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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
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  <body>
    <h1>Domain XML format</h1>

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    <ul id="toc"></ul>

    <p>
      This section describes the XML format used to represent domains, there are
      variations on the format based on the kind of domains run and the options
      used to launch them. For hypervisor specific details consult the
      <a href="drivers.html">driver docs</a>
    </p>


    <h2><a name="elements">Element and attribute overview</a></h2>

    <p>
      The root element required for all virtual machines is
      named <code>domain</code>. It has two attributes, the
      <code>type</code> specifies the hypervisor used for running
      the domain. The allowed values are driver specific, but
      include "xen", "kvm", "qemu", "lxc" and "kqemu". The
      second attribute is <code>id</code> which is a unique
      integer identifier for the running guest machine. Inactive
      machines have no id value.
    </p>


    <h3><a name="elementsMetadata">General metadata</a></h3>

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<pre>
&lt;domain type='xen' id='3'&gt;
  &lt;name&gt;fv0&lt;/name&gt;
  &lt;uuid&gt;4dea22b31d52d8f32516782e98ab3fa0&lt;/uuid&gt;
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  &lt;title&gt;A short description - title - of the domain&lt;/title&gt;
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  &lt;description&gt;Some human readable description&lt;/description&gt;
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  &lt;metadata&gt;
    &lt;app1:foo xmlns:app1="http://app1.org/app1/"&gt;..&lt;/app1:foo&gt;
    &lt;app2:bar xmlns:app2="http://app1.org/app2/"&gt;..&lt;/app2:bar&gt;
  &lt;/metadata&gt;
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  ...</pre>
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    <dl>
      <dt><code>name</code></dt>
      <dd>The content of the <code>name</code> element provides
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        a short name for the virtual machine. This name should
        consist only of alpha-numeric characters and is required
        to be unique within the scope of a single host. It is
        often used to form the filename for storing the persistent
        configuration file. <span class="since">Since 0.0.1</span></dd>
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      <dt><code>uuid</code></dt>
      <dd>The content of the <code>uuid</code> element provides
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        a globally unique identifier for the virtual machine.
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        The format must be RFC 4122 compliant,
        eg <code>3e3fce45-4f53-4fa7-bb32-11f34168b82b</code>.
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        If omitted when defining/creating a new machine, a random
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        UUID is generated. It is also possible to provide the UUID
        via a <a href="#elementsSysinfo"><code>sysinfo</code></a>
        specification. <span class="since">Since 0.0.1, sysinfo
        since 0.8.7</span></dd>
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      <dt><code>title</code></dt>
      <dd>The optional element <code>title</code> provides space for a
        short description of the domain. The title should not contain
        any newlines. <span class="since">Since 0.9.10</span>.</dd>

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      <dt><code>description</code></dt>
      <dd>The content of the <code>description</code> element provides a
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        human readable description of the virtual machine. This data is not
        used by libvirt in any way, it can contain any information the user
        wants. <span class="since">Since 0.7.2</span></dd>

      <dt><code>metadata</code></dt>
      <dd>The <code>metadata</code> node can be used by applications
        to store custom metadata in the form of XML
        nodes/trees. Applications must use custom namespaces on their
        XML nodes/trees, with only one top-level element per namespace
        (if the application needs structure, they should have
        sub-elements to their namespace
        element). <span class="since">Since 0.9.10</span></dd>
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   </dl>
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    <h3><a name="elementsOS">Operating system booting</a></h3>

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

    <h4><a name="elementsOSBIOS">BIOS bootloader</a></h4>

    <p>
      Booting via the BIOS is available for hypervisors supporting
      full virtualization. In this case the BIOS has a boot order
      priority (floppy, harddisk, cdrom, network) determining where
      to obtain/find the boot image.
    </p>

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<pre>
  ...
  &lt;os&gt;
    &lt;type&gt;hvm&lt;/type&gt;
    &lt;loader&gt;/usr/lib/xen/boot/hvmloader&lt;/loader&gt;
    &lt;boot dev='hd'/&gt;
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    &lt;boot dev='cdrom'/&gt;
    &lt;bootmenu enable='yes'/&gt;
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    &lt;smbios mode='sysinfo'/&gt;
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    &lt;bios useserial='yes' rebootTimeout='0'/&gt;
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  &lt;/os&gt;
  ...</pre>
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    <dl>
      <dt><code>type</code></dt>
      <dd>The content of the <code>type</code> element specifies the
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        type of operating system to be booted in the virtual machine.
        <code>hvm</code> indicates that the OS is one designed to run
        on bare metal, so requires full virtualization. <code>linux</code>
        (badly named!) refers to an OS that supports the Xen 3 hypervisor
        guest ABI. There are also two optional attributes, <code>arch</code>
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        specifying the CPU architecture to virtualization,
        and <code>machine</code> referring to the machine
        type. The <a href="formatcaps.html">Capabilities XML</a>
        provides details on allowed values for
        these. <span class="since">Since 0.0.1</span></dd>
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      <dt><code>loader</code></dt>
      <dd>The optional <code>loader</code> tag refers to a firmware blob
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        used to assist the domain creation process. At this time, it is
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        only needed by Xen fully virtualized
        domains. <span class="since">Since 0.1.0</span></dd>
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      <dt><code>boot</code></dt>
      <dd>The <code>dev</code> attribute takes one of the values "fd", "hd",
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        "cdrom" or "network" and is used to specify the next boot device
        to consider. The <code>boot</code> element can be repeated multiple
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        times to setup a priority list of boot devices to try in turn.
        Multiple devices of the same type are sorted according to their
        targets while preserving the order of buses. After defining the
        domain, its XML configuration returned by libvirt (through
        virDomainGetXMLDesc) lists devices in the sorted order. Once sorted,
        the first device is marked as bootable. Thus, e.g., a domain
        configured to boot from "hd" with vdb, hda, vda, and hdc disks
        assigned to it will boot from vda (the sorted list is vda, vdb, hda,
        hdc). Similar domain with hdc, vda, vdb, and hda disks will boot from
        hda (sorted disks are: hda, hdc, vda, vdb). It can be tricky to
        configure in the desired way, which is why per-device boot elements
        (see <a href="#elementsDisks">disks</a>,
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        <a href="#elementsNICS">network interfaces</a>, and
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        <a href="#elementsHostDev">USB and PCI devices</a> sections below) were
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        introduced and they are the preferred way providing full control over
        booting order. The <code>boot</code> element and per-device boot
        elements are mutually exclusive. <span class="since">Since 0.1.3,
        per-device boot since 0.8.8</span>
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      </dd>
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      <dt><code>bootmenu</code></dt>
      <dd> Whether or not to enable an interactive boot menu prompt on guest
      startup. The <code>enable</code> attribute can be either "yes" or "no".
      If not specified, the hypervisor default is used. <span class="since">
      Since 0.8.3</span>
      </dd>
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      <dt><code>smbios</code></dt>
      <dd>How to populate SMBIOS information visible in the guest.
      The <code>mode</code> attribute must be specified, and is either
      "emulate" (let the hypervisor generate all values), "host" (copy
      all of Block 0 and Block 1, except for the UUID, from the host's
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      SMBIOS values;
      the <a href="html/libvirt-libvirt.html#virConnectGetSysinfo">
      <code>virConnectGetSysinfo</code></a> call can be
      used to see what values are copied), or "sysinfo" (use the values in
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      the <a href="#elementsSysinfo">sysinfo</a> element).  If not
      specified, the hypervisor default is used. <span class="since">
      Since 0.8.7</span>
      </dd>
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      <dt><code>bios</code></dt>
      <dd>This element has attribute <code>useserial</code> with possible
        values <code>yes</code> or <code>no</code>. It enables or disables
        Serial Graphics Adapter which allows users to see BIOS messages
        on a serial port. Therefore, one needs to have
        <a href="#elementCharSerial">serial port</a> defined.
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        <span class="since">Since 0.9.4</span>.
        <span class="since">Since 0.10.2 (QEMU only)</span> there is
        another attribute, <code>rebootTimeout</code> 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 <code>65535</code> and special
        value <code>-1</code> disables the reboot.
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      </dd>
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    </dl>

    <h4><a name="elementsOSBootloader">Host bootloader</a></h4>

    <p>
      Hypervisors employing paravirtualization do not usually emulate
      a BIOS, and instead the host is responsible to kicking off the
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      operating system boot. This may use a pseudo-bootloader in the
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      host to provide an interface to choose a kernel for the guest.
      An example is <code>pygrub</code> with Xen.
    </p>

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<pre>
  ...
  &lt;bootloader&gt;/usr/bin/pygrub&lt;/bootloader&gt;
  &lt;bootloader_args&gt;--append single&lt;/bootloader_args&gt;
  ...</pre>
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    <dl>
      <dt><code>bootloader</code></dt>
      <dd>The content of the <code>bootloader</code> element provides
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        a fully qualified path to the bootloader executable in the
        host OS. This bootloader will be run to choose which kernel
        to boot. The required output of the bootloader is dependent
        on the hypervisor in use. <span class="since">Since 0.1.0</span></dd>
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      <dt><code>bootloader_args</code></dt>
      <dd>The optional <code>bootloader_args</code> element allows
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        command line arguments to be passed to the bootloader.
        <span class="since">Since 0.2.3</span>
        </dd>
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    </dl>

    <h4><a name="elementsOSKernel">Direct kernel boot</a></h4>

    <p>
      When installing a new guest OS it is often useful to boot directly
      from a kernel and initrd stored in the host OS, allowing command
      line arguments to be passed directly to the installer. This capability
      is usually available for both para and full virtualized guests.
    </p>

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<pre>
  ...
  &lt;os&gt;
    &lt;type&gt;hvm&lt;/type&gt;
    &lt;loader&gt;/usr/lib/xen/boot/hvmloader&lt;/loader&gt;
    &lt;kernel&gt;/root/f8-i386-vmlinuz&lt;/kernel&gt;
    &lt;initrd&gt;/root/f8-i386-initrd&lt;/initrd&gt;
    &lt;cmdline&gt;console=ttyS0 ks=http://example.com/f8-i386/os/&lt;/cmdline&gt;
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    &lt;dtb&gt;/root/ppc.dtb&lt;/dtb&gt;
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  &lt;/os&gt;
  ...</pre>
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    <dl>
      <dt><code>type</code></dt>
      <dd>This element has the same semantics as described earlier in the
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        <a href="#elementsOSBIOS">BIOS boot section</a></dd>
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      <dt><code>loader</code></dt>
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      <dd>This element has the same semantics as described earlier in the
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        <a href="#elementsOSBIOS">BIOS boot section</a></dd>
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      <dt><code>kernel</code></dt>
      <dd>The contents of this element specify the fully-qualified path
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        to the kernel image in the host OS.</dd>
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      <dt><code>initrd</code></dt>
      <dd>The contents of this element specify the fully-qualified path
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        to the (optional) ramdisk image in the host OS.</dd>
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      <dt><code>cmdline</code></dt>
      <dd>The contents of this element specify arguments to be passed to
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        the kernel (or installer) at boottime. This is often used to
        specify an alternate primary console (eg serial port), or the
        installation media source / kickstart file</dd>
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      <dt><code>dtb</code></dt>
      <dd>The contents of this element specify the fully-qualified path
        to the (optional) device tree binary (dtb) image in the host OS.
        <span class="since">Since 1.0.4</span></dd>
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    </dl>

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    <h4><a name="eleemntsOSContainer">Container boot</a></h4>

    <p>
      When booting a domain using container based virtualization, instead
      of a kernel / boot image, a path to the init binary is required, using
      the <code>init</code> element. By default this will be launched with
      no arguments. To specify the initial argv, use the <code>initarg</code>
      element, repeated as many time as is required. The <code>cmdline</code>
      element, if set will be used to provide an equivalent to <code>/proc/cmdline</code>
      but will not effect init argv.
    </p>

    <pre>
  &lt;os&gt;
    &lt;type arch='x86_64'&gt;exe&lt;/type&gt;
    &lt;init&gt;/bin/systemd&lt;/init&gt;
    &lt;initarg&gt;--unit&lt;/initarg&gt;
    &lt;initarg&gt;emergency.service&lt;/initarg&gt;
  &lt;/os&gt;
    </pre>


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    <p>
      If you want to enable user namespace,set the <code>idmap</code> element.
      the <code>uid</code> and <code>gid</code> elements have three attributes:
    </p>

    <dl>
      <dt><code>start</code></dt>
      <dd>First user id in container.</dd>
      <dt><code>target</code></dt>
      <dd>The first user id in container will be mapped to this target user
          id in host.</dd>
      <dt><code>count</code></dt>
      <dd>How many users in container being allowed to map to host's user.</dd>
    </dl>

    <pre>
  &lt;idmap&gt;
    &lt;uid start='0' target='1000' count='10'/&gt;
    &lt;gid start='0' target='1000' count='10'/&gt;
  &lt;/idmap&gt;
    </pre>


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    <h3><a name="elementsSysinfo">SMBIOS System Information</a></h3>

    <p>
      Some hypervisors allow control over what system information is
      presented to the guest (for example, SMBIOS fields can be
      populated by a hypervisor and inspected via
      the <code>dmidecode</code> command in the guest).  The
      optional <code>sysinfo</code> element covers all such categories
      of information. <span class="since">Since 0.8.7</span>
    </p>

<pre>
  ...
  &lt;os&gt;
    &lt;smbios mode='sysinfo'/&gt;
    ...
  &lt;/os&gt;
  &lt;sysinfo type='smbios'&gt;
    &lt;bios&gt;
      &lt;entry name='vendor'&gt;LENOVO&lt;/entry&gt;
    &lt;/bios&gt;
    &lt;system&gt;
      &lt;entry name='manufacturer'&gt;Fedora&lt;/entry&gt;
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      &lt;entry name='product'&gt;Virt-Manager&lt;/entry&gt;
      &lt;entry name='version'&gt;0.9.4&lt;/entry&gt;
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    &lt;/system&gt;
  &lt;/sysinfo&gt;
  ...</pre>

    <p>
      The <code>sysinfo</code> element has a mandatory
      attribute <code>type</code> that determine the layout of
      sub-elements, with supported values of:
    </p>

    <dl>
      <dt><code>smbios</code></dt>
      <dd>Sub-elements call out specific SMBIOS values, which will
      affect the guest if used in conjunction with
      the <code>smbios</code> sub-element of
      the <a href="#elementsOS"><code>os</code></a> element.  Each
      sub-element of <code>sysinfo</code> names a SMBIOS block, and
      within those elements can be a list of <code>entry</code>
      elements that describe a field within the block.  The following
      blocks and entries are recognized:
        <dl>
          <dt><code>bios</code></dt>
          <dd>
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            This is block 0 of SMBIOS, with entry names drawn from:
            <dl>
               <dt><code>vendor</code></dt>
               <dd>BIOS Vendor's Name</dd>
               <dt><code>version</code></dt>
               <dd>BIOS Version</dd>
               <dt><code>date</code></dt>
               <dd>BIOS release date. If supplied, is in either mm/dd/yy or
                   mm/dd/yyyy format. If the year portion of the string is
                   two digits, the year is assumed to be 19yy.</dd>
               <dt><code>release</code></dt>
               <dd>System BIOS Major and Minor release number values
                   concatenated together as one string separated by
                   a period, for example, 10.22.</dd>
           </dl>
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          </dd>
          <dt><code>system</code></dt>
          <dd>
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            This is block 1 of SMBIOS, with entry names drawn from:
            <dl>
                <dt><code>manufacturer</code></dt>
                <dd>Manufacturer of BIOS</dd>
                <dt><code>product</code></dt>
                <dd>Product Name</dd>
                <dt><code>version</code></dt>
                <dd>Version of the product</dd>
                <dt><code>serial</code></dt>
                <dd>Serial number</dd>
                <dt><code>uuid</code></dt>
                <dd>Universal Unique ID number. If this entry is provided
                alongside a top-level
                <a href="#elementsMetadata"><code>uuid</code></a> element,
                then the two values must match.</dd>
                <dt><code>sku</code></dt>
                <dd>SKU number to identify a particular configuration.</dd>
                <dt><code>family</code></dt>
                <dd>Identify the family a particular computer belongs to.</dd>
            </dl>
            NB: Incorrectly supplied entries in either the <code>bios</code>
            or <code>system</code> blocks will be ignored without error.
            Other than <code>uuid</code> validation and <code>date</code>
            format checking, all values are passed as strings to the
            hypervisor driver.
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          </dd>
        </dl>
      </dd>
    </dl>

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    <h3><a name="elementsCPUAllocation">CPU Allocation</a></h3>
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<pre>
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&lt;domain&gt;
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  ...
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  &lt;vcpu placement='static' cpuset="1-4,^3,6" current="1"&gt;2&lt;/vcpu&gt;
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  ...
&lt;/domain&gt;
</pre>
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    <dl>
      <dt><code>vcpu</code></dt>
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      <dd>The content of this element defines the maximum number of virtual
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        CPUs allocated for the guest OS, which must be between 1 and
        the maximum supported by the hypervisor.  <span class="since">Since
        0.4.4</span>, this element can contain an optional
        <code>cpuset</code> attribute, which is a comma-separated
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        list of physical CPU numbers that domain process and virtual CPUs
        can be pinned to by default. (NB: The pinning policy of domain
        process and virtual CPUs can be specified separately by
        <code>cputune</code>. If attribute <code>emulatorpin</code>
        of <code>cputune</code> is specified, <code>cpuset</code>
        specified by <code>vcpu</code> here will be ingored; Similarly,
        For virtual CPUs which has <code>vcpupin</code> specified,
        <code>cpuset</code> specified by <code>cpuset</code> here
        will be ignored; For virtual CPUs which doesn't have
        <code>vcpupin</code> specified, it will be pinned to the physical
        CPUs specified by <code>cpuset</code> here).
        Each element in that list is either a single CPU number,
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        a range of CPU numbers, or a caret followed by a CPU number to
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        be excluded from a previous range.  <span class="since">Since
        0.8.5</span>, the optional attribute <code>current</code> can
        be used to specify whether fewer than the maximum number of
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        virtual CPUs should be enabled.  <span class="since">Since
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        0.9.11 (QEMU and KVM only)</span>, the optional attribute
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        <code>placement</code> can be used to indicate the CPU placement
        mode for domain process, its value can be either "static" or
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        "auto", defaults to <code>placement</code> of <code>numatune</code>,
         or "static" if <code>cpuset</code> is specified. "auto" indicates
        the domain process will be pinned to the advisory nodeset from querying
        numad, and the value of attribute <code>cpuset</code> will be ignored
        if it's specified. If both <code>cpuset</code> and <code>placement</code>
        are not specified, or if <code>placement</code> is "static", but no
        <code>cpuset</code> is specified, the domain process will be pinned to
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        all the available physical CPUs.
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      </dd>
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    </dl>


    <h3><a name="elementsCPUTuning">CPU Tuning</a></h3>

<pre>
&lt;domain&gt;
  ...
  &lt;cputune&gt;
    &lt;vcpupin vcpu="0" cpuset="1-4,^2"/&gt;
    &lt;vcpupin vcpu="1" cpuset="0,1"/&gt;
    &lt;vcpupin vcpu="2" cpuset="2,3"/&gt;
    &lt;vcpupin vcpu="3" cpuset="0,4"/&gt;
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    &lt;emulatorpin cpuset="1-3"/&gt;
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    &lt;shares&gt;2048&lt;/shares&gt;
    &lt;period&gt;1000000&lt;/period&gt;
    &lt;quota&gt;-1&lt;/quota&gt;
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    &lt;emulator_period&gt;1000000&lt;/emulator_period&gt;
    &lt;emulator_quota&gt;-1&lt;/emulator_quota&gt;
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  &lt;/cputune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
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      <dt><code>cputune</code></dt>
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      <dd>
         The optional <code>cputune</code> element provides details
         regarding the cpu tunable parameters for the domain.
         <span class="since">Since 0.9.0</span>
      </dd>
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      <dt><code>vcpupin</code></dt>
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      <dd>
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        The optional <code>vcpupin</code> element specifies which of host's
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        physical CPUs the domain VCPU will be pinned to. If this is omitted,
        and attribute <code>cpuset</code> of element <code>vcpu</code> is
        not specified, the vCPU is pinned to all the physical CPUs by default.
        It contains two required attributes, the attribute <code>vcpu</code>
        specifies vcpu id, and the attribute <code>cpuset</code> is same as
        attribute <code>cpuset</code> of element <code>vcpu</code>.
        (NB: Only qemu driver support)
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        <span class="since">Since 0.9.0</span>
       </dd>
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       <dt><code>emulatorpin</code></dt>
       <dd>
         The optional <code>emulatorpin</code> element specifies which of host
         physical CPUs the "emulator", a subset of a domain not including vcpu,
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         will be pinned to. If this is omitted, and attribute
         <code>cpuset</code> of element <code>vcpu</code> is not specified,
         "emulator" is pinned to all the physical CPUs by default. It contains
         one required attribute <code>cpuset</code> specifying which physical
         CPUs to pin to. NB, <code>emulatorpin</code> is not allowed if
         attribute <code>placement</code> of element <code>vcpu</code> is
         "auto".
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       </dd>
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      <dt><code>shares</code></dt>
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      <dd>
        The optional <code>shares</code> element specifies the proportional
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        weighted share for the domain. If this is omitted, it defaults to
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        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
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        2048 will get twice as much CPU time as a VM configured with value 1024.
        <span class="since">Since 0.9.0</span>
      </dd>
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      <dt><code>period</code></dt>
      <dd>
        The optional <code>period</code> element specifies the enforcement
        interval(unit: microseconds). Within <code>period</code>, each vcpu of
        the domain will not be allowed to consume more than <code>quota</code>
        worth of runtime. The value should be in range [1000, 1000000]. A period
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        with value 0 means no value.
        <span class="since">Only QEMU driver support since 0.9.4, LXC since
        0.9.10</span>
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      </dd>
      <dt><code>quota</code></dt>
      <dd>
        The optional <code>quota</code> element specifies the maximum allowed
        bandwidth(unit: microseconds). A domain with <code>quota</code> as any
        negative value indicates that the domain has infinite bandwidth, which
        means that it is not bandwidth controlled. The value should be in range
        [1000, 18446744073709551] or less than 0. A quota with value 0 means no
        value. You can use this feature to ensure that all vcpus run at the same
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        speed.
        <span class="since">Only QEMU driver support since 0.9.4, LXC since
        0.9.10</span>
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      </dd>
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      <dt><code>emulator_period</code></dt>
      <dd>
        The optional <code>emulator_period</code> element specifies the enforcement
        interval(unit: microseconds). Within <code>emulator_period</code>, emulator
        threads(those excluding vcpus) of the domain will not be allowed to consume
        more than <code>emulator_quota</code> worth of runtime. The value should be
        in range [1000, 1000000]. A period with value 0 means no value.
        <span class="since">Only QEMU driver support since 0.10.0</span>
      </dd>
      <dt><code>emulator_quota</code></dt>
      <dd>
        The optional <code>emulator_quota</code> element specifies the maximum
        allowed bandwidth(unit: microseconds) for domain's emulator threads(those
        excluding vcpus). A domain with <code>emulator_quota</code> as any negative
        value indicates that the domain has infinite bandwidth for emulator threads
        (those excluding vcpus), 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.
        <span class="since">Only QEMU driver support since 0.10.0</span>
      </dd>

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    </dl>


    <h3><a name="elementsMemoryAllocation">Memory Allocation</a></h3>

<pre>
&lt;domain&gt;
  ...
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  &lt;memory unit='KiB'&gt;524288&lt;/memory&gt;
  &lt;currentMemory unit='KiB'&gt;524288&lt;/currentMemory&gt;
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  ...
&lt;/domain&gt;
</pre>

    <dl>
      <dt><code>memory</code></dt>
      <dd>The maximum allocation of memory for the guest at boot time.
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        The units for this value are determined by the optional
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        attribute <code>unit</code>, which defaults to "KiB"
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        (kibibytes, 2<sup>10</sup> or blocks of 1024 bytes).  Valid
        units are "b" or "bytes" for bytes, "KB" for kilobytes
        (10<sup>3</sup> or 1,000 bytes), "k" or "KiB" for kibibytes
        (1024 bytes), "MB" for megabytes (10<sup>6</sup> or 1,000,000
        bytes), "M" or "MiB" for mebibytes (2<sup>20</sup> or
        1,048,576 bytes), "GB" for gigabytes (10<sup>9</sup> or
        1,000,000,000 bytes), "G" or "GiB" for gibibytes
        (2<sup>30</sup> or 1,073,741,824 bytes), "TB" for terabytes
        (10<sup>12</sup> or 1,000,000,000,000 bytes), or "T" or "TiB"
        for tebibytes (2<sup>40</sup> or 1,099,511,627,776 bytes).
        However, the value will be rounded up to the nearest kibibyte
        by libvirt, and may be further rounded to the granularity
        supported by the hypervisor.  Some hypervisors also enforce a
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        minimum, such as 4000KiB.

