or any address type other than CCW for ``vfio-ccw`` device API will result in an error. `See above <#elementsAddress>`__ for more details on the address element. ``driver`` PCI devices can have an optional ``driver`` subelement that specifies which backend driver to use for PCI device assignment. Use the ``name`` attribute to select either "vfio" (for the new VFIO device assignment backend, which is compatible with UEFI SecureBoot) or "kvm" (the legacy device assignment handled directly by the KVM kernel module) :since:`Since 1.0.5 (QEMU and KVM only, requires kernel 3.6 or newer)` . When specified, device assignment will fail if the requested method of device assignment isn't available on the host. When not specified, the default is "vfio" on systems where the VFIO driver is available and loaded, and "kvm" on older systems, or those where the VFIO driver hasn't been loaded :since:`Since 1.1.3` (prior to that the default was always "kvm"). ``readonly`` Indicates that the device is readonly, only supported by SCSI host device now. :since:`Since 1.0.6 (QEMU and KVM only)` ``shareable`` If present, this indicates the device is expected to be shared between domains (assuming the hypervisor and OS support this). Only supported by SCSI host device. :since:`Since 1.0.6` Note: Although ``shareable`` was introduced :since:`in 1.0.6` , it did not work as as expected until :since:`1.2.2` . :anchor:`` Block / character devices ^^^^^^^^^^^^^^^^^^^^^^^^^ Block / character devices from the host can be passed through to the guest using the ``hostdev`` element. This is only possible with container based virtualization. Devices are specified by a fully qualified path. :since:`since after 1.0.1 for LXC` : :: ... /dev/sdf1 ... :: ... /dev/input/event3 ... :: ... eth0 ... ``hostdev`` The ``hostdev`` element is the main container for describing host devices. For block/character device passthrough ``mode`` is always "capabilities" and ``type`` is "storage" for a block device, "misc" for a character device and "net" for a host network interface. ``source`` The source element describes the device as seen from the host. For block devices, the path to the block device in the host OS is provided in the nested "block" element, while for character devices the "char" element is used. For network interfaces, the name of the interface is provided in the "interface" element. :anchor:`` Redirected devices ~~~~~~~~~~~~~~~~~~ USB device redirection through a character device is supported :since:`since after 0.9.5 (KVM only)` : :: ... ... ``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 <#elementsConsole>`__ types, to describe the host side of the tunnel; ``type='tcp'`` or ``type='spicevmc'`` (which uses the usbredir channel of a `SPICE graphics device <#elementsGraphics>`__) are typical. The redirdev element has an optional sub-element ``

`` which can tie the device to a particular controller. Further sub-elements, such as ````, may be required according to the given type, although a ```` sub-element is not required (since the consumer of the character device is the hypervisor itself, rather than a device visible in the guest). ``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 <#elementsOSBIOS>`__ section. ( :since:`Since 1.0.1` ) ``redirfilter`` The\ ``redirfilter``\ element is used for creating the filter rule to filter out certain devices from redirection. It uses sub-element ```` to define each filter rule. ``class`` attribute is the USB Class code, for example, 0x08 represents mass storage devices. The USB device can be addressed by vendor / product id using the ``vendor`` and ``product`` attributes. ``version`` is the device revision from the bcdDevice field (not the version of the USB protocol). These four attributes are optional and ``-1`` can be used to allow any value for them. ``allow`` attribute is mandatory, 'yes' means allow, 'no' for deny. :anchor:`` 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:`Since 0.8.8` :: ... cert1 cert2 cert3 /etc/pki/nssdb/

... The ```` 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. ``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 ``

`` sub-element. ``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 ```` sub-elements. An additional sub-element ```` 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. ``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 <#elementsConsole>`__ types, to describe the host side of the tunnel; ``type='tcp'`` or ``type='spicevmc'`` (which uses the smartcard channel of a `SPICE graphics device <#elementsGraphics>`__) are typical. Further sub-elements, such as ````, may be required according to the given type, although a ```` 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 ``

``, which fine-tunes the correlation between the smartcard and a ccid bus controller, `documented above <#elementsAddress>`__. For now, qemu only supports at most one smartcard, with an address of bus=0 slot=0. :anchor:`` Network interfaces ~~~~~~~~~~~~~~~~~~ :: ... ... There are several possibilities for specifying a network interface visible to the guest. Each subsection below provides more details about common setup options. :since:`Since 1.2.10` ), the ``interface`` element property ``trustGuestRxFilters`` provides the capability for the host to detect and trust reports from the guest regarding changes to the interface mac address and receive filters by setting the attribute to ``yes``. The default setting for the attribute is ``no`` for security reasons and support depends on the guest network device model as well as the type of connection on the host - currently it is only supported for the virtio device model and for macvtap connections on the host. Each ```` element has an optional ``