        In the case of crash, optional attribute <code>dumpCore</code>
        can be used to control whether the guest memory should be
        included in the generated coredump or not (values "on", "off").

        <span class='since'><code>unit</code> since 0.9.11</span>,
        <span class='since'><code>dumpCore</code> since 0.10.2
        (QEMU only)</span></dd>
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      <dt><code>currentMemory</code></dt>
      <dd>The actual allocation of memory for the guest. This value can
        be less than the maximum allocation, to allow for ballooning
        up the guests memory on the fly. If this is omitted, it defaults
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        to the same value as the <code>memory</code> element.
        The <code>unit</code> attribute behaves the same as
        for <code>memory</code>.</dd>
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    </dl>


    <h3><a name="elementsMemoryBacking">Memory Backing</a></h3>

<pre>
&lt;domain&gt;
  ...
  &lt;memoryBacking&gt;
    &lt;hugepages/&gt;
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    &lt;nosharepages/&gt;
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    &lt;locked/&gt;
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  &lt;/memoryBacking&gt;
  ...
&lt;/domain&gt;
</pre>

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    <p>The optional <code>memoryBacking</code> element may contain several
      elements that influence how virtual memory pages are backed by host
      pages.</p>

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    <dl>
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      <dt><code>hugepages</code></dt>
      <dd>This tells the hypervisor that the guest should have its memory
        allocated using hugepages instead of the normal native page size.</dd>
      <dt><code>nosharepages</code></dt>
      <dd>Instructs hypervisor to disable shared pages (memory merge, KSM) for
        this domain. <span class="since">Since 1.0.6</span></dd>
      <dt><code>locked</code></dt>
      <dd>When set and supported by the hypervisor, memory pages belonging
        to the domain will be locked in host's memory and the host will not
        be allowed to swap them out.
        <span class="since">Since 1.0.6</span></dd>
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    </dl>


    <h3><a name="elementsMemoryTuning">Memory Tuning</a></h3>

<pre>
&lt;domain&gt;
  ...
  &lt;memtune&gt;
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    &lt;hard_limit unit='G'&gt;1&lt;/hard_limit&gt;
    &lt;soft_limit unit='M'&gt;128&lt;/soft_limit&gt;
    &lt;swap_hard_limit unit='G'&gt;2&lt;/swap_hard_limit&gt;
    &lt;min_guarantee unit='bytes'&gt;67108864&lt;/min_guarantee&gt;
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  &lt;/memtune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
      <dt><code>memtune</code></dt>
      <dd> The optional <code>memtune</code> element provides details
        regarding the memory tunable parameters for the domain. If this is
        omitted, it defaults to the OS provided defaults. For QEMU/KVM, the
        parameters are applied to the QEMU process as a whole. Thus, when
        counting them, one needs to add up guest RAM, guest video RAM, and
        some memory overhead of QEMU itself. The last piece is hard to
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        determine so one needs guess and try.  For each tunable, it
        is possible to designate which unit the number is in on
        input, using the same values as
        for <code>&lt;memory&gt;</code>.  For backwards
        compatibility, output is always in
        KiB.  <span class='since'><code>unit</code>
        since 0.9.11</span></dd>
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      <dt><code>hard_limit</code></dt>
      <dd> The optional <code>hard_limit</code> element is the maximum memory
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        the guest can use. The units for this value are kibibytes (i.e. blocks
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        of 1024 bytes). <strong>However, users of QEMU and KVM are strongly
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        advised not to set this limit as domain may get killed by the kernel
        if the guess is too low. To determine the memory needed for a process
        to run is an
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        <a href="http://en.wikipedia.org/wiki/Undecidable_problem">
        undecidable problem</a>.</strong></dd>
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      <dt><code>soft_limit</code></dt>
      <dd> The optional <code>soft_limit</code> element is the memory limit to
        enforce during memory contention. The units for this value are
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        kibibytes (i.e. blocks of 1024 bytes)</dd>
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      <dt><code>swap_hard_limit</code></dt>
      <dd> The optional <code>swap_hard_limit</code> element is the maximum
        memory plus swap the guest can use. The units for this value are
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        kibibytes (i.e. blocks of 1024 bytes). This has to be more than
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        hard_limit value provided</dd>
      <dt><code>min_guarantee</code></dt>
      <dd> The optional <code>min_guarantee</code> element is the guaranteed
        minimum memory allocation for the guest. The units for this value are
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        kibibytes (i.e. blocks of 1024 bytes)</dd>
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    </dl>


    <h3><a name="elementsNUMATuning">NUMA Node Tuning</a></h3>

<pre>
&lt;domain&gt;
  ...
  &lt;numatune&gt;
    &lt;memory mode="strict" nodeset="1-4,^3"/&gt;
  &lt;/numatune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
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      <dt><code>numatune</code></dt>
      <dd>
        The optional <code>numatune</code> element provides details of
        how to tune the performance of a NUMA host via controlling NUMA policy
        for domain process. NB, only supported by QEMU driver.
        <span class='since'>Since 0.9.3</span>
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      </dd>
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      <dt><code>memory</code></dt>
      <dd>
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        The optional <code>memory</code> element specifies how to allocate memory
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        for the domain process on a NUMA host. It contains several optional
        attributes. Attribute <code>mode</code> is either 'interleave',
        'strict', or 'preferred', defaults to 'strict'. Attribute
        <code>nodeset</code> specifies the NUMA nodes, using the same syntax as
        attribute <code>cpuset</code> of element <code>vcpu</code>. Attribute
        <code>placement</code> (<span class='since'>since 0.9.12</span>) can be
        used to indicate the memory placement mode for domain process, its value
        can be either "static" or "auto", defaults to <code>placement</code> of
        <code>vcpu</code>, or "static" if <code>nodeset</code> is specified.
        "auto" indicates the domain process will only allocate memory from the
        advisory nodeset returned from querying numad, and the value of attribute
        <code>nodeset</code> will be ignored if it's specified.

        If <code>placement</code> of <code>vcpu</code> is 'auto', and
        <code>numatune</code> is not specified, a default <code>numatune</code>
        with <code>placement</code> 'auto' and <code>mode</code> 'strict' will
        be added implicitly.

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        <span class='since'>Since 0.9.3</span>
      </dd>
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    </dl>

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    <h3><a name="elementsBlockTuning">Block I/O Tuning</a></h3>
<pre>
&lt;domain&gt;
  ...
  &lt;blkiotune&gt;
    &lt;weight&gt;800&lt;/weight&gt;
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    &lt;device&gt;
      &lt;path&gt;/dev/sda&lt;/path&gt;
      &lt;weight&gt;1000&lt;/weight&gt;
    &lt;/device&gt;
    &lt;device&gt;
      &lt;path&gt;/dev/sdb&lt;/path&gt;
      &lt;weight&gt;500&lt;/weight&gt;
    &lt;/device&gt;
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  &lt;/blkiotune&gt;
  ...
&lt;/domain&gt;
</pre>

    <dl>
      <dt><code>blkiotune</code></dt>
      <dd> The optional <code>blkiotune</code> element provides the ability
        to tune Blkio cgroup tunable parameters for the domain. If this is
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        omitted, it defaults to the OS provided
        defaults. <span class="since">Since 0.8.8</span></dd>
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      <dt><code>weight</code></dt>
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      <dd> The optional <code>weight</code> element is the overall I/O
        weight of the guest. The value should be in the range [100,
        1000].</dd>
      <dt><code>device</code></dt>
      <dd>The domain may have multiple <code>device</code> elements
        that further tune the weights for each host block device in
        use by the domain.  Note that
        multiple <a href="#elementsDisks">guest disks</a> can share a
        single host block device, if they are backed by files within
        the same host file system, which is why this tuning parameter
        is at the global domain level rather than associated with each
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        guest disk device (contrast this to
        the <a href="#elementsDisks"><code>&lt;iotune&gt;</code></a>
        element which can apply to an
        individual <code>&lt;disk&gt;</code>).
        Each <code>device</code> element has two
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        mandatory sub-elements, <code>path</code> describing the
        absolute path of the device, and <code>weight</code> giving
        the relative weight of that device, in the range [100,
        1000].  <span class="since">Since 0.9.8</span></dd>
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    </dl>


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    <h3><a name="resPartition">Resource partitioning</a></h3>

    <p>
      Hypervisors may allow for virtual machines to be placed into
      resource partitions, potentially with nesting of said partitions.
      The <code>resource</code> element groups together configuration
      related to resource partitioning. It currently supports a child
      element <code>partition</code> whose content defines the path
      of the resource partition in which to place the domain. If no
      partition is listed, then the domain will be placed in a default
      partition. It is the responsibility of the app/admin to ensure
      that the partition exists prior to starting the guest. Only the
      (hypervisor specific) default partition can be assumed to exist
      by default.
    </p>
<pre>
  ...
  &lt;resource&gt;
    &lt;partition&gt;/virtualmachines/production&lt;/partition&gt;
  &lt;/resource&gt;
  ...
</pre>

    <p>
      Resource partitions are currently supported by the QEMU and
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      LXC drivers, which map partition paths to cgroups directories,
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      in all mounted controllers. <span class="since">Since 1.0.5</span>
    </p>

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    <h3><a name="elementsCPU">CPU model and topology</a></h3>

    <p>
      Requirements for CPU model, its features and topology can be specified
      using the following collection of elements.
      <span class="since">Since 0.7.5</span>
    </p>

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<pre>
  ...
  &lt;cpu match='exact'&gt;
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    &lt;model fallback='allow'&gt;core2duo&lt;/model&gt;
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    &lt;vendor&gt;Intel&lt;/vendor&gt;
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    &lt;topology sockets='1' cores='2' threads='1'/&gt;
    &lt;feature policy='disable' name='lahf_lm'/&gt;
  &lt;/cpu&gt;
  ...</pre>
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<pre>
  &lt;cpu mode='host-model'&gt;
    &lt;model fallback='forbid'/&gt;
    &lt;topology sockets='1' cores='2' threads='1'/&gt;
  &lt;/cpu&gt;
  ...</pre>

<pre>
  &lt;cpu mode='host-passthrough'/&gt;
  ...</pre>

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    <p>
      In case no restrictions need to be put on CPU model and its features, a
      simpler <code>cpu</code> element can be used.
      <span class="since">Since 0.7.6</span>
    </p>

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<pre>
  ...
  &lt;cpu&gt;
    &lt;topology sockets='1' cores='2' threads='1'/&gt;
  &lt;/cpu&gt;
  ...</pre>
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    <dl>
      <dt><code>cpu</code></dt>
      <dd>The <code>cpu</code> element is the main container for describing
        guest CPU requirements. Its <code>match</code> attribute specified how
        strictly has the virtual CPU provided to the guest match these
        requirements. <span class="since">Since 0.7.6</span> the
        <code>match</code> attribute can be omitted if <code>topology</code>
        is the only element within <code>cpu</code>. Possible values for the
        <code>match</code> attribute are:

        <dl>
          <dt><code>minimum</code></dt>
          <dd>The specified CPU model and features describes the minimum
            requested CPU.</dd>
          <dt><code>exact</code></dt>
          <dd>The virtual CPU provided to the guest will exactly match the
            specification</dd>
          <dt><code>strict</code></dt>
          <dd>The guest will not be created unless the host CPU does exactly
            match the specification.</dd>
        </dl>
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        <span class="since">Since 0.8.5</span> the <code>match</code>
        attribute can be omitted and will default to <code>exact</code>.
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        <span class="since">Since 0.9.10</span>, an optional <code>mode</code>
        attribute may be used to make it easier to configure a guest CPU to be
        as close to host CPU as possible. Possible values for the
        <code>mode</code> attribute are:

        <dl>
          <dt><code>custom</code></dt>
          <dd>In this mode, the <code>cpu</code> element describes the CPU
          that should be presented to the guest. This is the default when no
          <code>mode</code> attribute is specified. This mode makes it so that
          a persistent guest will see the same hardware no matter what host
          the guest is booted on.</dd>
          <dt><code>host-model</code></dt>
          <dd>The <code>host-model</code> mode is essentially a shortcut to
          copying host CPU definition from capabilities XML into domain XML.
          Since the CPU definition is copied just before starting a domain,
          exactly the same XML can be used on different hosts while still
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          providing the best guest CPU each host supports. The
          <code>match</code> attribute can't be used in this mode. Specifying
          CPU model is not supported either, but <code>model</code>'s
          <code>fallback</code> attribute may still be used. Using the
          <code>feature</code> element, specific flags may be enabled or
          disabled specifically in addition to the host model. This may be
          used to fine tune features that can be emulated.
          <span class="since">(Since 1.1.1)</span>.
          Libvirt does not model every aspect of each CPU so
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          the guest CPU will not match the host CPU exactly. On the other
          hand, the ABI provided to the guest is reproducible. During
          migration, complete CPU model definition is transferred to the
          destination host so the migrated guest will see exactly the same CPU
          model even if the destination host contains more capable CPUs for
          the running instance of the guest; but shutting down and restarting
          the guest may present different hardware to the guest according to
          the capabilities of the new host.</dd>
          <dt><code>host-passthrough</code></dt>
          <dd>With this mode, the CPU visible to the guest should be exactly
          the same as the host CPU even in the aspects that libvirt does not
          understand. Though the downside of this mode is that the guest
          environment cannot be reproduced on different hardware. Thus, if you
          hit any bugs, you are on your own. Neither <code>model</code> nor
          <code>feature</code> elements are allowed in this mode.</dd>
        </dl>

        In both <code>host-model</code> and <code>host-passthrough</code>
        mode, the real (approximate in <code>host-passthrough</code> mode) CPU
        definition which would be used on current host can be determined by
        specifying <code>VIR_DOMAIN_XML_UPDATE_CPU</code> flag when calling
        <code>virDomainGetXMLDesc</code> API. When running a guest that might
        be prone to operating system reactivation when presented with
        different hardware, and which will be migrated between hosts with
        different capabilities, you can use this output to rewrite XML to the
        <code>custom</code> mode for more robust migration.
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      </dd>

      <dt><code>model</code></dt>
      <dd>The content of the <code>model</code> element specifies CPU model
        requested by the guest. The list of available CPU models and their
        definition can be found in <code>cpu_map.xml</code> file installed
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        in libvirt's data directory. If a hypervisor is not able to use the
        exact CPU model, libvirt automatically falls back to a closest model
        supported by the hypervisor while maintaining the list of CPU
        features. <span class="since">Since 0.9.10</span>, an optional
        <code>fallback</code> attribute can be used to forbid this behavior,
        in which case an attempt to start a domain requesting an unsupported
        CPU model will fail. Supported values for <code>fallback</code>
        attribute are: <code>allow</code> (this is the default), and
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        <code>forbid</code>. The optional <code>vendor_id</code> attribute
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        (<span class="since">Since 0.10.0</span>)  can be used to set the
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        vendor id seen by the guest. It must be exactly 12 characters long.
        If not set the vendor id of the host is used. Typical possible
        values are "AuthenticAMD" and "GenuineIntel".</dd>
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      <dt><code>vendor</code></dt>
      <dd><span class="since">Since 0.8.3</span> the content of the
        <code>vendor</code> element specifies CPU vendor requested by the
        guest. If this element is missing, the guest can be run on a CPU
        matching given features regardless on its vendor. The list of
        supported vendors can be found in <code>cpu_map.xml</code>.</dd>

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      <dt><code>topology</code></dt>
      <dd>The <code>topology</code> element specifies requested topology of
        virtual CPU provided to the guest. Three non-zero values have to be
        given for <code>sockets</code>, <code>cores</code>, and
        <code>threads</code>: total number of CPU sockets, number of cores per
        socket, and number of threads per core, respectively.</dd>

      <dt><code>feature</code></dt>
      <dd>The <code>cpu</code> element can contain zero or more
        <code>elements</code> used to fine-tune features provided by the
        selected CPU model. The list of known feature names can be found in
        the same file as CPU models. The meaning of each <code>feature</code>
        element depends on its <code>policy</code> attribute, which has to be
        set to one of the following values:

        <dl>
          <dt><code>force</code></dt>
          <dd>The virtual CPU will claim the feature is supported regardless
            of it being supported by host CPU.</dd>
          <dt><code>require</code></dt>
          <dd>Guest creation will fail unless the feature is supported by host
            CPU.</dd>
          <dt><code>optional</code></dt>
          <dd>The feature will be supported by virtual CPU if and only if it
            is supported by host CPU.</dd>
          <dt><code>disable</code></dt>
          <dd>The feature will not be supported by virtual CPU.</dd>
          <dt><code>forbid</code></dt>
          <dd>Guest creation will fail if the feature is supported by host
            CPU.</dd>
        </dl>
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        <span class="since">Since 0.8.5</span> the <code>policy</code>
        attribute can be omitted and will default to <code>require</code>.
1005 1006 1007
      </dd>
    </dl>

1008
    <p>
1009
      Guest NUMA topology can be specified using the <code>numa</code> element.
1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027
      <span class="since">Since 0.9.8</span>
    </p>

<pre>
  ...
  &lt;cpu&gt;
    ...
    &lt;numa&gt;
      &lt;cell cpus='0-3' memory='512000'/&gt;
      &lt;cell cpus='4-7' memory='512000'/&gt;
    &lt;/numa&gt;
    ...
  &lt;/cpu&gt;
  ...</pre>

    <p>
      Each <code>cell</code> element specifies a NUMA cell or a NUMA node.
      <code>cpus</code> specifies the CPU or range of CPUs that are part of
1028
      the node. <code>memory</code> specifies the node memory in kibibytes
1029 1030 1031 1032 1033 1034 1035 1036
      (i.e. blocks of 1024 bytes). Each cell or node is assigned cellid
      or nodeid in the increasing order starting from 0.
    </p>

    <p>
      This guest NUMA specification is currently available only for QEMU/KVM.
    </p>

1037
    <h3><a name="elementsEvents">Events configuration</a></h3>
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    <p>
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      It is sometimes necessary to override the default actions taken
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      on various events. Not all hypervisors support all events and actions.
      The actions may be taken as a result of calls to libvirt APIs
      <code class='docref'>virDomainReboot</code>,
      <code class='docref'>virDomainShutdown</code>, or
      <code class='docref'>virDomainShutdownFlags</code>.
      Using <code>virsh reboot</code> or <code>virsh shutdown</code> would
      also trigger the event.
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    </p>

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<pre>
  ...
  &lt;on_poweroff&gt;destroy&lt;/on_poweroff&gt;
  &lt;on_reboot&gt;restart&lt;/on_reboot&gt;
  &lt;on_crash&gt;restart&lt;/on_crash&gt;
1055
  &lt;on_lockfailure&gt;poweroff&lt;/on_lockfailure&gt;
1056
  ...</pre>
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    <p>
      The following collections of elements allow the actions to be
      specified when a guest OS triggers a lifecycle operation. A
      common use case is to force a reboot to be treated as a poweroff
      when doing the initial OS installation. This allows the VM to be
      re-configured for the first post-install bootup.
    </p>
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    <dl>
      <dt><code>on_poweroff</code></dt>
      <dd>The content of this element specifies the action to take when
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        the guest requests a poweroff.</dd>
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      <dt><code>on_reboot</code></dt>
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      <dd>The content of this element specifies the action to take when
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        the guest requests a reboot.</dd>
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      <dt><code>on_crash</code></dt>
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      <dd>The content of this element specifies the action to take when
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        the guest crashes.</dd>
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    </dl>

    <p>
      Each of these states allow for the same four possible actions.
    </p>

    <dl>
      <dt><code>destroy</code></dt>
      <dd>The domain will be terminated completely and all resources
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        released.</dd>
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      <dt><code>restart</code></dt>
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      <dd>The domain will be terminated and then restarted with
        the same configuration.</dd>
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      <dt><code>preserve</code></dt>
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      <dd>The domain will be terminated and its resource preserved
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        to allow analysis.</dd>
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      <dt><code>rename-restart</code></dt>
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      <dd>The domain will be terminated and then restarted with
        a new name.</dd>
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    </dl>

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    <p>
1097 1098 1099 1100 1101 1102 1103 1104 1105 1106
    QEMU/KVM supports the <code>on_poweroff</code> and <code>on_reboot</code>
    events handling the <code>destroy</code> and <code>restart</code> actions.
    The <code>preserve</code> action for an <code>on_reboot</code> event
    is treated as a <code>destroy</code> and the <code>rename-restart</code>
    action for an <code>on_poweroff</code> event is treated as a
    <code>restart</code> event.
    </p>

    <p>
      The <code>on_crash</code> event supports these additional
1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119
      actions <span class="since">since 0.8.4</span>.
    </p>

    <dl>
      <dt><code>coredump-destroy</code></dt>
      <dd>The crashed domain's core will be dumped, and then the
        domain will be terminated completely and all resources
        released</dd>
      <dt><code>coredump-restart</code></dt>
      <dd>The crashed domain's core will be dumped, and then the
        domain will be restarted with the same configuration</dd>
    </dl>

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    <p>
      The <code>on_lockfailure</code> element (<span class="since">since
1122
      1.0.0</span>) may be used to configure what action should be
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      taken when a lock manager loses resource locks. The following
      actions are recognized by libvirt, although not all of them need
      to be supported by individual lock managers. When no action is
      specified, each lock manager will take its default action.
    </p>
    <dl>
      <dt><code>poweroff</code></dt>
      <dd>The domain will be forcefully powered off.</dd>
      <dt><code>restart</code></dt>
      <dd>The domain will be powered off and started up again to
        reacquire its locks.</dd>
      <dt><code>pause</code></dt>
      <dd>The domain will be paused so that it can be manually resumed
        when lock issues are solved.</dd>
      <dt><code>ignore</code></dt>
      <dd>Keep the domain running as if nothing happened.</dd>
    </dl>

1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152
    <h3><a name="elementsPowerManagement">Power Management</a></h3>

    <p>
      <span class="since">Since 0.10.2</span> it is possible to
      forcibly enable or disable BIOS advertisements to the guest
      OS. (NB: Only qemu driver support)
    </p>

<pre>
  ...
  &lt;pm&gt;
    &lt;suspend-to-disk enabled='no'/&gt;
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    &lt;suspend-to-mem enabled='yes'/&gt;
1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164
  &lt;/pm&gt;
  ...</pre>

    <dl>
      <dt><code>pm</code></dt>
      <dd>These elements enable ('yes') or disable ('no') BIOS support
        for S3 (suspend-to-disk) and S4 (suspend-to-mem) ACPI sleep
        states. If nothing is specified, then the hypervisor will be
        left with its default value.</dd>
    </dl>

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    <h3><a name="elementsFeatures">Hypervisor features</a></h3>

    <p>
      Hypervisors may allow certain CPU / machine features to be
      toggled on/off.
    </p>

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<pre>
  ...
  &lt;features&gt;
    &lt;pae/&gt;
    &lt;acpi/&gt;
    &lt;apic/&gt;
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    &lt;hap/&gt;
1179
    &lt;privnet/&gt;
1180
    &lt;hyperv&gt;
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      &lt;relaxed state='on'/&gt;
1182
      &lt;vapic state='on'/&gt;
1183
      &lt;spinlocks state='on' retries='4096'/&gt;
1184 1185
    &lt;/hyperv&gt;

1186 1187
  &lt;/features&gt;
  ...</pre>
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    <p>
      All features are listed within the <code>features</code>
      element, omitting a togglable feature tag turns it off.
      The available features can be found by asking
      for the <a href="formatcaps.html">capabilities XML</a>,
      but a common set for fully virtualized domains are:
    </p>

    <dl>
      <dt><code>pae</code></dt>
      <dd>Physical address extension mode allows 32-bit guests
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        to address more than 4 GB of memory.</dd>
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      <dt><code>acpi</code></dt>
      <dd>ACPI is useful for power management, for example, with
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        KVM guests it is required for graceful shutdown to work.
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      </dd>
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      <dt><code>apic</code></dt>
      <dd>APIC allows the use of programmable IRQ
1207 1208 1209
      management. <span class="since">Since 0.10.2 (QEMU only)</span> there is
      an optional attribute <code>eoi</code> with values <code>on</code>
      and <code>off</code> which toggles the availability of EOI (End of
1210 1211
      Interrupt) for the guest.
      </dd>
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      <dt><code>hap</code></dt>
      <dd>Enable use of Hardware Assisted Paging if available in
        the hardware.
      </dd>
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      <dt><code>viridian</code></dt>
      <dd>Enable Viridian hypervisor extensions for paravirtualizing
        guest operating systems
      </dd>
1220 1221 1222 1223 1224 1225
      <dt><code>privnet</code></dt>
      <dd>Always create a private network namespace. This is
        automatically set if any interface devices are defined.
        This feature is only relevant for container based
        virtualization drivers, such as LXC.
      </dd>
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      <dt><code>hyperv</code></dt>
      <dd>Enable various features improving behavior of guests
        running Microsoft Windows.
      <table class="top_table">
        <tr>
          <th>Feature</th>
          <th>Description</th>
          <th>Value</th>
1234
          <th>Since</th>
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        </tr>
        <tr>
          <td>relaxed</td>
          <td>Relax contstraints on timers</td>
          <td> on, off</td>
1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252
          <td><span class="since">1.0.0 (QEMU only)</span></td>
        </tr>
        <tr>
          <td>vapic</td>
          <td>Enable virtual APIC</td>
          <td>on, off</td>
          <td><span class="since">1.1.0 (QEMU only)</span></td>
        </tr>
        <tr>
          <td>spinlocks</td>
          <td>Enable spinlock support</td>
          <td>on, off; retries - at least 4095</td>
          <td><span class="since">1.1.0 (QEMU only)</span></td>
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        </tr>
      </table>
      </dd>
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    </dl>

    <h3><a name="elementsTime">Time keeping</a></h3>

    <p>
      The guest clock is typically initialized from the host clock.
      Most operating systems expect the hardware clock to be kept
      in UTC, and this is the default. Windows, however, expects
      it to be in so called 'localtime'.
    </p>

1267 1268
<pre>
  ...
1269 1270 1271
  &lt;clock offset='localtime'&gt;
    &lt;timer name='rtc' tickpolicy='catchup' track='guest'&gt;
      &lt;catchup threshold='123' slew='120' limit='10000'/&gt;
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    &lt;/timer&gt;
1273
    &lt;timer name='pit' tickpolicy='delay'/&gt;
1274
  &lt;/clock&gt;
1275
  ...</pre>
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    <dl>
      <dt><code>clock</code></dt>
1279
      <dd>
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        <p>The <code>offset</code> attribute takes four possible
          values, allowing fine grained control over how the guest
          clock is synchronized to the host. NB, not all hypervisors
          support all modes.</p>
        <dl>
          <dt><code>utc</code></dt>
          <dd>
            The guest clock will always be synchronized to UTC when
1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298
            booted.
            <span class="since">Since 0.9.11</span> 'utc' mode can be converted
            to 'variable' mode, which can be controlled by using the
            <code>adjustment</code> attribute. If the value is 'reset', the
            conversion is never done (not all hypervisors can
            synchronize to UTC on each boot; use of 'reset' will cause
            an error on those hypervisors). A numeric value
            forces the conversion to 'variable' mode using the value as the
            initial adjustment. The default <code>adjustment</code> is
            hypervisor specific.
          </dd>
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          <dt><code>localtime</code></dt>
          <dd>
            The guest clock will be synchronized to the host's configured
            timezone when booted, if any.
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            <span class="since">Since 0.9.11,</span> the <code>adjustment</code>
            attribute behaves the same as in 'utc' mode.
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          </dd>
          <dt><code>timezone</code></dt>
          <dd>
            The guest clock will be synchronized to the requested timezone
            using the <code>timezone</code> attribute.
            <span class="since">Since 0.7.7</span>
          </dd>
          <dt><code>variable</code></dt>
          <dd>
            The guest clock will have an arbitrary offset applied
1315 1316
            relative to UTC or localtime, depending on the <code>basis</code>
            attribute. The delta relative to UTC (or localtime) is specified
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            in seconds, using the <code>adjustment</code> attribute.
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            The guest is free to adjust the RTC over time and expect
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            that it will be honored at next reboot. This is in
            contrast to 'utc' and 'localtime' mode (with the optional
            attribute adjustment='reset'), where the RTC adjustments are
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            lost at each reboot. <span class="since">Since 0.7.7</span>
1323 1324
            <span class="since">Since 0.9.11</span> the <code>basis</code>
            attribute can be either 'utc' (default) or 'localtime'.
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          </dd>
        </dl>
        <p>
          A <code>clock</code> may have zero or more
          <code>timer</code>sub-elements. <span class="since">Since
          0.8.0</span>
        </p>
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      </dd>
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      <dt><code>timer</code></dt>
      <dd>
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        <p>
          Each timer element requires a <code>name</code> attribute,
          and has other optional attributes that depend on
          the <code>name</code> specified.  Various hypervisors
          support different combinations of attributes.
        </p>
        <dl>
          <dt><code>name</code></dt>
          <dd>
            The <code>name</code> attribute selects which timer is
1345 1346 1347 1348
            being modified, and can be one of
            "platform" (currently unsupported),
            "hpet" (libxl, xen, qemu), "kvmclock" (qemu),
            "pit" (qemu), "rtc" (qemu), or "tsc" (libxl).
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          </dd>
          <dt><code>track</code></dt>
          <dd>
            The <code>track</code> attribute specifies what the timer
            tracks, and can be "boot", "guest", or "wall".
            Only valid for <code>name="rtc"</code>
            or <code>name="platform"</code>.
          </dd>
          <dt><code>tickpolicy</code></dt>
          <dd>
1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384
            <p>
            The <code>tickpolicy</code> attribute determines what
            happens whens QEMU misses a deadline for injecting a
            tick to the guest:
            </p>
            <dl>
              <dt><code>delay</code></dt>
              <dd>Continue to deliver ticks at the normal rate.
                The guest time will be delayed due to the late
                tick</dd>
              <dt><code>catchup</code></dt>
              <dd>Deliver ticks at a higher rate to catch up
                with the missed tick. The guest time should
                not be delayed once catchup is complete.</dd>
              <dt><code>merge</code></dt>
              <dd>Merge the missed tick(s) into one tick and
                inject. The guest time may be delayed, depending
                on how the OS reacts to the merging of ticks</dd>
              <dt><code>discard</code></dt>
              <dd>Throw away the missed tick(s) and continue
                with future injection normally. The guest time
                may be delayed, unless the OS has explicit
                handling of lost ticks</dd>
            </dl>
            <p>If the policy is "catchup", there can be further details in
            the <code>catchup</code> sub-element.</p>
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            <dl>
              <dt><code>catchup</code></dt>
              <dd>
                The <code>catchup</code> element has three optional
                attributes, each a positive integer.  The attributes
                are <code>threshold</code>, <code>slew</code>,
                and <code>limit</code>.
              </dd>
            </dl>
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            <p>
              Note that hypervisors are not required to support all policies across all time sources
            </p>
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          </dd>
          <dt><code>frequency</code></dt>
          <dd>
            The <code>frequency</code> attribute is an unsigned
            integer specifying the frequency at
            which <code>name="tsc"</code> runs.
          </dd>
          <dt><code>mode</code></dt>
          <dd>
            The <code>mode</code> attribute controls how
            the <code>name="tsc"</code> timer is managed, and can be
            "auto", "native", "emulate", "paravirt", or "smpsafe".
            Other timers are always emulated.
          </dd>
          <dt><code>present</code></dt>
          <dd>
            The <code>present</code> attribute can be "yes" or "no" to
            specify whether a particular timer is available to the guest.
          </dd>
        </dl>
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      </dd>
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    </dl>

    <h3><a name="elementsDevices">Devices</a></h3>

    <p>
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      The final set of XML elements are all used to describe devices
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      provided to the guest domain. All devices occur as children
      of the main <code>devices</code> element.
      <span class="since">Since 0.1.3</span>
    </p>

1429 1430 1431 1432 1433 1434
<pre>
  ...
  &lt;devices&gt;
    &lt;emulator&gt;/usr/lib/xen/bin/qemu-dm&lt;/emulator&gt;
  &lt;/devices&gt;
  ...</pre>
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    <dl>
      <dt><code>emulator</code></dt>
      <dd>
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        The contents of the <code>emulator</code> element specify
        the fully qualified path to the device model emulator binary.
        The <a href="formatcaps.html">capabilities XML</a> specifies
        the recommended default emulator to use for each particular
        domain type / architecture combination.
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      </dd>
    </dl>

    <h4><a name="elementsDisks">Hard drives, floppy disks, CDROMs</a></h4>

    <p>
      Any device that looks like a disk, be it a floppy, harddisk,
      cdrom, or paravirtualized driver is specified via the <code>disk</code>
      element.
    </p>

1455 1456 1457
<pre>
  ...
  &lt;devices&gt;
1458
    &lt;disk type='file' snapshot='external'&gt;
1459
      &lt;driver name="tap" type="aio" cache="default"/&gt;
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      &lt;source file='/var/lib/xen/images/fv0' startupPolicy='optional'&gt;
1461 1462
        &lt;seclabel relabel='no'/&gt;
      &lt;/source&gt;
1463
      &lt;target dev='hda' bus='ide'/&gt;
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      &lt;iotune&gt;
        &lt;total_bytes_sec&gt;10000000&lt;/total_bytes_sec&gt;
        &lt;read_iops_sec&gt;400000&lt;/read_iops_sec&gt;
        &lt;write_iops_sec&gt;100000&lt;/write_iops_sec&gt;
      &lt;/iotune&gt;
1469
      &lt;boot order='2'/&gt;
1470 1471 1472 1473
      &lt;encryption type='...'&gt;
        ...
      &lt;/encryption&gt;
      &lt;shareable/&gt;
1474 1475 1476
      &lt;serial&gt;
        ...
      &lt;/serial&gt;
1477
    &lt;/disk&gt;
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      ...
    &lt;disk type='network'&gt;
1480
      &lt;driver name="qemu" type="raw" io="threads" ioeventfd="on" event_idx="off"/&gt;
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      &lt;source protocol="sheepdog" name="image_name"&gt;
        &lt;host name="hostname" port="7000"/&gt;
      &lt;/source&gt;
      &lt;target dev="hdb" bus="ide"/&gt;
1485
      &lt;boot order='1'/&gt;
1486
      &lt;transient/&gt;
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      &lt;address type='drive' controller='0' bus='1' unit='0'/&gt;
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    &lt;/disk&gt;
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    &lt;disk type='network'&gt;
      &lt;driver name="qemu" type="raw"/&gt;
      &lt;source protocol="rbd" name="image_name2"&gt;
        &lt;host name="hostname" port="7000"/&gt;
      &lt;/source&gt;
      &lt;target dev="hdd" bus="ide"/&gt;
      &lt;auth username='myuser'&gt;
        &lt;secret type='ceph' usage='mypassid'/&gt;
      &lt;/auth&gt;
    &lt;/disk&gt;
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    &lt;disk type='block' device='cdrom'&gt;
      &lt;driver name='qemu' type='raw'/&gt;
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      &lt;target dev='hdc' bus='ide' tray='open'/&gt;
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      &lt;readonly/&gt;
    &lt;/disk&gt;
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    &lt;disk type='network' device='cdrom'&gt;
      &lt;driver name='qemu' type='raw'/&gt;
      &lt;source protocol="http" name="url_path"&gt;
        &lt;host name="hostname" port="80"/&gt;
      &lt;/source&gt;
      &lt;target dev='hdc' bus='ide' tray='open'/&gt;
      &lt;readonly/&gt;
    &lt;/disk&gt;
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    &lt;disk type='block' device='lun'&gt;
      &lt;driver name='qemu' type='raw'/&gt;
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      &lt;source dev='/dev/sda'/&gt;
      &lt;target dev='sda' bus='scsi'/&gt;
      &lt;address type='drive' controller='0' bus='0' target='3' unit='0'/&gt;
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    &lt;/disk&gt;
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    &lt;disk type='block' device='disk'&gt;
      &lt;driver name='qemu' type='raw'/&gt;
      &lt;source dev='/dev/sda'/&gt;
      &lt;geometry cyls='16383' heads='16' secs='63' trans='lba'/&gt;
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      &lt;blockio logical_block_size='512' physical_block_size='4096'/&gt;
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      &lt;target dev='hda' bus='ide'/&gt;
    &lt;/disk&gt;
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    &lt;disk type='volume' device='disk'&gt;
      &lt;driver name='qemu' type='raw'/&gt;
      &lt;source pool='blk-pool0' volume='blk-pool0-vol0'/&gt;
      &lt;target dev='hda' bus='ide'/&gt;
    &lt;/disk&gt;
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    &lt;disk type='network' device='disk'&gt;
      &lt;driver name='qemu' type='raw'/&gt;
      &lt;source protocol='iscsi' name='iqn.2013-07.com.example:iscsi-nopool/2'&gt;
        &lt;host name='example.com' port='3260'/&gt;
      &lt;/source&gt;
      &lt;auth username='myuser'&gt;
        &lt;secret type='chap' usage='libvirtiscsi'/&gt;
      &lt;/auth&gt;
      &lt;target dev='vda' bus='virtio'/&gt;
    &lt;/disk&gt;
    &lt;disk type='network' device='lun'&gt;
      &lt;driver name='qemu' type='raw'/&gt;
      &lt;source protocol='iscsi' name='iqn.2013-07.com.example:iscsi-nopool/1'&gt;
       iqn.2013-07.com.example:iscsi-pool
        &lt;host name='example.com' port='3260'/&gt;
      &lt;/source&gt;
      &lt;auth username='myuser'&gt;
        &lt;secret type='chap' usage='libvirtiscsi'/&gt;
      &lt;/auth&gt;
      &lt;target dev='sda' bus='scsi'/&gt;
    &lt;/disk&gt;
    &lt;disk type='volume' device='disk'&gt;
      &lt;driver name='qemu' type='raw'/&gt;
      &lt;source pool='iscsi-pool' volume='unit:0:0:1' mode='host'/&gt;
      &lt;auth username='myuser'&gt;
        &lt;secret type='chap' usage='libvirtiscsi'/&gt;
      &lt;/auth&gt;
      &lt;target dev='vda' bus='virtio'/&gt;
    &lt;/disk&gt;
    &lt;disk type='volume' device='disk'&gt;
      &lt;driver name='qemu' type='raw'/&gt;
      &lt;source pool='iscsi-pool' volume='unit:0:0:2' mode='direct'/&gt;
      &lt;auth username='myuser'&gt;
        &lt;secret type='chap' usage='libvirtiscsi'/&gt;
      &lt;/auth&gt;
      &lt;target dev='vda' bus='virtio'/&gt;
    &lt;/disk&gt;
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  &lt;/devices&gt;
  ...</pre>
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    <dl>
      <dt><code>disk</code></dt>
      <dd>The <code>disk</code> element is the main container for describing
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      disks (<span class="since">since 0.0.3</span>).
        <dl>
          <dt><code>type</code> attribute
          <span class="since">since 0.0.3</span></dt>
            <dd>
            Valid values are "file", "block",
            "dir" (<span class="since">since 0.7.5</span>),
            "network" (<span class="since">since 0.8.7</span>), or
            "volume" (<span class="since">since 1.0.5</span>)
            and refer to the underlying source for the disk.
            </dd>
          <dt><code>device</code> attribute
          <span class="since">since 0.1.4</span></dt>
            <dd>
            Indicates how the disk is to be exposed to the guest OS. Possible
            values for this attribute are "floppy", "disk", "cdrom", and "lun",
            defaulting to "disk".
            <p>
            Using "lun" (<span class="since">since 0.9.10</span>) is only
            valid when type is "block" and the target element's "bus"
            attribute is "virtio", and behaves identically to "disk",
            except that generic SCSI commands from the guest are accepted
            and passed through to the physical device. Also note that
            device='lun' will only be recognized for actual raw devices,
            but never for individual partitions or LVM partitions (in those
            cases, the kernel will reject the generic SCSI commands, making
            it identical to device='disk').
            </p>
            </dd>
          <dt><code>rawio</code> attribute
          <span class="since">since 0.9.10</span></dt>
            <dd>
            Indicates whether the disk is needs rawio capability; valid
            settings are "yes" or "no" (default is "no"). If any one disk
            in a domain has rawio='yes', rawio capability will be enabled
            for all disks in the domain (because, in the case of QEMU, this
            capability can only be set on a per-process basis). This attribute
            is only valid when device is "lun". NB, <code>rawio</code> intends
            to confine the capability per-device, however, current QEMU
            implementation gives the domain process broader capability
            than that (per-process basis, affects all the domain disks).
            To confine the capability as much as possible for QEMU driver
            as this stage, <code>sgio</code> is recommended, it's more
            secure than <code>rawio</code>.
            </dd>
          <dt><code>sgio</code> attribute
          <span class="since">since 1.0.2</span></dt>
            <dd>
            Indicates whether the kernel will filter unprivileged
            SG_IO commands for the disk, valid settings are "filtered" or
            "unfiltered". Defaults to "filtered". Similar to <code>rawio</code>,
            <code>sgio</code> is only valid for device 'lun'.
            </dd>
          <dt><code>snapshot</code> attribute
          <span class="since">since 0.9.5</span></dt>
            <dd>
            Indicates the default behavior of the disk during disk snapshots:
            "internal" requires a file format such as qcow2 that can store
            both the snapshot and the data changes since the snapshot;
            "external" will separate the snapshot from the live data; and
            "no" means the disk will not participate in snapshots. Read-only
            disks default to "no", while the default for other disks depends
            on the hypervisor's capabilities.  Some hypervisors allow a
            per-snapshot choice as well, during
            <a href="formatsnapshot.html">domain snapshot creation</a>.
            Not all snapshot modes are supported; for example,
            <code>snapshot='yes'</code> with a transient disk generally
            does not make sense.
            </dd>
        </dl>
      </dd>
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      <dt><code>source</code></dt>
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      <dd>Representation of the disk <code>source</code> depends on the
      disk <code>type</code> attribute value as follows:
          <dl>
            <dt><code>type='file'</code>
            <span class="since">since 0.0.3</span></dt>
              <dd>
              The <code>file</code> attribute specifies the fully-qualified
              path to the file holding the disk.
              </dd>
            <dt><code>type='block'</code>
            <span class="since">since 0.0.3</span></dt>
              <dd>
              The <code>dev</code> attribute specifies the path to the
              host device to serve as the disk.
              </dd>
            <dt><code>type='dir'</code>
            <span class="since">since 0.7.5</span></dt>
              <dd>
              The <code>dir</code> attribute specifies the fully-qualified path
              to the directory to use as the disk.
              </dd>
            <dt><code>type='network'</code>
            <span class="since">since 0.8.7</span></dt>
              <dd>
              The <code>protocol</code> attribute specifies the protocol to
              access to the requested image. Possible values are "nbd",
              "iscsi", "rbd", "sheepdog" or "gluster".  If the
              <code>protocol</code> attribute is "rbd", "sheepdog" or
              "gluster", an additional attribute <code>name</code> is
              mandatory to specify which volume/image will be used. For "nbd",
              the <code>name</code> attribute is optional. For "iscsi"
              (<span class="since">since 1.0.4</span>), the <code>name</code>
              attribute may include a logical unit number, separated from the
              target's name by a slash (e.g.,
              <code>iqn.2013-07.com.example:iscsi-pool/1</code>). If not
              specified, the default LUN is zero.
              </dd>
            <dt><code>type='volume'</code>
            <span class="since">since 1.0.5</span></dt>
              <dd>
              The underlying disk source is represented by attributes
              <code>pool</code> and <code>volume</code>. Attribute
              <code>pool</code> specifies the name of the
              <a href="formatstorage.html">storage pool</a> (managed
              by libvirt) where the disk source resides. Attribute
              <code>volume</code> specifies the name of storage volume (managed
              by libvirt) used as the disk source. The value for the
              <code>volume</code> attribute will be the output from the "Name"
              column of a <code>virsh vol-list [pool-name]</code> command.
              <p>
              Use the attribute <code>mode</code>
              (<span class="since">since 1.1.1</span>) to indicate how to
              represent the LUN as the disk source. Valid values are
              "direct" and "host". If <code>mode</code> is not specified,
              the default is to use "host".