`` sub-element that can tie the interface to a particular pci slot, with attribute ``type='pci'`` as `documented above <#elementsAddress>`__. :since:`Since 6.6.0` , one can force libvirt to keep the provided MAC address when it's in the reserved VMware range by adding a ``type="static"`` attribute to the ```` element. Note that this attribute is useless if the provided MAC address is outside of the reserved VMWare ranges. :since:`Since 7.3.0`, one can set the ACPI index against network interfaces. With some operating systems (eg Linux with systemd), the ACPI index is used to provide network interface device naming, that is stable across changes in PCI addresses assigned to the device. This value is required to be unique across all devices and be between 1 and (16*1024-1). :anchor:`` 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 ```` definition :since:`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 ```` element given), NAT'ing to an explicit network device or to the default route (````), routed with no NAT (````), or connected directly to one of the host's network interfaces (via macvtap) or bridge devices ((```` :since:`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 element (see `overriding the target element <#elementsNICSTargetOverride>`__). 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:`Since 0.9.4` . When a guest is running an interface of type ``network`` may include a ``portid`` attribute. This provides the UUID of an associated virNetworkPortPtr object that records the association between the domain interface and the network. This attribute is read-only since port objects are create and deleted automatically during startup and shutdown. :since:`Since 5.1.0` Also, similar to ``direct`` network connections (described below), a connection of type ``network`` may specify a ``virtualport`` element, with configuration data to be forwarded to a vepa (802.1Qbg) or 802.1Qbh compliant switch ( :since:`Since 0.8.2` ), or to an Open vSwitch virtual switch ( :since:`Since 0.9.11` ). Since the actual type of switch may vary depending on the configuration in the ```` on the host, it is acceptable to omit the virtualport ``type`` attribute, and specify attributes from multiple different virtualport types (and also to leave out certain attributes); at domain startup time, a complete ```` element will be constructed by merging together the type and attributes defined in the network and the portgroup referenced by the interface. The newly-constructed virtualport is a combination of them. The attributes from lower virtualport can't make change on the ones defined in higher virtualport. Interface takes the highest priority, portgroup is lowest priority. ( :since:`Since 0.10.0` ). For example, in order to work properly with both an 802.1Qbh switch and an Open vSwitch switch, you may choose to specify no type, but both a ``profileid`` (in case the switch is 802.1Qbh) and an ``interfaceid`` (in case the switch is Open vSwitch) (you may also omit the other attributes, such as managerid, typeid, or profileid, to be filled in from the network's ````). If you want to limit a guest to connecting only to certain types of switches, you can specify the virtualport type, but still omit some/all of the parameters - in this case if the host's network has a different type of virtualport, connection of the interface will fail. :: ... ... ... :anchor:`` 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 to the LAN. This assumes there is a bridge device on the host which has one or more of the hosts physical NICs attached. The guest VM will have an associated tun device created with a name of vnetN, which can also be overridden with the element (see `overriding the target element <#elementsNICSTargetOverride>`__). The tun device will be attached 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. On Linux systems, the bridge device is normally a standard Linux host bridge. On hosts that support Open vSwitch, it is also possible to connect to an Open vSwitch bridge device by adding a ```` to the interface definition. ( :since:`Since 0.9.11` ). The Open vSwitch type virtualport accepts two parameters in its ```` element - an ``interfaceid`` which is a standard uuid used to uniquely identify this particular interface to Open vSwitch (if you do not specify one, a random interfaceid will be generated for you when you first define the interface), and an optional ``profileid`` which is sent to Open vSwitch as the interfaces "port-profile". :: ... ... ... ... On hosts that support Open vSwitch on the kernel side and have the Midonet Host Agent configured, it is also possible to connect to the 'midonet' bridge device by adding a ```` to the interface definition. ( :since:`Since 1.2.13` ). The Midonet virtualport type requires an ``interfaceid`` attribute in its ```` element. This interface id is the UUID that specifies which port in the virtual network topology will be bound to the interface. :: ... ... ... ... :anchor:`` 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. :since:`Since 3.8.0` it is possible to override the default network address by including an ``ip`` element specifying an IPv4 address in its one mandatory attribute, ``address``. Optionally, a second ``ip`` element with a ``family`` attribute set to "ipv6" can be specified to add an IPv6 address to the interface. ``address``. Optionally, address ``prefix`` can be specified. :: ... ... ... :anchor:`` Generic ethernet connection ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Provides a means to use a new or existing tap device (or veth device pair, depending on the needs of the hypervisor driver) that is partially or wholly setup external to libvirt (either prior to the guest starting, or while the guest is being started via an optional script specified in the config). The name of the tap device can optionally be specified with the ``dev`` attribute of the ```` element. If no target dev is specified, libvirt will create a new standard tap device with a name of the pattern "vnetN", where "N" is replaced with a number. If a target dev is specified and that device doesn't exist, then a new standard tap device will be created with the exact dev name given. If the specified target dev does exist, then that existing device will be used. Usually some basic setup of the device is done by libvirt, including setting a MAC address, and the IFF_UP flag, but if the ``dev`` is a pre-existing device, and the ``managed`` attribute of the ``target`` element is also set to "no" (the default value is "yes"), even this basic setup will not be performed - libvirt will simply pass the device on to the hypervisor with no setup at all. :since:`Since 5.7.0` Using managed='no' with a pre-created tap device is useful because it permits a virtual machine managed by an unprivileged libvirtd to have emulated network devices based on tap devices. After creating/opening the tap device, an optional shell script (given in the ``path`` attribute of the ``