              Using "direct" as the <code>mode</code> value indicates to use
              the <a href="formatstorage.html">storage pool's</a>
              <code>source</code> element <code>host</code> attribute as
              the disk source to generate the libiscsi URI (e.g.
              'file=iscsi://example.com:3260/iqn.2013-07.com.example:iscsi-pool/1').

              Using "host" as the <code>mode</code> value indicates to use the
              LUN's path as it shows up on host (e.g.
              'file=/dev/disk/by-path/ip-example.com:3260-iscsi-iqn.2013-07.com.example:iscsi-pool-lun-1').
              </p>
              </dd>
          </dl>
        With "file", "block", and "volume", one or more optional
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        sub-elements <code>seclabel</code>, <a href="#seclabel">described
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        below</a> (and <span class="since">since 0.9.9</span>), can be
        used to override the domain security labeling policy for just
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        that source file. (NB, for "volume" type disk, <code>seclabel</code>
        is only valid when the specified storage volume is of 'file' or
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        'block' type).
        <p>
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        When the disk <code>type</code> is "network", the <code>source</code>
        may have zero or more <code>host</code> sub-elements used to
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        specify the hosts to connect.
        </p>
        <p>
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        For a "file" or "volume" disk type which represents a cdrom or floppy
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        (the <code>device</code> attribute), it is possible to define
        policy what to do with the disk if the source file is not accessible.
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        (NB, <code>startupPolicy</code> is not valid for "volume" disk unless
         the specified storage volume is of "file" type). This is done by the
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        <code>startupPolicy</code> attribute
        (<span class="since">since 0.9.7</span>),
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        accepting these values:
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        </p>
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        <table class="top_table">
          <tr>
            <td> mandatory </td>
            <td> fail if missing for any reason (the default) </td>
          </tr>
          <tr>
            <td> requisite </td>
            <td> fail if missing on boot up,
                 drop if missing on migrate/restore/revert </td>
          </tr>
          <tr>
            <td> optional </td>
            <td> drop if missing at any start attempt </td>
          </tr>
        </table>
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        <p>
        <span class="since">Since 1.1.2</span> the <code>startupPolicy</code>
        is extended to support hard disks besides cdrom and floppy. On guest
        cold bootup, if a certain disk is not accessible or its disk chain is
        broken, with startupPolicy 'optional' the guest will drop this disk.
        This feature doesn't support migration currently.
        </p>
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        </dd>
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      <dt><code>mirror</code></dt>
      <dd>
        This element is present if the hypervisor has started a block
        copy operation (via the <code>virDomainBlockCopy</code> API),
        where the mirror location in attribute <code>file</code> will
        eventually have the same contents as the source, and with the
        file format in attribute <code>format</code> (which might
        differ from the format of the source).  If
        attribute <code>ready</code> is present, then it is known the
        disk is ready to pivot; otherwise, the disk is probably still
        copying.  For now, this element only valid in output; it is
        ignored on input.  <span class="since">Since 0.9.12</span>
      </dd>
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      <dt><code>target</code></dt>
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      <dd>The <code>target</code> element controls the bus / device
        under which the disk is exposed to the guest
        OS. The <code>dev</code> attribute indicates the "logical"
        device name. The actual device name specified is not
        guaranteed to map to the device name in the guest OS. Treat it
        as a device ordering hint.  The optional <code>bus</code>
        attribute specifies the type of disk device to emulate;
        possible values are driver specific, with typical values being
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        "ide", "scsi", "virtio", "xen", "usb" or "sata". If omitted, the bus
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        type is inferred from the style of the device name (e.g. a device named
        'sda' will typically be exported using a SCSI bus). The optional
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        attribute <code>tray</code> indicates the tray status of the
        removable disks (i.e. CDROM or Floppy disk), the value can be either
        "open" or "closed", defaults to "closed". NB, the value of
        <code>tray</code> could be updated while the domain is running.
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        <span class="since">Since 0.0.3; <code>bus</code> attribute since 0.4.3;
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        <code>tray</code> attribute since 0.9.11; "usb" attribute value since
        after 0.4.4; "sata" attribute value since 0.9.7</span>
      </dd>
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      <dt><code>iotune</code></dt>
      <dd>The optional <code>iotune</code> element provides the
        ability to provide additional per-device I/O tuning, with
        values that can vary for each device (contrast this to
        the <a href="#elementsBlockTuning"><code>&lt;blkiotune&gt;</code></a>
        element, which applies globally to the domain).  Currently,
        the only tuning available is Block I/O throttling for qemu.
        This element has optional sub-elements; any sub-element not
        specified or given with a value of 0 implies no
        limit.  <span class="since">Since 0.9.8</span>
        <dl>
          <dt><code>total_bytes_sec</code></dt>
          <dd>The optional <code>total_bytes_sec</code> element is the
            total throughput limit in bytes per second.  This cannot
            appear with <code>read_bytes_sec</code>
            or <code>write_bytes_sec</code>.</dd>
          <dt><code>read_bytes_sec</code></dt>
          <dd>The optional <code>read_bytes_sec</code> element is the
            read throughput limit in bytes per second.</dd>
          <dt><code>write_bytes_sec</code></dt>
          <dd>The optional <code>write_bytes_sec</code> element is the
            write throughput limit in bytes per second.</dd>
          <dt><code>total_iops_sec</code></dt>
          <dd>The optional <code>total_iops_sec</code> element is the
            total I/O operations per second.  This cannot
            appear with <code>read_iops_sec</code>
            or <code>write_iops_sec</code>.</dd>
          <dt><code>read_iops_sec</code></dt>
          <dd>The optional <code>read_iops_sec</code> element is the
            read I/O operations per second.</dd>
          <dt><code>write_iops_sec</code></dt>
          <dd>The optional <code>write_iops_sec</code> element is the
            write I/O operations per second.</dd>
        </dl>
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      </dd>
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      <dt><code>driver</code></dt>
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      <dd>
        The optional driver element allows specifying further details
        related to the hypervisor driver used to provide the disk.
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        <span class="since">Since 0.1.8</span>
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        <ul>
          <li>
            If the hypervisor supports multiple backend drivers, then
            the <code>name</code> attribute selects the primary
            backend driver name, while the optional <code>type</code>
            attribute provides the sub-type.  For example, xen
            supports a name of "tap", "tap2", "phy", or "file", with a
            type of "aio", while qemu only supports a name of "qemu",
            but multiple types including "raw", "bochs", "qcow2", and
            "qed".
          </li>
          <li>
            The optional <code>cache</code> attribute controls the
            cache mechanism, possible values are "default", "none",
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            "writethrough", "writeback", "directsync" (like
            "writethrough", but it bypasses the host page cache) and
            "unsafe" (host may cache all disk io, and sync requests from
            guest are ignored).
            <span class="since">
              Since 0.6.0,
              "directsync" since 0.9.5,
              "unsafe" since 0.9.7
            </span>
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          </li>
          <li>
            The optional <code>error_policy</code> attribute controls
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            how the hypervisor will behave on a disk read or write
            error, possible values are "stop", "report", "ignore", and
            "enospace".<span class="since">Since 0.8.0, "report" since
            0.9.7</span> The default setting of error_policy is "report".
            There is also an
            optional <code>rerror_policy</code> that controls behavior
            for read errors only. <span class="since">Since
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            0.9.7</span>. If no rerror_policy is given, error_policy
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            is used for both read and write errors. If rerror_policy
            is given, it overrides the <code>error_policy</code> for
            read errors. Also note that "enospace" is not a valid
            policy for read errors, so if <code>error_policy</code> is
            set to "enospace" and no <code>rerror_policy</code> is
            given, the read error policy will be left at its default,
            which is "report".
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          </li>
          <li>
            The optional <code>io</code> attribute controls specific
            policies on I/O; qemu guests support "threads" and
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            "native". <span class="since">Since 0.8.8</span>
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          </li>
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          <li>
            The optional <code>ioeventfd</code> attribute allows users to
            set <a href='https://patchwork.kernel.org/patch/43390/'>
            domain I/O asynchronous handling</a> for disk device.
            The default is left to the discretion of the hypervisor.
            Accepted values are "on" and "off". Enabling this allows
            qemu to execute VM while a separate thread handles I/O.
            Typically guests experiencing high system CPU utilization
            during I/O will benefit from this. On the other hand,
            on overloaded host it could increase guest I/O latency.
            <span class="since">Since 0.9.3 (QEMU and KVM only)</span>
            <b>In general you should leave this option alone, unless you
            are very certain you know what you are doing.</b>
          </li>
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          <li>
            The optional <code>event_idx</code> attribute controls
            some aspects of device event processing. The value can be
            either 'on' or 'off' - if it is on, it will reduce the
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            number of interrupts and exits for the guest. The default
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            is determined by QEMU; usually if the feature is
            supported, default is on. In case there is a situation
            where this behavior is suboptimal, this attribute provides
            a way to force the feature off.
            <span class="since">Since 0.9.5 (QEMU and KVM only)</span>
            <b>In general you should leave this option alone, unless you
            are very certain you know what you are doing.</b>
          </li>
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          <li>
            The optional <code>copy_on_read</code> attribute controls
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            whether to copy read backing file into the image file. The
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            value can be either "on" or "off".
            Copy-on-read avoids accessing the same backing file sectors
            repeatedly and is useful when the backing file is over a slow
            network. By default copy-on-read is off.
            <span class='since'>Since 0.9.10 (QEMU and KVM only)</span>
          </li>
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          <li>
            The optional <code>discard</code> attribute controls whether
            to discard (also known as "trim" or "unmap") requests are
            ignored or passed to the filesystem. The value can be either
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            "unmap" (allow the discard request to be passed) or "ignore"
            (ignore the discard request).
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            <span class='since'>Since 1.0.6 (QEMU and KVM only)</span>
          </li>
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        </ul>
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      </dd>
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      <dt><code>boot</code></dt>
      <dd>Specifies that the disk is bootable. The <code>order</code>
        attribute determines the order in which devices will be tried during
        boot sequence. The per-device <code>boot</code> elements cannot be
        used together with general boot elements in
        <a href="#elementsOSBIOS">BIOS bootloader</a> section.
        <span class="since">Since 0.8.8</span>
      </dd>
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      <dt><code>encryption</code></dt>
      <dd>If present, specifies how the volume is encrypted.  See
        the <a href="formatstorageencryption.html">Storage Encryption</a> page
        for more information.
      </dd>
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      <dt><code>readonly</code></dt>
      <dd>If present, this indicates the device cannot be modified by
        the guest.  For now, this is the default for disks with
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        attribute <code>device='cdrom'</code>.
1941
      </dd>
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      <dt><code>shareable</code></dt>
      <dd>If present, this indicates the device is expected to be shared
          between domains (assuming the hypervisor and OS support this),
          which means that caching should be deactivated for that device.
      </dd>
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      <dt><code>transient</code></dt>
      <dd>If present, this indicates that changes to the device
        contents should be reverted automatically when the guest
        exits.  With some hypervisors, marking a disk transient
        prevents the domain from participating in migration or
        snapshots. <span class="since">Since 0.9.5</span>
      </dd>
1954 1955
      <dt><code>serial</code></dt>
      <dd>If present, this specify serial number of virtual hard drive.
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          For example, it may look
          like <code>&lt;serial&gt;WD-WMAP9A966149&lt;/serial&gt;</code>.
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          <span class="since">Since 0.7.1</span>
      </dd>
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      <dt><code>wwn</code></dt>
      <dd>If present, this element specifies the WWN (World Wide Name)
        of a virtual hard disk or CD-ROM drive. It must be composed
        of 16 hexadecimal digits.
        <span class='since'>Since 0.10.1</span>
      </dd>
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      <dt><code>vendor</code></dt>
      <dd>If present, this element specifies the vendor of a virtual hard
        disk or CD-ROM device. It must not be longer than 8 printable
        characters.
        <span class='since'>Since 1.0.1</span>
      </dd>
      <dt><code>product</code></dt>
      <dd>If present, this element specifies the product of a virtual hard
        disk or CD-ROM device. It must not be longer than 16 printable
        characters.
        <span class='since'>Since 1.0.1</span>
      </dd>
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      <dt><code>host</code></dt>
1979 1980 1981 1982 1983
      <dd>The <code>host</code> element supports 4 attributes, viz.  "name",
        "port", "transport" and "socket", which specify the hostname, the port
         number, transport type and path to socket, respectively. The meaning
         of this element and the number of the elements depend on the protocol
         attribute.
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        <table class="top_table">
          <tr>
            <th> Protocol </th>
            <th> Meaning </th>
            <th> Number of hosts </th>
1989
            <th> Default port </th>
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          </tr>
          <tr>
            <td> nbd </td>
            <td> a server running nbd-server </td>
            <td> only one </td>
1995
            <td> 10809 </td>
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          </tr>
1997 1998 1999 2000
          <tr>
            <td> iscsi </td>
            <td> an iSCSI server </td>
            <td> only one </td>
2001
            <td> 3260 </td>
2002
          </tr>
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          <tr>
            <td> rbd </td>
            <td> monitor servers of RBD </td>
            <td> one or more </td>
2007
            <td> 6789 </td>
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          </tr>
          <tr>
            <td> sheepdog </td>
            <td> one of the sheepdog servers (default is localhost:7000) </td>
            <td> zero or one </td>
2013
            <td> 7000 </td>
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          </tr>
2015 2016 2017 2018
          <tr>
            <td> gluster </td>
            <td> a server running glusterd daemon </td>
            <td> only one </td>
2019
            <td> 24007 </td>
2020
          </tr>
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        </table>
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        gluster supports "tcp", "rdma", "unix" as valid values for the
        transport attribute.  nbd supports "tcp" and "unix".  Others only
        support "tcp".  If nothing is specified, "tcp" is assumed. If the
        transport is "unix", the socket attribute specifies the path to an
        AF_UNIX socket.
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      </dd>
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      <dt><code>address</code></dt>
      <dd>If present, the <code>address</code> element ties the disk
        to a given slot of a controller (the
        actual <code>&lt;controller&gt;</code> device can often be
        inferred by libvirt, although it can
        be <a href="#elementsControllers">explicitly specified</a>).
        The <code>type</code> attribute is mandatory, and is typically
        "pci" or "drive".  For a "pci" controller, additional
        attributes for <code>bus</code>, <code>slot</code>,
2037 2038 2039 2040 2041
        and <code>function</code> must be present, as well as
        optional <code>domain</code> and <code>multifunction</code>.
        Multifunction defaults to 'off'; any other value requires
        QEMU 0.1.3 and <span class="since">libvirt 0.9.7</span>.  For a
        "drive" controller, additional attributes
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        <code>controller</code>, <code>bus</code>, <code>target</code>
        (<span class="since">libvirt 0.9.11</span>), and <code>unit</code>
        are available, each defaulting to 0.
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      </dd>
      <dt><code>auth</code></dt>
      <dd>If present, the <code>auth</code> element provides the
        authentication credentials needed to access the source.  It
        includes a mandatory attribute <code>username</code>, which
        identifies the username to use during authentication, as well
        as a sub-element <code>secret</code> with mandatory
        attribute <code>type</code>, to tie back to
        a <a href="formatsecret.html">libvirt secret object</a> that
        holds the actual password or other credentials (the domain XML
        intentionally does not expose the password, only the reference
        to the object that does manage the password).  For now, the
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        known secret <code>type</code>s are "ceph", for Ceph RBD
        network sources, and "iscsi", for CHAP authentication of iSCSI
        targets.  Both require either a <code>uuid</code> attribute
        with the UUID of the secret object, or a <code>usage</code>
        attribute matching the key that was specified in the
        secret object.  <span class="since">libvirt 0.9.7</span>
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      </dd>
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      <dt><code>geometry</code></dt>
      <dd>The optional <code>geometry</code> element provides the
        ability to override geometry settings. This mostly useful for
        S390 DASD-disks or older DOS-disks.  <span class="since">0.10.0</span>
        <dl>
          <dt><code>cyls</code></dt>
          <dd>The <code>cyls</code> attribute is the
            number of cylinders. </dd>
          <dt><code>heads</code></dt>
          <dd>The <code>heads</code> attribute is the
            number of heads. </dd>
          <dt><code>secs</code></dt>
          <dd>The <code>secs</code> attribute is the
            number of sectors per track. </dd>
          <dt><code>trans</code></dt>
          <dd>The optional <code>trans</code> attribute is the
            BIOS-Translation-Modus (none, lba or auto)</dd>
        </dl>
      </dd>
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      <dt><code>blockio</code></dt>
      <dd>If present, the <code>blockio</code> element allows
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        to override any of the block device properties listed below.
        <span class="since">Since 0.10.2 (QEMU and KVM)</span>
        <dl>
          <dt><code>logical_block_size</code></dt>
          <dd>The logical block size the disk will report to the guest
            OS. For Linux this would be the value returned by the
            BLKSSZGET ioctl and describes the smallest units for disk
            I/O.
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          </dd>
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          <dt><code>physical_block_size</code></dt>
          <dd>The physical block size the disk will report to the guest
            OS. For Linux this would be the value returned by the
            BLKPBSZGET ioctl and describes the disk's hardware sector
            size which can be relevant for the alignment of disk data.
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          </dd>
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        </dl>
      </dd>
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    </dl>

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    <h4><a name="elementsFilesystems">Filesystems</a></h4>

    <p>
      A directory on the host that can be accessed directly from the guest.
      <span class="since">since 0.3.3, since 0.8.5 for QEMU/KVM</span>
    </p>

<pre>
  ...
  &lt;devices&gt;
    &lt;filesystem type='template'&gt;
      &lt;source name='my-vm-template'/&gt;
      &lt;target dir='/'/&gt;
    &lt;/filesystem&gt;
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    &lt;filesystem type='mount' accessmode='passthrough'&gt;
2119
      &lt;driver type='path' wrpolicy='immediate'/&gt;
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      &lt;source dir='/export/to/guest'/&gt;
      &lt;target dir='/import/from/host'/&gt;
      &lt;readonly/&gt;
    &lt;/filesystem&gt;
2124 2125 2126 2127 2128 2129 2130
    &lt;filesystem type='file' accessmode='passthrough'&gt;
      &lt;driver name='loop' type='raw'/&gt;
      &lt;driver type='path' wrpolicy='immediate'/&gt;
      &lt;source file='/export/to/guest.img'/&gt;
      &lt;target dir='/import/from/host'/&gt;
      &lt;readonly/&gt;
    &lt;/filesystem&gt;
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    ...
  &lt;/devices&gt;
  ...</pre>

    <dl>
      <dt><code>filesystem</code></dt>
      <dd>

      The filesystem attribute <code>type</code> specifies the type of the
      <code>source</code>. The possible values are:

        <dl>
        <dt><code>type='mount'</code></dt>
        <dd>
        A host directory to mount in the guest. Used by LXC,
        OpenVZ <span class="since">(since 0.6.2)</span>
        and QEMU/KVM <span class="since">(since 0.8.5)</span>.
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        This is the default <code>type</code> if one is not specified.
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        This mode also has an optional
        sub-element <code>driver</code>, with an
        attribute <code>type='path'</code>
        or <code>type='handle'</code> <span class="since">(since
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        0.9.7)</span>. The driver block has an optional attribute
        <code>wrpolicy</code> that further controls interaction with
        the host page cache; omitting the attribute gives default behavior,
        while the value <code>immediate</code> means that a host writeback
        is immediately triggered for all pages touched during a guest file
        write operation <span class="since">(since 0.9.10)</span>.
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        </dd>
        <dt><code>type='template'</code></dt>
        <dd>
        OpenVZ filesystem template. Only used by OpenVZ driver.
        </dd>
        <dt><code>type='file'</code></dt>
        <dd>
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        A host file will be treated as an image and mounted in
        the guest. The filesystem format will be autodetected.
        Only used by LXC driver.
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        </dd>
        <dt><code>type='block'</code></dt>
        <dd>
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        A host block device to mount in the guest. The filesystem
        format will be autodetected. Only used by LXC driver
        <span class="since">(since 0.9.5)</span>.
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        </dd>
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        <dt><code>type='ram'</code></dt>
        <dd>
          An in-memory filesystem, using memory from the host OS.
          The source element has a single attribute <code>usage</code>
          which gives the memory usage limit in kibibytes. Only used
          by LXC driver.
          <span class="since"> (since 0.9.13)</span></dd>
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        <dt><code>type='bind'</code></dt>
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        <dd>
          A directory inside the guest will be bound to another
          directory inside the guest. Only used by LXC driver
          <span class="since"> (since 0.9.13)</span></dd>
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        </dl>

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      The filesystem block has an optional attribute <code>accessmode</code>
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      which specifies the security mode for accessing the source
      <span class="since">(since 0.8.5)</span>. Currently this only works
      with <code>type='mount'</code> for the QEMU/KVM driver. The possible
      values are:

        <dl>
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        <dt><code>accessmode='passthrough'</code></dt>
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        <dd>
        The <code>source</code> is accessed with the permissions of the
2200
        user inside the guest. This is the default <code>accessmode</code> if
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        one is not specified.
        <a href="http://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02673.html">More info</a>
        </dd>
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        <dt><code>accessmode='mapped'</code></dt>
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        <dd>
        The <code>source</code> is accessed with the permissions of the
        hypervisor (QEMU process).
        <a href="http://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02673.html">More info</a>
        </dd>
2210
        <dt><code>accessmode='squash'</code></dt>
2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221
        <dd>
        Similar to 'passthrough', the exception is that failure of
        privileged operations like 'chown' are ignored. This makes a
        passthrough-like mode usable for people who run the hypervisor
        as non-root.
        <a href="http://lists.gnu.org/archive/html/qemu-devel/2010-09/msg00121.html">More info</a>
        </dd>
        </dl>

      </dd>

2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232
      <dt><code>driver</code></dt>
      <dd>
        The optional driver element allows specifying further details
        related to the hypervisor driver used to provide the filesystem.
        <span class="since">Since 1.0.6</span>
        <ul>
          <li>
            If the hypervisor supports multiple backend drivers, then
            the <code>type</code> attribute selects the primary
            backend driver name, while the <code>format</code>
            attribute provides the format type. For example, LXC
2233 2234 2235
            supports a type of "loop", with a format of "raw" or
            "nbd" with any format. QEMU supports a type of "path"
            or "handle", but no formats.
2236 2237 2238 2239
          </li>
        </ul>
      </dd>

2240 2241 2242 2243 2244
      <dt><code>source</code></dt>
      <dd>
        The resource on the host that is being accessed in the guest. The
        <code>name</code> attribute must be used with
        <code>type='template'</code>, and the <code>dir</code> attribute must
2245 2246
        be used with <code>type='mount'</code>. The <code>usage</code> attribute
        is used with <code>type='ram'</code> to set the memory limit in KB.
2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258
      </dd>

      <dt><code>target</code></dt>
      <dd>
        Where the <code>source</code> can be accessed in the guest. For
        most drivers this is an automatic mount point, but for QEMU/KVM
        this is merely an arbitrary string tag that is exported to the
        guest as a hint for where to mount.
      </dd>

      <dt><code>readonly</code></dt>
      <dd>
2259 2260 2261
        Enables exporting filesytem as a readonly mount for guest, by
        default read-write access is given (currently only works for
        QEMU/KVM driver).
2262
      </dd>
2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276

      <dt><code>space_hard_limit</code></dt>
      <dd>
        Maximum space available to this guest's filesystem.
        <span class="since">Since 0.9.13</span>
      </dd>

      <dt><code>space_soft_limit</code></dt>
      <dd>
        Maximum space available to this guest's filesystem. The container is
        permitted to exceed its soft limits for a grace period of time. Afterwards the
        hard limit is enforced.
        <span class="since">Since 0.9.13</span>
      </dd>
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    </dl>

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    <h4><a name="elementsAddress">Device Addresses</a></h4>

    <p>
      Many devices have an optional <code>&lt;address&gt;</code>
      sub-element to describe where the device is placed on the
      virtual bus presented to the guest.  If an address (or any
      optional attribute within an address) is omitted on
      input, libvirt will generate an appropriate address; but an
      explicit address is required if more control over layout is
      required.  See below for device examples including an address
      element.
    </p>

    <p>
      Every address has a mandatory attribute <code>type</code> that
      describes which bus the device is on.  The choice of which
      address to use for a given device is constrained in part by the
      device and the architecture of the guest.  For example,
      a <code>&lt;disk&gt;</code> device
      uses <code>type='disk'</code>, while
      a <code>&lt;console&gt;</code> device would
      use <code>type='pci'</code> on i686 or x86_64 guests,
      or <code>type='spapr-vio'</code> on PowerPC64 pseries guests.
      Each address type has further optional attributes that control
      where on the bus the device will be placed:
    </p>

    <dl>
      <dt><code>type='pci'</code></dt>
      <dd>PCI addresses have the following additional
        attributes: <code>domain</code> (a 2-byte hex integer, not
        currently used by qemu), <code>bus</code> (a hex value between
        0 and 0xff, inclusive), <code>slot</code> (a hex value between
        0x0 and 0x1f, inclusive), and <code>function</code> (a value
        between 0 and 7, inclusive).  Also available is
        the <code>multifunction</code> attribute, which controls
        turning on the multifunction bit for a particular
        slot/function in the PCI control register
        (<span class="since">since 0.9.7, requires QEMU
        0.13</span>). <code>multifunction</code> defaults to 'off',
        but should be set to 'on' for function 0 of a slot that will
        have multiple functions used.
      </dd>
      <dt><code>type='drive'</code></dt>
      <dd>Drive addresses have the following additional
        attributes: <code>controller</code> (a 2-digit controller
        number), <code>bus</code> (a 2-digit bus number),
2326
        <code>target</code> (a 2-digit bus number),
2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339
        and <code>unit</code> (a 2-digit unit number on the bus).
      </dd>
      <dt><code>type='virtio-serial'</code></dt>
      <dd>Each virtio-serial address has the following additional
        attributes: <code>controller</code> (a 2-digit controller
        number), <code>bus</code> (a 2-digit bus number),
        and <code>slot</code> (a 2-digit slot within the bus).
      </dd>
      <dt><code>type='ccid'</code></dt>
      <dd>A CCID address, for smart-cards, has the following
        additional attributes: <code>bus</code> (a 2-digit bus
        number), and <code>slot</code> attribute (a 2-digit slot
        within the bus).  <span class="since">Since 0.8.8.</span>
2340
      </dd>
2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355
      <dt><code>type='usb'</code></dt>
      <dd>USB addresses have the following additional
        attributes: <code>bus</code> (a hex value between 0 and 0xfff,
        inclusive), and <code>port</code> (a dotted notation of up to
        four octets, such as 1.2 or 2.1.3.1).
      </dd>
      <dt><code>type='spapr-vio'</code></dt>
      <dd>On PowerPC pseries guests, devices can be assigned to the
        SPAPR-VIO bus.  It has a flat 64-bit address space; by
        convention, devices are generally assigned at a non-zero
        multiple of 0x1000, but other addresses are valid and
        permitted by libvirt.  Each address has the following
        additional attribute: <code>reg</code> (the hex value address
        of the starting register).  <span class="since">Since
        0.9.9.</span>
2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369
      </dd>
      <dt><code>type='ccw'</code></dt>
      <dd>s390 guests with a <code>machine</code> value of
        s390-ccw-virtio use the native CCW bus for I/O devices.
        CCW bus addresses have the following additional attributes:
        <code>cssid</code> (a hex value between 0 and 0xfe, inclusive),
        <code>ssid</code> (a value between 0 and 3, inclusive) and
        <code>devno</code> (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 devices for s390 must have their
        cssid set to 0xfe in order to be recognized by the guest
        operating system.
        <span class="since">Since 1.0.4</span>
2370 2371 2372
      </dd>
    </dl>

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    <h4><a name="elementsControllers">Controllers</a></h4>

    <p>
2376 2377 2378
      Depending on the guest architecture, some device busses can
      appear more than once, with a group of virtual devices tied to a
      virtual controller.  Normally, libvirt can automatically infer such
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      controllers without requiring explicit XML markup, but sometimes
      it is necessary to provide an explicit controller element.
    </p>

<pre>
  ...
  &lt;devices&gt;
    &lt;controller type='ide' index='0'/&gt;
    &lt;controller type='virtio-serial' index='0' ports='16' vectors='4'/&gt;
    &lt;controller type='virtio-serial' index='1'&gt;
      &lt;address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/&gt;
    &lt;/controller&gt;
    ...
  &lt;/devices&gt;
  ...</pre>

    <p>
      Each controller has a mandatory attribute <code>type</code>,
2397
      which must be one of "ide", "fdc", "scsi", "sata", "usb",
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      "ccid", "virtio-serial" or "pci", and a mandatory
2399 2400 2401 2402 2403
      attribute <code>index</code> which is the decimal integer
      describing in which order the bus controller is encountered (for
      use in <code>controller</code> attributes
      of <code>&lt;address&gt;</code> elements).  The "virtio-serial"
      controller has two additional optional
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      attributes <code>ports</code> and <code>vectors</code>, which
      control how many devices can be connected through the
      controller.  A "scsi" controller has an optional
2407
      attribute <code>model</code>, which is one of "auto", "buslogic",
2408
      "ibmvscsi", "lsilogic", "lsisas1068", "lsisas1078", "virtio-scsi" or
2409 2410 2411 2412 2413 2414
      "vmpvscsi".  A "usb" controller has an optional attribute
      <code>model</code>, which is one of "piix3-uhci", "piix4-uhci", "ehci",
      "ich9-ehci1", "ich9-uhci1", "ich9-uhci2", "ich9-uhci3", "vt82c686b-uhci",
      "pci-ohci" or "nec-xhci".  Additionally,
      <span class="since">since 0.10.0</span>, if the USB bus needs to be
      explicitly disabled for the guest, <code>model='none'</code> may be
2415 2416 2417
      used.  <span class="since">Since 1.0.5</span>, no default USB controller
      will be built on s390.  The PowerPC64 "spapr-vio" addresses do not have an
      associated controller.
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    </p>

    <p>
      For controllers that are themselves devices on a PCI or USB bus,
      an optional sub-element <code>&lt;address&gt;</code> can specify
      the exact relationship of the controller to its master bus, with
2424
      semantics <a href="#elementsAddress">given above</a>.
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    </p>

2427 2428 2429 2430 2431 2432 2433
    <p>
      An optional sub-element <code>driver</code> can specify the driver
      specific options. Currently it only supports attribute <code>queues</code>
      (<span class="since">1.0.5</span>, QEMU and KVM only), which specifies the
      number of queues for the controller. For best performance, it's recommended
      to specify a value matching the number of vCPUs.
    </p>
2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449
    <p>
      USB companion controllers have an optional
      sub-element <code>&lt;master&gt;</code> to specify the exact
      relationship of the companion to its master controller.
      A companion controller is on the same bus as its master, so
      the companion <code>index</code> value should be equal.
    </p>

<pre>
  ...
  &lt;devices&gt;
    &lt;controller type='usb' index='0' model='ich9-ehci1'&gt;
      &lt;address type='pci' domain='0' bus='0' slot='4' function='7'/&gt;
    &lt;/controller&gt;
    &lt;controller type='usb' index='0' model='ich9-uhci1'&gt;
      &lt;master startport='0'/&gt;
2450
      &lt;address type='pci' domain='0' bus='0' slot='4' function='0' multifunction='on'/&gt;
2451 2452 2453
    &lt;/controller&gt;
    ...
  &lt;/devices&gt;
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  ...</pre>

    <p>
      PCI controllers have an optional <code>model</code> attribute with
2458 2459
      possible values <code>pci-root</code>, <code>pcie-root</code>,
      <code>pci-bridge</code>, or <code>dmi-to-pci-bridge</code>.
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      For machine types which provide an implicit PCI bus, the pci-root
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      controller with index=0 is auto-added and required to use PCI devices.
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      pci-root has no address.
2463 2464 2465
      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.
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      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.
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      (pci-root and pci-bridge <span class="since">since 1.0.5</span>)
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    </p>
<pre>
  ...
  &lt;devices&gt;
    &lt;controller type='pci' index='0' model='pci-root'/&gt;
    &lt;controller type='pci' index='1' model='pci-bridge'&gt;
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      &lt;address type='pci' domain='0' bus='0' slot='5' function='0' multifunction='off'/&gt;
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    &lt;/controller&gt;
  &lt;/devices&gt;
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  ...</pre>

    <p>
      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) and can only be used to attach PCIe
2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499
      devices. In order to connect standard PCI devices on a system
      which has a pcie-root controller, a pci controller
      with <code>model='dmi-to-pci-bridge'</code> is automatically
      added. A dmi-to-pci-bridge controller plugs into a PCIe slot (as
      provided by pcie-root), and itself provides 31 standard PCI
      slots (which are not hot-pluggable). 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 devices with PCI addresses that are
      auto-determined by libvirt will be placed on this pci-bridge
      device.  (<span class="since">since 1.1.2</span>).
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    </p>
<pre>
  ...
  &lt;devices&gt;
    &lt;controller type='pci' index='0' model='pcie-root'/&gt;
2505 2506 2507 2508 2509 2510
    &lt;controller type='pci' index='1' model='dmi-to-pci-bridge'&gt;
      &lt;address type='pci' domain='0' bus='0' slot='0xe' function='0'/&gt;
    &lt;/controller&gt;
    &lt;controller type='pci' index='2' model='pci-bridge'&gt;
      &lt;address type='pci' domain='0' bus='1' slot='1' function='0'/&gt;
    &lt;/controller&gt;
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  &lt;/devices&gt;
2512 2513
  ...</pre>

2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552
    <h4><a name="elementsLease">Device leases</a></h4>

    <p>
      When using a lock manager, it may be desirable to record device leases
      against a VM. The lock manager will ensure the VM won't start unless
      the leases can be acquired.
    </p>

<pre>
  ...
  &lt;devices&gt;
    ...
    &lt;lease&gt;
      &lt;lockspace&gt;somearea&lt;/lockspace&gt;
      &lt;key&gt;somekey&lt;/key&gt;
      &lt;target path='/some/lease/path' offset='1024'/&gt;
    &lt;/lease&gt;
    ...
  &lt;/devices&gt;
  ...</pre>

    <dl>
      <dt>lockspace</dt>
      <dd>This is an arbitrary string, identifying the lockspace
        within which the key is held. Lock managers may impose
        extra restrictions on the format, or length of the lockspace
        name.</dd>
      <dt>key</dt>
      <dd>This is an arbitrary string, uniquely identifying the
        lease to be acquired. Lock managers may impose extra
        restrictions on the format, or length of the key.
      </dd>
      <dt>target</dt>
      <dd>This is the fully qualified path of the file associated
        with the lockspace. The offset specifies where the lease
        is stored within the file. If the lock manager does not
        require a offset, just pass 0.
      </dd>
    </dl>
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2554 2555
    <h4><a name="elementsHostDev">Host device assignment</a></h4>

2556
    <h5><a name="elementsHostDevSubsys">USB / PCI / SCSI devices</a></h5>
2557 2558

    <p>
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      USB, PCI and SCSI devices attached to the host can be passed through
2560
      to the guest using the <code>hostdev</code> element.
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      <span class="since">since after 0.4.4 for USB, 0.6.0 for PCI(KVM only)
        and 1.0.6 for SCSI(KVM only)</span>:
2563 2564
    </p>

2565 2566 2567 2568
<pre>
  ...
  &lt;devices&gt;
    &lt;hostdev mode='subsystem' type='usb'&gt;
2569
      &lt;source startupPolicy='optional'&gt;
2570 2571 2572
        &lt;vendor id='0x1234'/&gt;
        &lt;product id='0xbeef'/&gt;
      &lt;/source&gt;
2573
      &lt;boot order='2'/&gt;
2574 2575 2576 2577
    &lt;/hostdev&gt;
  &lt;/devices&gt;
  ...</pre>

2578
    <p>or:</p>
2579 2580 2581 2582

<pre>
  ...
  &lt;devices&gt;
2583
    &lt;hostdev mode='subsystem' type='pci' managed='yes'&gt;
2584 2585 2586
      &lt;source&gt;
        &lt;address bus='0x06' slot='0x02' function='0x0'/&gt;
      &lt;/source&gt;
2587
      &lt;boot order='1'/&gt;
2588
      &lt;rom bar='on' file='/etc/fake/boot.bin'/&gt;
2589 2590
    &lt;/hostdev&gt;
  &lt;/devices&gt;
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  ...</pre>

    <p>or:</p>

<pre>
  ...
  &lt;devices&gt;
    &lt;hostdev mode='subsystem' type='scsi'&gt;
      &lt;source&gt;
        &lt;adapter name='scsi_host0'/&gt;
        &lt;address type='scsi' bus='0' target='0' unit='0'/&gt;
      &lt;/source&gt;
      &lt;readonly/&gt;
      &lt;address type='drive' controller='0' bus='0' target='0' unit='0'/&gt;
    &lt;/hostdev&gt;
  &lt;/devices&gt;
2607
  ...</pre>
2608 2609 2610 2611

    <dl>
      <dt><code>hostdev</code></dt>
      <dd>The <code>hostdev</code> element is the main container for describing
2612
        host devices. For usb device passthrough <code>mode</code> is always
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        "subsystem" and <code>type</code> is "usb" for a USB device, "pci"
        for a PCI device and "scsi" for a SCSI device. When
        <code>managed</code> is "yes" for a PCI
2616
        device, it is detached from the host before being passed on to
2617 2618 2619 2620 2621 2622 2623 2624
        the guest, and reattached to the host after the guest exits.
        If <code>managed</code> is omitted or "no", and for USB
        devices, the user is responsible to
        call <code>virNodeDeviceDettach</code> (or <code>virsh
        nodedev-dettach</code>) before starting the guest or
        hot-plugging the device,
        and <code>virNodeDeviceReAttach</code> (or <code>virsh
        nodedev-reattach</code>) after hot-unplug or stopping the
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        guest. For SCSI device, user is responsible to make sure the device
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        is not used by host.
        The optional <code>sgio</code> (<span class="since">since 1.0.6</span>)
        attribute indicates whether the kernel will filter unprivileged
        SG_IO commands for the disk, valid settings are "filtered" or
        "unfiltered". Defaults to "filtered".
      </dd>
2632 2633 2634 2635
      <dt><code>source</code></dt>
      <dd>The source element describes the device as seen from the host.
      The USB device can either be addressed by vendor / product id using the
      <code>vendor</code> and <code>product</code> elements or by the device's
2636 2637
      address on the hosts using the <code>address</code> element. PCI devices
      on the other hand can only be described by their <code>address</code>.
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      SCSI devices are described by both the <code>adapter</code> and
      <code>address</code> elements.
2640

2641
      <span class="since">Since 1.0.0</span>, the <code>source</code> element
2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660
      of USB devices may contain <code>startupPolicy</code> 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:
        <table class="top_table">
          <tr>
            <td> mandatory </td>
            <td> fail if missing for any reason (the default) </td>
          </tr>
          <tr>
            <td> requisite </td>
            <td> fail if missing on boot up,
                 drop if missing on migrate/restore/revert </td>
          </tr>
          <tr>
            <td> optional </td>
            <td> drop if missing at any start attempt </td>
          </tr>
        </table>
      </dd>
2661 2662 2663 2664 2665
      <dt><code>vendor</code>, <code>product</code></dt>
      <dd>The <code>vendor</code> and <code>product</code> elements each have an
      <code>id</code> attribute that specifies the USB vendor and product id.
      The ids can be given in decimal, hexadecimal (starting with 0x) or
      octal (starting with 0) form.</dd>
2666 2667 2668 2669 2670 2671
      <dt><code>boot</code></dt>
      <dd>Specifies that the device is bootable. The <code>order</code>
      attribute determines the order in which devices will be tried during
      boot sequence. The per-device <code>boot</code> elements cannot be
      used together with general boot elements in
      <a href="#elementsOSBIOS">BIOS bootloader</a> section.
2672 2673
      <span class="since">Since 0.8.8</span> for PCI devices,
      <span class="since">Since 1.0.1</span> for USB devices.
2674
      </dd>
2675 2676
      <dt><code>rom</code></dt>
      <dd>The <code>rom</code> element is used to change how a PCI
2677
        device's ROM is presented to the guest. The optional <code>bar</code>
2678 2679 2680 2681 2682 2683 2684
        attribute can be set to "on" or "off", and determines whether
        or not the device's ROM will be visible in the guest's memory
        map. (In PCI documentation, the "rombar" setting controls the
        presence of the Base Address Register for the ROM). If no rom
        bar is specified, the qemu default will be used (older
        versions of qemu used a default of "off", while newer qemus
        have a default of "on"). <span class="since">Since
2685 2686 2687 2688 2689 2690 2691
        0.9.7 (QEMU and KVM only)</span>. The optional
        <code>file</code> attribute is used to point to a binary file
        to be presented to the guest as the device's ROM BIOS. This
        can be useful, for example, to provide a PXE boot ROM for a
        virtual function of an sr-iov capable ethernet device (which
        has no boot ROMs for the VFs).
        <span class="since">Since 0.9.10 (QEMU and KVM only)</span>.
2692
      </dd>
2693
      <dt><code>address</code></dt>
2694 2695 2696 2697 2698 2699 2700
      <dd>The <code>address</code> element for USB devices has a
      <code>bus</code> and <code>device</code> attribute to specify the
      USB bus and device number the device appears at on the host.
      The values of these attributes can be given in decimal, hexadecimal
      (starting with 0x) or octal (starting with 0) form.
      For PCI devices the element carries 3 attributes allowing to designate
      the device as can be found with the <code>lspci</code> or
2701 2702
      with <code>virsh
      nodedev-list</code>. <a href="#elementsAddress">See above</a> for
2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718
      more details on the address element.</dd>
      <dt><code>driver</code></dt>
      <dd>
        PCI devices can have an optional <code>driver</code>
        subelement that specifies which backend driver to use for PCI
        device assignment. Use the <code>name</code> attribute to
        select either "vfio" (for the new VFIO device assignment
        backend, which is compatible with UEFI SecureBoot) or "kvm"
        (for the legacy device assignment handled directly by the KVM
        kernel module)<span class="since">Since 1.0.5 (QEMU and KVM
        only, requires kernel 3.6 or newer)</span>. Currently, "kvm"
        is the default used by libvirt when not explicitly provided,
        but since the two are functionally equivalent, this default
        could be changed in the future with no impact to domains that
        don't specify anything.
      </dd>
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      <dt><code>readonly</code></dt>
      <dd>Indicates that the device is readonly, only supported by SCSI host
        device now. <span class="since">Since 1.0.6 (QEMU and KVM only)</span>
      </dd>
2723 2724 2725 2726 2727 2728
      <dt><code>shareable</code></dt>
      <dd>If present, this indicates the device is expected to be shared
        between domains (assuming the hypervisor and OS support this).
        Only supported by SCSI host device.
        <span class="since">Since 1.0.6</span>
      </dd>
2729 2730
    </dl>

2731

2732
    <h5><a name="elementsHostDevCaps">Block / character devices</a></h5>
2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757

    <p>
      Block / character devices from the host can be passed through
      to the guest using the <code>hostdev</code> element. This is
      only possible with container based virtualization.
      <span class="since">since after 1.0.1 for LXC</span>:
    </p>

    <pre>
...
&lt;hostdev mode='capabilities' type='storage'&gt;
  &lt;source&gt;
    &lt;block&gt;/dev/sdf1&lt;/block&gt;
  &lt;/source&gt;
&lt;/hostdev&gt;
...
    </pre>

    <pre>
...
&lt;hostdev mode='capabilities' type='misc'&gt;
  &lt;source&gt;
    &lt;char&gt;/dev/input/event3&lt;/char&gt;
  &lt;/source&gt;
&lt;/hostdev&gt;
2758 2759 2760
...
    </pre>

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    <pre>
2762 2763 2764 2765 2766 2767
...
&lt;hostdev mode='capabilities' type='net'&gt;
  &lt;source&gt;
    &lt;interface&gt;eth0&lt;/interface&gt;
  &lt;/source&gt;
&lt;/hostdev&gt;
2768 2769 2770 2771 2772 2773 2774 2775
...
    </pre>

    <dl>
      <dt><code>hostdev</code></dt>
      <dd>The <code>hostdev</code> element is the main container for describing
        host devices. For block/character device passthrough <code>mode</code> is
        always "capabilities" and <code>type</code> is "block" for a block
2776 2777
        device, "char" for a character device and "net" for a host network
        interface.
2778 2779 2780 2781 2782
      </dd>
      <dt><code>source</code></dt>
      <dd>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
2783 2784
        devices the "char" element is used. For network interfaces, the
        name of the interface is provided in the "interface" element.
2785 2786 2787
      </dd>
    </dl>

2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800
    <h4><a name="elementsRedir">Redirected devices</a></h4>

    <p>
      USB device redirection through a character device is
      supported <span class="since">since after 0.9.5 (KVM
      only)</span>:
    </p>

<pre>
  ...
  &lt;devices&gt;
    &lt;redirdev bus='usb' type='tcp'&gt;
      &lt;source mode='connect' host='localhost' service='4000'/&gt;
2801
      &lt;boot order='1'/&gt;
2802
    &lt;/redirdev&gt;
2803 2804 2805 2806
    &lt;redirfilter&gt;
      &lt;usbdev class='0x08' vendor='0x1234' product='0xbeef' version='2.00' allow='yes'/&gt;
      &lt;usbdev allow='no'/&gt;
    &lt;/redirfilter&gt;
2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822
  &lt;/devices&gt;
  ...</pre>

    <dl>
      <dt><code>redirdev</code></dt>
      <dd>The <code>redirdev</code> element is the main container for
        describing redirected devices. <code>bus</code> must be "usb"
        for a USB device.

        An additional attribute <code>type</code> is required,
        matching one of the
        supported <a href="#elementsConsole">serial device</a> types,
        to describe the host side of the
        tunnel; <code>type='tcp'</code>
        or <code>type='spicevmc'</code> (which uses the usbredir
        channel of a <a href="#elementsGraphics">SPICE graphics
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        device</a>) are typical. The redirdev element has an optional
        sub-element <code>&lt;address&gt;</code> which can tie the
2825 2826 2827 2828
        device to a particular controller. Further sub-elements,
        such as <code>&lt;source&gt;</code>, may be required according
        to the given type, although a <code>&lt;target&gt;</code> sub-element
        is not required (since the consumer of the character device is
2829 2830 2831 2832 2833 2834 2835 2836 2837 2838
        the hypervisor itself, rather than a device visible in the guest).
      </dd>
      <dt><code>boot</code></dt>

      <dd>Specifies that the device is bootable.
        The <code>order</code> attribute determines the order in which
        devices will be tried during boot sequence. The per-device
        <code>boot</code> elements cannot be used together with general
        boot elements in  <a href="#elementsOSBIOS">BIOS bootloader</a> section.
        (<span class="since">Since 1.0.1</span>)
2839 2840 2841 2842
      </dd>
      <dt><code>redirfilter</code></dt>
      <dd>The<code> redirfilter </code>element is used for creating the
        filter rule to filter out certain devices from redirection.
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        It uses sub-element <code>&lt;usbdev&gt;</code> to define each filter rule.
        <code>class</code> attribute is the USB Class code, for example,
2845
        0x08 represents mass storage devices. The USB device can be addressed by
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        vendor / product id using the <code>vendor</code> and <code>product</code> attributes.
2847 2848
        <code>version</code> is the bcdDevice value of USB device, such as 1.00, 1.10 and 2.00.
        These four attributes are optional and <code>-1</code> can be used to allow
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        any value for them. <code>allow</code> attribute is mandatory,
2850 2851
        'yes' means allow, 'no' for deny.
      </dd>
2852 2853
    </dl>

2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883
    <h4><a name="elementsSmartcard">Smartcard devices</a></h4>

    <p>
      A virtual smartcard device can be supplied to the guest via the
      <code>smartcard</code> element. A USB smartcard reader device on
      the host cannot be used on a guest with simple device
      passthrough, since it will then not be available on the host,
      possibly locking the host computer when it is "removed".
      Therefore, some hypervisors provide a specialized virtual device
      that can present a smartcard interface to the guest, with
      several modes for describing how credentials are obtained from
      the host or even a from a channel created to a third-party
      smartcard provider. <span class="since">Since 0.8.8</span>
    </p>

<pre>
  ...
  &lt;devices&gt;
    &lt;smartcard mode='host'/&gt;
    &lt;smartcard mode='host-certificates'&gt;
      &lt;certificate&gt;cert1&lt;/certificate&gt;
      &lt;certificate&gt;cert2&lt;/certificate&gt;
      &lt;certificate&gt;cert3&lt;/certificate&gt;
      &lt;database&gt;/etc/pki/nssdb/&lt;/database&gt;
    &lt;/smartcard&gt;
    &lt;smartcard mode='passthrough' type='tcp'&gt;
      &lt;source mode='bind' host='127.0.0.1' service='2001'/&gt;
      &lt;protocol type='raw'/&gt;
      &lt;address type='ccid' controller='0' slot='0'/&gt;
    &lt;/smartcard&gt;
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    &lt;smartcard mode='passthrough' type='spicevmc'/&gt;
2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926
  &lt;/devices&gt;
  ...
</pre>

    <p>
      The <code>&lt;smartcard&gt;</code> element has a mandatory
      attribute <code>mode</code>.  The following modes are supported;
      in each mode, the guest sees a device on its USB bus that
      behaves like a physical USB CCID (Chip/Smart Card Interface
      Device) card.
    </p>

    <dl>
      <dt><code>mode='host'</code></dt>
      <dd>The simplest operation, where the hypervisor relays all
      requests from the guest into direct access to the host's
      smartcard via NSS.  No other attributes or sub-elements are
      required.  See below about the use of an
      optional <code>&lt;address&gt;</code> sub-element.</dd>

      <dt><code>mode='host-certificates'</code></dt>
      <dd>Rather than requiring a smartcard to be plugged into the
      host, it is possible to provide three NSS certificate names
      residing in a database on the host.  These certificates can be
      generated via the command <code>certutil -d /etc/pki/nssdb -x -t
      CT,CT,CT -S -s CN=cert1 -n cert1</code>, and the resulting three
      certificate names must be supplied as the content of each of
      three <code>&lt;certificate&gt;</code> sub-elements.  An
      additional sub-element <code>&lt;database&gt;</code> can specify
      the absolute path to an alternate directory (matching
      the <code>-d</code> option of the <code>certutil</code> command
      when creating the certificates); if not present, it defaults to
      /etc/pki/nssdb.</dd>

      <dt><code>mode='passthrough'</code></dt>
      <dd>Rather than having the hypervisor directly communicate with
      the host, it is possible to tunnel all requests through a
      secondary character device to a third-party provider (which may
      in turn be talking to a smartcard or using three certificate
      files).  In this mode of operation, an additional
      attribute <code>type</code> is required, matching one of the
      supported <a href="#elementsConsole">serial device</a> types, to
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      describe the host side of the tunnel; <code>type='tcp'</code>
      or <code>type='spicevmc'</code> (which uses the smartcard
      channel of a <a href="#elementsGraphics">SPICE graphics
      device</a>) are typical.  Further sub-elements, such
      as <code>&lt;source&gt;</code>, may be required according to the
2932 2933 2934 2935 2936 2937 2938 2939 2940
      given type, although a <code>&lt;target&gt;</code> sub-element
      is not required (since the consumer of the character device is
      the hypervisor itself, rather than a device visible in the
      guest).</dd>
    </dl>

    <p>
      Each mode supports an optional
      sub-element <code>&lt;address&gt;</code>, which fine-tunes the
2941 2942 2943
      correlation between the smartcard and a ccid bus
      controller, <a href="#elementsAddress">documented above</a>.
      For now, qemu only supports at most one
2944 2945 2946
      smartcard, with an address of bus=0 slot=0.
    </p>

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    <h4><a name="elementsNICS">Network interfaces</a></h4>

2949 2950 2951 2952 2953 2954 2955
<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='bridge'&gt;
      &lt;source bridge='xenbr0'/&gt;
      &lt;mac address='00:16:3e:5d:c7:9e'/&gt;
      &lt;script path='vif-bridge'/&gt;
2956
      &lt;boot order='1'/&gt;
2957
      &lt;rom bar='off'/&gt;
2958 2959 2960
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>
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    <p>
      There are several possibilities for specifying a network
      interface visible to the guest.  Each subsection below provides
      more details about common setup options.  Additionally,
      each <code>&lt;interface&gt;</code> element has an
      optional <code>&lt;address&gt;</code> sub-element that can tie
      the interface to a particular pci slot, with
2969 2970
      attribute <code>type='pci'</code>
      as <a href="#elementsAddress">documented above</a>.
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    </p>

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    <h5><a name="elementsNICSVirtual">Virtual network</a></h5>

    <p>
      <strong><em>
      This is the recommended config for general guest connectivity on
2978 2979 2980 2981
      hosts with dynamic / wireless networking configs (or multi-host
      environments where the host hardware details are described
      separately in a <code>&lt;network&gt;</code>
      definition <span class="since">Since 0.9.4</span>).
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      </em></strong>
    </p>

    <p>
2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012

      Provides a connection whose details are described by the named
      network definition. Depending on the virtual network's "forward
      mode" configuration, the network may be totally isolated
      (no <code>&lt;forward&gt;</code> element given), NAT'ing to an
      explicit network device or to the default route
      (<code>&lt;forward mode='nat'&gt;</code>), routed with no NAT
      (<code>&lt;forward mode='route'/&gt;</code>), or connected
      directly to one of the host's network interfaces (via macvtap)
      or bridge devices ((<code>&lt;forward
      mode='bridge|private|vepa|passthrough'/&gt;</code> <span class="since">Since
      0.9.4</span>)
    </p>
    <p>
      For networks with a forward mode of bridge, private, vepa, and
      passthrough, it is assumed that the host has any necessary DNS
      and DHCP services already setup outside the scope of libvirt. In
      the case of isolated, nat, and routed networks, DHCP and DNS are
      provided on the virtual network by libvirt, and the IP range can
      be determined by examining the virtual network config with
      '<code>virsh net-dumpxml [networkname]</code>'. There is one
      virtual network called 'default' setup out of the box which does
      NAT'ing to the default route and has an IP range
      of <code>192.168.122.0/255.255.255.0</code>. Each guest will
      have an associated tun device created with a name of vnetN,
      which can also be overridden with the &lt;target&gt; element
      (see
3013
      <a href="#elementsNICSTargetOverride">overriding the target element</a>).
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    </p>
3015 3016 3017 3018 3019 3020
    <p>
      When the source of an interface is a network,
      a <code>portgroup</code> can be specified along with the name of
      the network; one network may have multiple portgroups defined,
      with each portgroup containing slightly different configuration
      information for different classes of network
3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039
      connections. <span class="since">Since 0.9.4</span>.
    </p>
    <p>
      Also, similar to <code>direct</code> network connections
      (described below), a connection of type <code>network</code> may
      specify a <code>virtualport</code> element, with configuration
      data to be forwarded to a vepa (802.1Qbg) or 802.1Qbh compliant
      switch (<span class="since">Since 0.8.2</span>), or to an
      Open vSwitch virtual switch (<span class="since">Since
      0.9.11</span>).
    </p>
    <p>
      Since the actual type of switch may vary depending on the
      configuration in the <code>&lt;network&gt;</code> on the host,
      it is acceptable to omit the virtualport <code>type</code>
      attribute, and specify attributes from multiple different
      virtualport types (and also to leave out certain attributes); at
      domain startup time, a complete <code>&lt;virtualport&gt;</code>
      element will be constructed by merging together the type and
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      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.
3045 3046 3047
      (<span class="since">Since 0.10.0</span>). 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
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      an <code>profileid</code> (in case the switch is 802.1Qbh) and
3049 3050 3051 3052 3053 3054 3055 3056 3057
      an <code>interfaceid</code> (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 <code>&lt;virtualport&gt;</code>). 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.
3058
    </p>
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3060 3061 3062 3063 3064 3065 3066 3067
<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='network'&gt;
      &lt;source network='default'/&gt;
    &lt;/interface&gt;
    ...
    &lt;interface type='network'&gt;
3068
      &lt;source network='default' portgroup='engineering'/&gt;
3069
      &lt;target dev='vnet7'/&gt;
3070
      &lt;mac address="00:11:22:33:44:55"/&gt;
3071 3072
      &lt;virtualport&gt;
        &lt;parameters instanceid='09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f'/&gt;
3073 3074
      &lt;/virtualport&gt;

3075 3076 3077
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>
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    <h5><a name="elementsNICSBridge">Bridge to LAN</a></h5>
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    <p>
      <strong><em>
      This is the recommended config for general guest connectivity on
3084
      hosts with static wired networking configs.
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      </em></strong>
    </p>

    <p>
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      Provides a bridge from the VM directly to the LAN. This assumes
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      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
3093 3094 3095 3096 3097
      &lt;target&gt; element (see
      <a href="#elementsNICSTargetOverride">overriding the target element</a>).
      The tun device will be enslaved to the bridge. The IP range / network
      configuration is whatever is used on the LAN. This provides the guest VM
      full incoming &amp; outgoing net access just like a physical machine.
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    </p>
3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113
    <p>
      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 <code>&lt;virtualport type='openvswitch'/&gt;</code> to the
      interface definition.  (<span class="since">Since
      0.9.11</span>). The Open vSwitch type virtualport accepts two
      parameters in its <code>&lt;parameters&gt;</code> element -
      an <code>interfaceid</code> which is a standard uuid used to
      uniquely identify this particular interface to Open vSwitch (if
      you do no specify one, a random interfaceid will be generated
      for you when you first define the interface), and an
      optional <code>profileid</code> which is sent to Open vSwitch as
      the interfaces "port-profile".
    </p>
3114 3115 3116
<pre>
  ...
  &lt;devices&gt;
3117
    ...
3118 3119 3120 3121
    &lt;interface type='bridge'&gt;
      &lt;source bridge='br0'/&gt;
    &lt;/interface&gt;
    &lt;interface type='bridge'&gt;
3122
      &lt;source bridge='br1'/&gt;
3123
      &lt;target dev='vnet7'/&gt;
3124
      &lt;mac address="00:11:22:33:44:55"/&gt;
3125
    &lt;/interface&gt;
3126 3127
    &lt;interface type='bridge'&gt;
      &lt;source bridge='ovsbr'/&gt;
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      &lt;virtualport type='openvswitch'&gt;
3129 3130 3131 3132
        &lt;parameters profileid='menial' interfaceid='09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f'/&gt;
      &lt;/virtualport&gt;
    &lt;/interface&gt;
    ...
3133 3134
  &lt;/devices&gt;
  ...</pre>
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    <h5><a name="elementsNICSSlirp">Userspace SLIRP stack</a></h5>

    <p>
      Provides a virtual LAN with NAT to the outside world. The virtual
      network has DHCP &amp; DNS services and will give the guest VM addresses
      starting from <code>10.0.2.15</code>. The default router will be
      <code>10.0.2.2</code> and the DNS server will be <code>10.0.2.3</code>.
      This networking is the only option for unprivileged users who need their
      VMs to have outgoing access.
    </p>

3147 3148 3149 3150 3151 3152
<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='user'/&gt;
    ...
    &lt;interface type='user'&gt;
3153
      &lt;mac address="00:11:22:33:44:55"/&gt;
3154 3155 3156
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>
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    <h5><a name="elementsNICSEthernet">Generic ethernet connection</a></h5>

    <p>
      Provides a means for the administrator to execute an arbitrary script
      to connect the guest's network to the LAN. The guest will have a tun
      device created with a name of vnetN, which can also be overridden with the
      &lt;target&gt; element. After creating the tun device a shell script will
      be run which is expected to do whatever host network integration is
      required. By default this script is called /etc/qemu-ifup but can be
      overridden.
    </p>

3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181
<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='ethernet'/&gt;
    ...
    &lt;interface type='ethernet'&gt;
      &lt;target dev='vnet7'/&gt;
      &lt;script path='/etc/qemu-ifup-mynet'/&gt;
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>
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3183 3184 3185 3186
    <h5><a name="elementsNICSDirect">Direct attachment to physical interface</a></h5>

    <p>
      Provides direct attachment of the virtual machine's NIC to the given
3187
      physical interface of the host.
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      <span class="since">Since 0.7.7 (QEMU and KVM only)</span><br/>
3189 3190 3191
      This setup requires the Linux macvtap
      driver to be available. <span class="since">(Since Linux 2.6.34.)</span>
      One of the modes 'vepa'
3192
      ( <a href="http://www.ieee802.org/1/files/public/docs2009/new-evb-congdon-vepa-modular-0709-v01.pdf">
3193
      'Virtual Ethernet Port Aggregator'</a>), 'bridge' or 'private'
3194
      can be chosen for the operation mode of the macvtap device, 'vepa'
3195 3196
      being the default mode. The individual modes cause the delivery of
      packets to behave as follows:
3197 3198
    </p>

3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209
    <dl>
      <dt><code>vepa</code></dt>
      <dd>All VMs' packets are sent to the external bridge. Packets
      whose destination is a VM on the same host as where the
      packet originates from are sent back to the host by the VEPA
      capable bridge (today's bridges are typically not VEPA capable).</dd>
      <dt><code>bridge</code></dt>
      <dd>Packets whose destination is on the same host as where they
      originate from are directly delivered to the target macvtap device.
      Both origin and destination devices need to be in bridge mode
      for direct delivery. If either one of them is in <code>vepa</code> mode,
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      a VEPA capable bridge is required.</dd>
3211 3212 3213 3214 3215 3216
      <dt><code>private</code></dt>
      <dd>All packets are sent to the external bridge and will only be
      delivered to a target VM on the same host if they are sent through an
      external router or gateway and that device sends them back to the
      host. This procedure is followed if either the source or destination
      device is in <code>private</code> mode.</dd>
3217 3218 3219 3220 3221 3222 3223
      <dt><code>passthrough</code></dt>
      <dd>This feature attaches a virtual function of a SRIOV capable
      NIC directly to a VM without losing the migration capability.
      All packets are sent to the VF/IF of the configured network device.
      Depending on the capabilities of the device additional prerequisites or
      limitations may apply; for example, on Linux this requires
      kernel 2.6.38 or newer. <span class="since">Since 0.9.2</span></dd>
3224 3225
    </dl>

3226 3227 3228 3229 3230 3231 3232 3233 3234 3235
<pre>
  ...
  &lt;devices&gt;
    ...
    &lt;interface type='direct'&gt;
      &lt;source dev='eth0' mode='vepa'/&gt;
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>

3236 3237 3238 3239
    <p>
      The network access of direct attached virtual machines can be
      managed by the hardware switch to which the physical interface
      of the host machine is connected to.
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    </p>
3241 3242 3243 3244 3245 3246 3247
    <p>
      The interface can have additional parameters as shown below,
      if the switch is conforming to the IEEE 802.1Qbg standard.
      The parameters of the virtualport element are documented in more detail
      in the IEEE 802.1Qbg standard. The values are network specific and
      should be provided by the network administrator. In 802.1Qbg terms,
      the Virtual Station Interface (VSI) represents the virtual interface
3248
      of a virtual machine. <span class="since">Since 0.8.2</span>
3249
    </p>
3250 3251 3252 3253
    <p>
      Please note that IEEE 802.1Qbg requires a non-zero value for the
      VLAN ID.
    </p>
3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278
    <dl>
      <dt><code>managerid</code></dt>
      <dd>The VSI Manager ID identifies the database containing the VSI type
        and instance definitions. This is an integer value and the
        value 0 is reserved.</dd>
      <dt><code>typeid</code></dt>
      <dd>The VSI Type ID identifies a VSI type characterizing the network
        access. VSI types are typically managed by network administrator.
        This is an integer value.
      </dd>
      <dt><code>typeidversion</code></dt>
      <dd>The VSI Type Version allows multiple versions of a VSI Type.
        This is an integer value.
      </dd>
      <dt><code>instanceid</code></dt>
      <dd>The VSI Instance ID Identifier is generated when a VSI instance
        (i.e. a virtual interface of a virtual machine) is created.
        This is a globally unique identifier.
      </dd>
    </dl>
<pre>
  ...
  &lt;devices&gt;
    ...
    &lt;interface type='direct'&gt;
3279
      &lt;source dev='eth0.2' mode='vepa'/&gt;
3280 3281 3282 3283 3284 3285
      &lt;virtualport type="802.1Qbg"&gt;
        &lt;parameters managerid="11" typeid="1193047" typeidversion="2" instanceid="09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f"/&gt;
      &lt;/virtualport&gt;
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>
3286

3287 3288 3289 3290 3291 3292 3293 3294 3295
    <p>
      The interface can have additional parameters as shown below
      if the switch is conforming to the IEEE 802.1Qbh standard.
      The values are network specific and should be provided by the
      network administrator. <span class="since">Since 0.8.2</span>
    </p>
    <dl>
      <dt><code>profileid</code></dt>
      <dd>The profile ID contains the name of the port profile that is to
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        be applied to this interface.  This name is resolved by the port
3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314
        profile database into the network parameters from the port profile,
        and those network parameters will be applied to this interface.
      </dd>
    </dl>
  <pre>
  ...
  &lt;devices&gt;
    ...
    &lt;interface type='direct'&gt;
      &lt;source dev='eth0' mode='private'/&gt;
      &lt;virtualport type='802.1Qbh'&gt;
        &lt;parameters profileid='finance'/&gt;
      &lt;/virtualport&gt;
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...
  </pre>

3315 3316 3317 3318 3319 3320 3321 3322

    <h5><a name="elementsNICSHostdev">PCI Passthrough</a></h5>

    <p>
      A PCI network device (specified by the &lt;source&gt; element)
      is directly assigned to the guest using generic device
      passthrough, after first optionally setting the device's MAC
      address to the configured value, and associating the device with
3323
      an 802.1Qbh capable switch using an optionally specified
3324
      &lt;virtualport&gt; element (see the examples of virtualport
3325 3326 3327 3328 3329 3330 3331 3332 3333
      given above for type='direct' network devices). Note that - due
      to limitations in standard single-port PCI ethernet card driver
      design - only SR-IOV (Single Root I/O Virtualization) virtual
      function (VF) devices can be assigned in this manner; to assign
      a standard single-port PCI or PCIe ethernet card to a guest, use
      the traditional &lt;hostdev&gt; device definition and
      <span class="since">Since 0.9.11</span>
    </p>

3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345
    <p>
      To use VFIO device assignment rather than traditional/legacy KVM
      device assignment (VFIO is a new method of device assignment
      that is compatible with UEFI Secure Boot), a type='hostdev'
      interface can have an optional <code>driver</code> sub-element
      with a <code>name</code> attribute set to "vfio". To use legacy
      KVM device assignment you can set <code>name</code> to "kvm" (or
      simply omit the <code>&lt;driver&gt;</code> element, since "kvm"
      is currently the default).
      <span class="since">Since 1.0.5 (QEMU and KVM only, requires kernel 3.6 or newer)</span>
    </p>

3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363
    <p>
      Note that this "intelligent passthrough" of network devices is
      very similar to the functionality of a standard &lt;hostdev&gt;
      device, the difference being that this method allows specifying
      a MAC address and &lt;virtualport&gt; for the passed-through
      device. If these capabilities are not required, if you have a
      standard single-port PCI, PCIe, or USB network card that doesn't
      support SR-IOV (and hence would anyway lose the configured MAC
      address during reset after being assigned to the guest domain),
      or if you are using a version of libvirt older than 0.9.11, you
      should use standard &lt;hostdev&gt; to assign the device to the
      guest instead of &lt;interface type='hostdev'/&gt;.
    </p>

<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='hostdev'&gt;
3364
      &lt;driver name='vfio'/&gt;
3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376
      &lt;source&gt;
        &lt;address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/&gt;
      &lt;/source&gt;
      &lt;mac address='52:54:00:6d:90:02'&gt;
      &lt;virtualport type='802.1Qbh'&gt;
        &lt;parameters profileid='finance'/&gt;
      &lt;/virtualport&gt;
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>


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    <h5><a name="elementsNICSMulticast">Multicast tunnel</a></h5>

    <p>
      A multicast group is setup to represent a virtual network. Any VMs
      whose network devices are in the same multicast group can talk to each
      other even across hosts. This mode is also available to unprivileged
      users. There is no default DNS or DHCP support and no outgoing network
      access. To provide outgoing network access, one of the VMs should have a
      2nd NIC which is connected to one of the first 4 network types and do the
      appropriate routing. The multicast protocol is compatible with that used
      by user mode linux guests too. The source address used must be from the
      multicast address block.
    </p>

3391 3392 3393 3394
<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='mcast'&gt;
3395
      &lt;mac address='52:54:00:6d:90:01'&gt;
3396 3397 3398 3399
      &lt;source address='230.0.0.1' port='5558'/&gt;
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>
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3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411

    <h5><a name="elementsNICSTCP">TCP tunnel</a></h5>

    <p>
      A TCP client/server architecture provides a virtual network. One VM
      provides the server end of the network, all other VMS are configured as
      clients. All network traffic is routed between the VMs via the server.
      This mode is also available to unprivileged users. There is no default
      DNS or DHCP support and no outgoing network access. To provide outgoing
      network access, one of the VMs should have a 2nd NIC which is connected
      to one of the first 4 network types and do the appropriate routing.</p>

3412 3413 3414 3415
<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='server'&gt;
3416
      &lt;mac address='52:54:00:22:c9:42'&gt;
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3417
      &lt;source address='192.168.0.1' port='5558'/&gt;
3418 3419 3420
    &lt;/interface&gt;
    ...
    &lt;interface type='client'&gt;
3421 3422
      &lt;mac address='52:54:00:8b:c9:51'&gt;
      &lt;source address='192.168.0.1' port='5558'/&gt;
3423 3424 3425
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>
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3427 3428
    <h5><a name="elementsNICSModel">Setting the NIC model</a></h5>

3429 3430 3431 3432 3433 3434 3435 3436 3437 3438
<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='network'&gt;
      &lt;source network='default'/&gt;
      &lt;target dev='vnet1'/&gt;
      <b>&lt;model type='ne2k_pci'/&gt;</b>
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>
3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460

    <p>
      For hypervisors which support this, you can set the model of
      emulated network interface card.
    </p>

    <p>
      The values for <code>type</code> aren't defined specifically by
      libvirt, but by what the underlying hypervisor supports (if
      any).  For QEMU and KVM you can get a list of supported models
      with these commands:
    </p>

<pre>
qemu -net nic,model=? /dev/null
qemu-kvm -net nic,model=? /dev/null
</pre>

    <p>
      Typical values for QEMU and KVM include:
      ne2k_isa i82551 i82557b i82559er ne2k_pci pcnet rtl8139 e1000 virtio
    </p>
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3462 3463 3464 3465 3466 3467 3468 3469 3470
    <h5><a name="elementsDriverBackendOptions">Setting NIC driver-specific options</a></h5>

<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='network'&gt;
      &lt;source network='default'/&gt;
      &lt;target dev='vnet1'/&gt;
      &lt;model type='virtio'/&gt;
3471
      <b>&lt;driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off' queues='5'/&gt;</b>
3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>

    <p>
      Some NICs may have tunable driver-specific options. These are
      set as attributes of the <code>driver</code> sub-element of the
      interface definition. Currently the following attributes are
      available for the <code>"virtio"</code> NIC driver:
    </p>

    <dl>
3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495
      <dt><code>name</code></dt>
      <dd>
        The optional <code>name</code> attribute forces which type of
        backend driver to use. The value can be either 'qemu' (a
        user-space backend) or 'vhost' (a kernel backend, which
        requires the vhost module to be provided by the kernel); an
        attempt to require the vhost driver without kernel support
        will be rejected.  If this attribute is not present, then the
        domain defaults to 'vhost' if present, but silently falls back
        to 'qemu' without error.
        <span class="since">Since 0.8.8 (QEMU and KVM only)</span>
      </dd>
3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508
      <dd>
        For interfaces of type='hostdev' (PCI passthrough devices)
        the <code>name</code> attribute can optionally be set to
        "vfio" or "kvm". "vfio" tells libvirt to use VFIO device
        assignment rather than traditional KVM device assignment (VFIO
        is a new method of device assignment that is compatible with
        UEFI Secure Boot), and "kvm" tells libvirt to use the legacy
        device assignment performed directly by the kvm kernel module
        (the default is currently "kvm", but is subject to change).
        <span class="since">Since 1.0.5 (QEMU and KVM only, requires
        kernel 3.6 or newer)</span>
      </dd>

3509 3510 3511 3512 3513
      <dt><code>txmode</code></dt>
      <dd>
        The <code>txmode</code> attribute specifies how to handle
        transmission of packets when the transmit buffer is full. The
        value can be either 'iothread' or 'timer'.
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        <span class="since">Since 0.8.8 (QEMU and KVM only)</span><br/><br/>
3515 3516 3517 3518

        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
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3519
        option).<br/><br/>
3520 3521 3522 3523

        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
E
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3524
        fires, another attempt is made to send more data.<br/><br/>
3525 3526 3527 3528 3529

        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
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        cpu where the guest generated the packets."<br/><br/>
3531

3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547
        <b>In general you should leave this option alone, unless you
        are very certain you know what you are doing.</b>
      </dd>
      <dt><code>ioeventfd</code></dt>
      <dd>
        This optional attribute allows users to set
        <a href='https://patchwork.kernel.org/patch/43390/'>
        domain I/O asynchronous handling</a> for interface device.
        The default is left to the discretion of the hypervisor.
        Accepted values are "on" and "off". Enabling this allows
        qemu to execute VM while a separate thread handles I/O.
        Typically guests experiencing high system CPU utilization
        during I/O will benefit from this. On the other hand,
        on overloaded host it could increase guest I/O latency.
        <span class="since">Since 0.9.3 (QEMU and KVM only)</span><br/><br/>

3548
        <b>In general you should leave this option alone, unless you
3549 3550 3551 3552 3553 3554
        are very certain you know what you are doing.</b>
      </dd>
      <dt><code>event_idx</code></dt>
      <dd>
        The <code>event_idx</code> attribute controls some aspects of
        device event processing. The value can be either 'on' or 'off'
3555
        - if it is on, it will reduce the number of interrupts and
3556 3557 3558 3559 3560 3561 3562
        exits for the guest. The default is determined by QEMU;
        usually if the feature is supported, default is on. In case
        there is a situation where this behavior is suboptimal, this
        attribute provides a way to force the feature off.
        <span class="since">Since 0.9.5 (QEMU and KVM only)</span><br/><br/>

        <b>In general you should leave this option alone, unless you
3563 3564
        are very certain you know what you are doing.</b>
      </dd>
3565 3566 3567 3568 3569 3570 3571 3572 3573 3574
      <dt><code>queues</code></dt>
      <dd>
        The optional <code>queues</code> attribute controls the number of
        queues to be used for the<a href="http://www.linux-kvm.org/page/Multiqueue">
        Multiqueue virtio-net</a> feature. If the interface has <code>&lt;model
        type='virtio'/&gt;</code>, multiple packet processing queues can be
        created; each queue will potentially be handled by a different
        processor, resulting in much higher throughput.
        <span class="since">Since 1.0.6 (QEMU and KVM only)</span>
      </dd>
3575 3576
    </dl>

3577 3578
    <h5><a name="elementsNICSTargetOverride">Overriding the target element</a></h5>

3579 3580 3581 3582 3583 3584 3585 3586 3587
<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='network'&gt;
      &lt;source network='default'/&gt;
      <b>&lt;target dev='vnet1'/&gt;</b>
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>
3588 3589

    <p>
E
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      If no target is specified, certain hypervisors will
      automatically generate a name for the created tun device. This
3592
      name can be manually specified, however the name <i>must not
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3593 3594 3595
      start with either 'vnet' or 'vif'</i>, which are prefixes
      reserved by libvirt and certain hypervisors. Manually specified
      targets using these prefixes will be ignored.
3596 3597
    </p>

3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611
    <h5><a name="elementsNICSBoot">Specifying boot order</a></h5>

<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='network'&gt;
      &lt;source network='default'/&gt;
      &lt;target dev='vnet1'/&gt;
      <b>&lt;boot order='1'/&gt;</b>
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>

    <p>
3612
      For hypervisors which support this, you can set a specific NIC to
3613 3614 3615 3616 3617 3618 3619 3620
      be used for network boot. The <code>order</code> attribute determines
      the order in which devices will be tried during boot sequence. The
      per-device <code>boot</code> elements cannot be used together with
      general boot elements in
      <a href="#elementsOSBIOS">BIOS bootloader</a> section.
      <span class="since">Since 0.8.8</span>
    </p>

3621 3622 3623 3624 3625 3626 3627 3628
    <h5><a name="elementsNICSROM">Interface ROM BIOS configuration</a></h5>

<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='network'&gt;
      &lt;source network='default'/&gt;
      &lt;target dev='vnet1'/&gt;
3629
      <b>&lt;rom bar='on' file='/etc/fake/boot.bin'/&gt;</b>
3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642
    &lt;/interface&gt;
  &lt;/devices&gt;
  ...</pre>

    <p>
      For hypervisors which support this, you can change how a PCI Network
      device's ROM is presented to the guest. The <code>bar</code>
      attribute can be set to "on" or "off", and determines whether
      or not the device's ROM will be visible in the guest's memory
      map. (In PCI documentation, the "rombar" setting controls the
      presence of the Base Address Register for the ROM). If no rom
      bar is specified, the qemu default will be used (older
      versions of qemu used a default of "off", while newer qemus
3643 3644 3645 3646 3647 3648
      have a default of "on").
      The optional <code>file</code> attribute is used to point to a
      binary file to be presented to the guest as the device's ROM
      BIOS. This can be useful to provide an alternative boot ROM for a
      network device.
      <span class="since">Since 0.9.10 (QEMU and KVM only)</span>.
3649 3650
    </p>

3651 3652 3653 3654 3655 3656 3657 3658 3659
    <h5><a name="elementQoS">Quality of service</a></h5>

<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='network'&gt;
      &lt;source network='default'/&gt;
      &lt;target dev='vnet0'/&gt;
      <b>&lt;bandwidth&gt;
3660
        &lt;inbound average='1000' peak='5000' floor='200' burst='1024'/&gt;
3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674
        &lt;outbound average='128' peak='256' burst='256'/&gt;
      &lt;/bandwidth&gt;</b>
    &lt;/interface&gt;
  &lt;devices&gt;
  ...</pre>

    <p>
      This part of interface XML provides setting quality of service. Incoming
      and outgoing traffic can be shaped independently. The
      <code>bandwidth</code> element can have at most one <code>inbound</code>
      and at most one <code>outbound</code> child elements. Leaving any of these
      children element out result in no QoS applied on that traffic direction.
      So, when you want to shape only domain's incoming traffic, use
      <code>inbound</code> only, and vice versa. Each of these elements have one
3675 3676 3677
      mandatory attribute <code>average</code> (or <code>floor</code> as
      described below). <code>average</code> specifies average bit rate on
      the interface being shaped. Then there are two optional attributes:
3678 3679 3680 3681 3682
      <code>peak</code>, which specifies maximum rate at which interface can send
      data, and <code>burst</code>, amount of bytes that can be burst at
      <code>peak</code> speed. Accepted values for attributes are integer
      numbers. The units for <code>average</code> and <code>peak</code> attributes
      are kilobytes per second, and for the <code>burst</code> just kilobytes.
3683 3684 3685
      Note the limitation of implementation: the <code>peak</code> attribute in
      <code>outbound</code> element is ignored (as linux ingress filters don't
      know it yet). <span class="since">Since 0.9.4</span> The <code>inbound</code> can
3686 3687 3688 3689 3690 3691 3692 3693
      optionally have <code>floor</code> attribute. This is there for
      guaranteeing minimal throughput for shaped interfaces. This, however,
      requires that all traffic goes through one point where QoS decisions can
      take place. That's why this attribute works only for virtual networks for
      now (that is <code>&lt;interface type='network'/&gt;</code> with a
      forward type of route, nat, or no forward at all). Moreover, the
      virtual network the interface is connected to is required to have at least
      inbound QoS set (<code>average</code> at least). Moreover, with
3694
      <code>floor</code> attribute users don't need to specify
3695 3696 3697 3698
      <code>average</code>. However, <code>peak</code> and <code>burst</code>
      attributes still require <code>average</code>. Currently, linux kernel
      doesn't allow ingress qdiscs to have any classes therefore
      <code>floor</code> can be applied only on <code>inbound</code> and not
3699
      <code>outbound</code>. <span class="since">Since 1.0.1</span>
3700 3701
    </p>

3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715
    <h5><a name="elementVlanTag">Setting VLAN tag (on supported network types only)</a></h5>

<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='bridge'&gt;
      <b>&lt;vlan&gt;</b>
        <b>&lt;tag id='42'/&gt;</b>
      <b>&lt;/vlan&gt;</b>
      &lt;source bridge='ovsbr0'/&gt;
      &lt;virtualport type='openvswitch'&gt;
        &lt;parameters interfaceid='09b11c53-8b5c-4eeb-8f00-d84eaa0aaa4f'/&gt;
      &lt;/virtualport&gt;
    &lt;/interface&gt;
3716 3717 3718 3719 3720 3721 3722
    &lt;interface type='bridge'&gt;
      <b>&lt;vlan trunk='yes'&gt;</b>
        <b>&lt;tag id='42'/&gt;</b>
        <b>&lt;tag id='123' nativeMode='untagged'/&gt;</b>
      <b>&lt;/vlan&gt;</b>
      ...
    &lt;/interface&gt;
3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738
  &lt;devices&gt;
  ...</pre>

    <p>
      If (and only if) the network connection used by the guest
      supports vlan tagging transparent to the guest, an
      optional <code>&lt;vlan&gt;</code> element can specify one or
      more vlan tags to apply to the guest's network
      traffic <span class="since">Since 0.10.0</span>. (openvswitch
      and type='hostdev' SR-IOV interfaces do support transparent vlan
      tagging of guest traffic; everything else, including standard
      linux bridges and libvirt's own virtual networks, <b>do not</b>
      support it. 802.1Qbh (vn-link) and 802.1Qbg (VEPA) switches
      provide their own way (outside of libvirt) to tag guest traffic
      onto specific vlans.) To allow for specification of multiple
      tags (in the case of vlan trunking), a
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      subelement, <code>&lt;tag&gt;</code>, specifies which vlan tag
3740 3741 3742 3743 3744 3745 3746 3747 3748
      to use (for example: <code>&lt;tag id='42'/&gt;</code>. If an
      interface has more than one <code>&lt;vlan&gt;</code> element
      defined, it is assumed that the user wants to do VLAN trunking
      using all the specified tags. In the case that vlan trunking
      with a single tag is desired, the optional
      attribute <code>trunk='yes'</code> can be added to the toplevel
      vlan element.
    </p>

3749 3750 3751
    <p>
      For network connections using openvswitch it is possible to
      configure the 'native-tagged' and 'native-untagged' vlan modes
3752
      <span class="since">Since 1.1.0.</span> This uses the optional
3753 3754 3755 3756 3757
      <code>nativeMode</code> attribute on the <code>&lt;tag&gt;</code>
      element: <code>nativeMode</code> may be set to 'tagged' or
      'untagged'. The id atribute of the element sets the native vlan.
    </p>

3758
    <h5><a name="elementLink">Modifying virtual link state</a></h5>
3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778
<pre>
  ...
  &lt;devices&gt;
    &lt;interface type='network'&gt;
      &lt;source network='default'/&gt;
      &lt;target dev='vnet0'/&gt;
      <b>&lt;link state='down'/&gt;</b>
    &lt;/interface&gt;
  &lt;devices&gt;
  ...</pre>

    <p>
      This element provides means of setting state of the virtual network link.
      Possible values for attribute <code>state</code> are <code>up</code> and
      <code>down</code>. If <code>down</code> is specified as the value, the interface
      behaves as if it had the network cable disconnected. Default behavior if this
      element is unspecified is to have the link state <code>up</code>.
      <span class="since">Since 0.9.5</span>
    </p>

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    <h4><a name="elementsInput">Input devices</a></h4>

    <p>
E
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3782 3783 3784 3785
      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,
D
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3786 3787 3788
      to provide a graphics tablet for absolute cursor movement.
    </p>

3789 3790 3791 3792 3793 3794
<pre>
  ...
  &lt;devices&gt;
    &lt;input type='mouse' bus='usb'/&gt;
  &lt;/devices&gt;
  ...</pre>
D
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3795 3796 3797

    <dl>
      <dt><code>input</code></dt>
E
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3798 3799 3800
      <dd>The <code>input</code> element has one mandatory attribute,
        the <code>type</code> whose value can be either 'mouse' or
        'tablet'. The latter provides absolute
M
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        cursor movement, while the former uses relative movement. The optional
        <code>bus</code> attribute can be used to refine the exact device type.
        It takes values "xen" (paravirtualized), "ps2" and "usb".</dd>
D
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3804 3805
    </dl>

E
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3806 3807 3808
    <p>
      The <code>input</code> element has an optional
      sub-element <code>&lt;address&gt;</code> which can tie the
3809 3810
      device to a particular PCI
      slot, <a href="#elementsAddress">documented above</a>.
E
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3811
    </p>
D
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3812

M
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3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835
    <h4><a name="elementsHub">Hub devices</a></h4>

    <p>
      A hub is a device that expands a single port into several so
      that there are more ports available to connect devices to a host
      system.
    </p>

<pre>
  ...
  &lt;devices&gt;
    &lt;hub type='usb'/&gt;
  &lt;/devices&gt;
  ...</pre>

    <dl>
      <dt><code>hub</code></dt>
      <dd>The <code>hub</code> element has one mandatory attribute,
        the <code>type</code> whose value can only be 'usb'.</dd>
    </dl>

    <p>
      The <code>hub</code> element has an optional
3836 3837 3838 3839
      sub-element <code>&lt;address&gt;</code>
      with <code>type='usb'</code>which can tie the device to a
      particular controller, <a href="#elementsAddress">documented
      above</a>.
M
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    </p>

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    <h4><a name="elementsGraphics">Graphical framebuffers</a></h4>

    <p>
      A graphics device allows for graphical interaction with the
      guest OS. A guest will typically have either a framebuffer
      or a text console configured to allow interaction with the
      admin.
    </p>

3851 3852 3853 3854
<pre>
  ...
  &lt;devices&gt;
    &lt;graphics type='sdl' display=':0.0'/&gt;
3855
    &lt;graphics type='vnc' port='5904' sharePolicy='allow-exclusive'&gt;
3856 3857
      &lt;listen type='address' address='1.2.3.4'/&gt;
    &lt;/graphics&gt;
3858 3859
    &lt;graphics type='rdp' autoport='yes' multiUser='yes' /&gt;
    &lt;graphics type='desktop' fullscreen='yes'/&gt;
3860 3861 3862
    &lt;graphics type='spice'&gt;
      &lt;listen type='network' network='rednet'/&gt;
    &lt;/graphics&gt;
3863 3864
  &lt;/devices&gt;
  ...</pre>
D
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    <dl>
      <dt><code>graphics</code></dt>
      <dd>The <code>graphics</code> element has a mandatory <code>type</code>
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        attribute which takes the value "sdl", "vnc", "rdp" or "desktop":
3870 3871 3872
        <dl>
          <dt><code>"sdl"</code></dt>
          <dd>
E
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            This displays a window on the host desktop, it can take 3
            optional arguments: a <code>display</code> attribute for
            the display to use, an <code>xauth</code> attribute for
            the authentication identifier, and an
            optional <code>fullscreen</code> attribute accepting
            values 'yes' or 'no'.
3879 3880 3881
          </dd>
          <dt><code>"vnc"</code></dt>
          <dd>
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            Starts a VNC server. The <code>port</code> attribute
            specifies the TCP port number (with -1 as legacy syntax
            indicating that it should be
            auto-allocated). The <code>autoport</code> attribute is
            the new preferred syntax for indicating autoallocation of
            the TCP port to use.  The <code>listen</code> attribute is
            an IP address for the server to listen
            on. The <code>passwd</code> attribute provides a VNC
            password in clear text. The <code>keymap</code> attribute
            specifies the keymap to use. It is possible to set a limit
            on the validity of the password be giving an
            timestamp <code>passwdValidTo='2010-04-09T15:51:00'</code>
3894 3895 3896 3897
            assumed to be in UTC. The <code>connected</code> attribute
            allows control of connected client during password changes.
            VNC accepts <code>keep</code> value only.
            <span class="since">since 0.9.3</span>
3898 3899 3900 3901 3902 3903 3904 3905 3906 3907
            NB, this may not be supported by all hypervisors.<br/>
            The optional <code>sharePolicy</code> attribute specifies vnc server
            display sharing policy. "allow-exclusive" allows clients to ask
            for exclusive access by dropping other connections. Connecting
            multiple clients in parallel requires all clients asking for a
            shared session (vncviewer: -Shared switch). This is the default
            value. "force-shared" disables exclusive client access, every
            connection has to specify -Shared switch for vncviewer. "ignore"
            welcomes every connection unconditionally
            <span class="since">since 1.0.6</span>. <br/> <br/>
3908 3909 3910
            Rather than using listen/port, QEMU supports a
            <code>socket</code> attribute for listening on a unix
            domain socket path.<span class="since">Since 0.8.8</span>
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            For VNC WebSocket functionality, <code>websocket</code>
            attribute may be used to specify port to listen on (with
            -1 meaning auto-allocation and <code>autoport</code>
            having no effect due to security reasons).
            <span class="since">Since 1.0.6</span>
3917 3918 3919
          </dd>
          <dt><code>"spice"</code></dt>
          <dd>
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            <p>
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              Starts a SPICE server. The <code>port</code> attribute
              specifies the TCP port number (with -1 as legacy syntax
              indicating that it should be auto-allocated),
              while <code>tlsPort</code> gives an alternative secure
              port number. The <code>autoport</code> attribute is the
              new preferred syntax for indicating autoallocation of
3927
              needed port numbers.  The <code>listen</code> attribute is
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              an IP address for the server to listen
              on. The <code>passwd</code> attribute provides a SPICE
              password in clear text. The <code>keymap</code>
              attribute specifies the keymap to use. It is possible to
              set a limit on the validity of the password be giving an
              timestamp <code>passwdValidTo='2010-04-09T15:51:00'</code>
3934 3935 3936 3937 3938 3939 3940 3941
              assumed to be in UTC. The <code>connected</code> attribute
              allows control of connected client during password changes.
              SPICE accepts <code>keep</code> to keep client connected,
              <code>disconnect</code> to disconnect client and
              <code>fail</code> to fail changing password.
              <span class="since">Since 0.9.3</span>
              NB, this may not be supported by all hypervisors.
              <span class="since">"spice" since 0.8.6</span>.
3942 3943 3944 3945 3946 3947 3948
              The <code>defaultMode</code> attribute sets the default channel
              security policy, valid values are <code>secure</code>,
              <code>insecure</code> and the default <code>any</code>
              (which is secure if possible, but falls back to insecure
              rather than erroring out if no secure path is
              available). <span class="since">"defaultMode" since
              0.9.12</span>.
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            </p>
            <p>
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              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 &lt;channel&gt; elements inside the
              main &lt;graphics&gt; element. Valid channel names
              include <code>main</code>, <code>display</code>,
              <code>inputs</code>, <code>cursor</code>,
3958 3959 3960 3961 3962
              <code>playback</code>, <code>record</code>
              (all <span class="since"> since 0.8.6</span>);
              <code>smartcard</code> (<span class="since">since
              0.8.8</span>); and <code>usbredir</code>
              (<span class="since">since 0.9.12</span>).
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            </p>
            <pre>
3965 3966 3967
  &lt;graphics type='spice' port='-1' tlsPort='-1' autoport='yes'&gt;
    &lt;channel name='main' mode='secure'/&gt;
    &lt;channel name='record' mode='insecure'/&gt;
3968
    &lt;image compression='auto_glz'/&gt;
3969
    &lt;streaming mode='filter'/&gt;
3970
    &lt;clipboard copypaste='no'/&gt;
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    &lt;mouse mode='client'/&gt;
3972
  &lt;/graphics&gt;</pre>
3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989
            <p>
              Spice supports variable compression settings for audio,
              images and streaming, <span class="since">since
              0.9.1</span>.  These settings are accessible via
              the <code>compression</code> attribute in all following
              elements: <code>image</code> to set image compression
              (accepts <code>auto_glz</code>, <code>auto_lz</code>,
              <code>quic</code>, <code>glz</code>, <code>lz</code>,
              <code>off</code>), <code>jpeg</code> for JPEG
              compression for images over wan
              (accepts <code>auto</code>, <code>never</code>,
              <code>always</code>), <code>zlib</code> for configuring
              wan image compression (accepts <code>auto</code>,
              <code>never</code>, <code>always</code>)
              and <code>playback</code> for enabling audio stream
              compression (accepts <code>on</code> or <code>off</code>).
            </p>
3990 3991
            <p>
              Streaming mode is set by the <code>streaming</code>
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              element, settings its <code>mode</code> attribute to one
3993 3994 3995
              of <code>filter</code>, <code>all</code>
              or <code>off</code>, <span class="since">since 0.9.2</span>.
            </p>
3996 3997 3998 3999 4000 4001 4002
            <p>
              Copy &amp; Paste functionality (via Spice agent) is set
              by the <code>clipboard</code> element. It is enabled by
              default, and can be disabled by setting
              the <code>copypaste</code> property
              to <code>no</code>, <span class="since">since
              0.9.3</span>.
4003
            </p>
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            <p>
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              Mouse mode is set by the <code>mouse</code> element,
              setting its <code>mode</code> attribute to one of
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              <code>server</code> or <code>client</code> ,
              <span class="since">since 0.9.11</span>. If no mode is
              specified, the qemu default will be used (client mode).
            </p>
4011 4012 4013
          </dd>
          <dt><code>"rdp"</code></dt>
          <dd>
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            Starts a RDP server. The <code>port</code> attribute
            specifies the TCP port number (with -1 as legacy syntax
            indicating that it should be
            auto-allocated). The <code>autoport</code> attribute is
            the new preferred syntax for indicating autoallocation of
            the TCP port to use. The <code>replaceUser</code>
            attribute is a boolean deciding whether multiple
            simultaneous connections to the VM are permitted.
4022 4023 4024 4025
            The <code>multiUser</code> attribute is a boolean deciding
            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.
4026 4027 4028
          </dd>
          <dt><code>"desktop"</code></dt>
          <dd>
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            This value is reserved for VirtualBox domains for the
            moment. It displays a window on the host desktop,
            similarly to "sdl", but using the VirtualBox viewer. Just
            like "sdl", it accepts the optional
            attributes <code>display</code>
            and <code>fullscreen</code>.
4035 4036 4037 4038 4039
          </dd>
        </dl>
      </dd>
    </dl>

4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087
    <p>
      Rather than putting the address information used to set up the
      listening socket for graphics types <code>vnc</code>
      and <code>spice</code> in
      the <code>&lt;graphics&gt;</code> <code>listen</code> attribute,
      a separate subelement of <code>&lt;graphics&gt;</code>,
      called <code>&lt;listen&gt;</code> can be specified (see the
      examples above)<span class="since">since
      0.9.4</span>. <code>&lt;listen&gt;</code> accepts the following
      attributes:
    </p>
    <dl>
      <dt><code>type</code></dt>
      <dd>Set to either <code>address</code>
        or <code>network</code>. This tells whether this listen
        element is specifying the address to be used directly, or by
        naming a network (which will then be used to determine an
        appropriate address for listening).
      </dd>
    </dl>
    <dl>
      <dt><code>address</code></dt>
      <dd>if <code>type='address'</code>, the <code>address</code>
        attribute will contain either an IP address or hostname (which
        will be resolved to an IP address via a DNS query) to listen
        on. In the "live" XML of a running domain, this attribute will
        be set to the IP address used for listening, even
        if <code>type='network'</code>.
      </dd>
    </dl>
    <dl>
      <dt><code>network</code></dt>
      <dd>if <code>type='network'</code>, the <code>network</code>
        attribute will contain the name of a network in libvirt's list
        of configured networks. The named network configuration will
        be examined to determine an appropriate listen address. For
        example, if the network has an IPv4 address in its
        configuration (e.g. if it has a forward type
        of <code>route</code>, <code>nat</code>, or no forward type
        (isolated)), the first IPv4 address listed in the network's
        configuration will be used. If the network is describing a
        host bridge, the first IPv4 address associated with that
        bridge device will be used, and if the network is describing
        one of the 'direct' (macvtap) modes, the first IPv4 address of
        the first forward dev will be used.
      </dd>
    </dl>

4088 4089 4090 4091 4092
    <h4><a name="elementsVideo">Video devices</a></h4>
    <p>
      A video device.
    </p>

4093 4094 4095 4096 4097
<pre>
  ...
  &lt;devices&gt;
    &lt;video&gt;
      &lt;model type='vga' vram='8192' heads='1'&gt;
4098
        &lt;acceleration accel3d='yes' accel2d='yes'/&gt;
4099 4100 4101 4102
      &lt;/model&gt;
    &lt;/video&gt;
  &lt;/devices&gt;
  ...</pre>
4103 4104 4105

    <dl>
      <dt><code>video</code></dt>
4106
      <dd>
4107 4108
        The <code>video</code> element is the container for describing
        video devices. For backwards compatibility, if no <code>video</code>
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        is set but there is a <code>graphics</code> in domain xml, then libvirt
        will add a default <code>video</code> according to the guest type.
        For a guest of type "kvm", the default <code>video</code> for it is:
        <code>type</code> with value "cirrus", <code>vram</code> with value
4113 4114 4115 4116
        "9216", and <code>heads</code> with value "1". By default, the first
        video device in domain xml is the primary one, but the optional
        attribute <code>primary</code> (<span class="since">since 1.0.2</span>)
        with value 'yes' can be used to mark the primary in cases of mutiple
4117 4118 4119 4120
        video device. The non-primary must be type of "qxl". The optional
        attribute <code>ram</code> (<span class="since">since
        1.0.2</span>) is allowed for "qxl" type only and specifies
        the size of the primary bar, while <code>vram</code> specifies the
4121 4122
        secondary bar size.  If "ram" or "vram" are not supplied a default
        value is used.
4123
      </dd>
4124

4125 4126 4127
      <dt><code>model</code></dt>
      <dd>
        The <code>model</code> element has a mandatory <code>type</code>
4128 4129 4130
        attribute which takes the value "vga", "cirrus", "vmvga", "xen",
        "vbox", or "qxl" (<span class="since">since 0.8.6</span>)
        depending on the hypervisor features available.
4131 4132
        You can also provide the amount of video memory in kibibytes
        (blocks of 1024 bytes) using
4133 4134 4135 4136 4137 4138 4139 4140 4141
        <code>vram</code> and the number of screen with <code>heads</code>.
      </dd>

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

4150
    <h4><a name="elementsConsole">Consoles, serial, parallel &amp; channel devices</a></h4>
D
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    <p>
      A character device provides a way to interact with the virtual machine.
4154 4155
      Paravirtualized consoles, serial ports, parallel ports and channels are
      all classed as character devices and so represented using the same syntax.
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    </p>

4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178
<pre>
  ...
  &lt;devices&gt;
    &lt;parallel type='pty'&gt;
      &lt;source path='/dev/pts/2'/&gt;
      &lt;target port='0'/&gt;
    &lt;/parallel&gt;
    &lt;serial type='pty'&gt;
      &lt;source path='/dev/pts/3'/&gt;
      &lt;target port='0'/&gt;
    &lt;/serial&gt;
    &lt;console type='pty'&gt;
      &lt;source path='/dev/pts/4'/&gt;
      &lt;target port='0'/&gt;
    &lt;/console&gt;
    &lt;channel type='unix'&gt;
      &lt;source mode='bind' path='/tmp/guestfwd'/&gt;
      &lt;target type='guestfwd' address='10.0.2.1' port='4600'/&gt;
    &lt;/channel&gt;
  &lt;/devices&gt;
  ...</pre>
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4180 4181 4182 4183 4184
    <p>
      In each of these directives, the top-level element name (parallel, serial,
      console, channel) describes how the device is presented to the guest. The
      guest interface is configured by the <code>target</code> element.
    </p>
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4186 4187 4188 4189 4190 4191
    <p>
      The interface presented to the host is given in the <code>type</code>
      attribute of the top-level element. The host interface is
      configured by the <code>source</code> element.
    </p>

4192 4193 4194 4195 4196 4197 4198 4199
    <p>
      The <code>source</code> element may contain an optional
      <code>seclabel</code> to override the way that labelling
      is done on the socket path.  If this element is not present,
      the <a href="#seclabel">security label is inherited from
        the per-domain setting</a>.
    </p>

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    <p>
      Each character device element has an optional
      sub-element <code>&lt;address&gt;</code> which can tie the
      device to a
      particular <a href="#elementsControllers">controller</a> or PCI
      slot.
    </p>

4208 4209 4210 4211 4212 4213 4214 4215 4216
    <h5><a name="elementsCharGuestInterface">Guest interface</a></h5>

    <p>
      A character device presents itself to the guest as one of the following
      types.
    </p>

    <h6><a name="elementCharParallel">Parallel port</a></h6>

4217 4218 4219 4220 4221 4222 4223 4224 4225
<pre>
  ...
  &lt;devices&gt;
    &lt;parallel type='pty'&gt;
      &lt;source path='/dev/pts/2'/&gt;
      &lt;target port='0'/&gt;
    &lt;/parallel&gt;
  &lt;/devices&gt;
  ...</pre>
4226 4227 4228

    <p>
      <code>target</code> can have a <code>port</code> attribute, which
4229
      specifies the port number. Ports are numbered starting from 0. There are
4230 4231 4232 4233 4234
      usually 0, 1 or 2 parallel ports.
    </p>

    <h6><a name="elementCharSerial">Serial port</a></h6>

4235 4236 4237 4238 4239 4240 4241 4242 4243
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type='pty'&gt;
      &lt;source path='/dev/pts/3'/&gt;
      &lt;target port='0'/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
4244 4245 4246

    <p>
      <code>target</code> can have a <code>port</code> attribute, which
4247
      specifies the port number. Ports are numbered starting from 0. There are
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      usually 0, 1 or 2 serial ports. There is also an optional
      <code>type</code> attribute <span class="since">since 1.0.2</span>
4250
      which has two choices for its value, one is <code>isa-serial</code>,
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      the other is <code>usb-serial</code>. If <code>type</code> is missing,
      <code>isa-serial</code> will be used by default. For <code>usb-serial</code>
      an optional sub-element <code>&lt;address&gt;</code> with
      <code>type='usb'</code> can tie the device to a particular controller,
      <a href="#elementsAddress">documented above</a>.
4256 4257 4258 4259 4260
    </p>

    <h6><a name="elementCharConsole">Console</a></h6>

    <p>
4261 4262 4263 4264 4265 4266 4267
      The console element is used to represent interactive consoles. Depending
      on the type of guest in use, the consoles might be paravirtualized devices,
      or they might be a clone of a serial device, according to the following
      rules:
    </p>

    <ul>
4268
      <li>If no <code>targetType</code> attribute is set, then the default
4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281
        device type is according to the hypervisor's rules. The default
        type will be added when re-querying the XML fed into libvirt.
        For fully virtualized guests, the default device type will usually
        be a serial port.</li>
      <li>If the <code>targetType</code> attribute is <code>serial</code>,
        then if no <code>&lt;serial&gt;</code> element exists, the console
        element will be copied to the serial element. If a <code>&lt;serial&gt;</code>
        element does already exist, the console element will be ignored.</li>
      <li>If the <code>targetType</code> attribute is not <code>serial</code>,
        it will be treated normally.</li>
      <li>Only the first <code>console</code> element may use a <code>targetType</code>
        of <code>serial</code>. Secondary consoles must all be paravirtualized.
      </li>
4282 4283 4284 4285 4286 4287
      <li>On s390, the <code>console</code> element may use a
        <code>targetType</code> of <code>sclp</code> or <code>sclplm</code>
        (line mode). SCLP is the native console type for s390. There's no
        controller associated to SCLP consoles.
        <span class="since">Since 1.0.2</span>
      </li>
4288
    </ul>
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    <p>
      A virtio console device is exposed in the
      guest as /dev/hvc[0-7] (for more information, see
      <a href="http://fedoraproject.org/wiki/Features/VirtioSerial">http://fedoraproject.org/wiki/Features/VirtioSerial</a>)
      <span class="since">Since 0.8.3</span>
4295 4296
    </p>

4297 4298 4299 4300 4301 4302 4303
<pre>
  ...
  &lt;devices&gt;
    &lt;console type='pty'&gt;
      &lt;source path='/dev/pts/4'/&gt;
      &lt;target port='0'/&gt;
    &lt;/console&gt;
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    &lt;!-- KVM virtio console --&gt;
    &lt;console type='pty'&gt;
      &lt;source path='/dev/pts/5'/&gt;
      &lt;target type='virtio' port='0'/&gt;
    &lt;/console&gt;
4310 4311
  &lt;/devices&gt;
  ...</pre>
4312

4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323
<pre>
  ...
  &lt;devices&gt;
    &lt;!-- KVM s390 sclp console --&gt;
    &lt;console type='pty'&gt;
      &lt;source path='/dev/pts/1'/&gt;
      &lt;target type='sclp' port='0'/&gt;
    &lt;/console&gt;
  &lt;/devices&gt;
  ...</pre>

4324 4325 4326 4327 4328 4329
    <p>
      If the console is presented as a serial port, the <code>target</code>
      element has the same attributes as for a serial port. There is usually
      only 1 console.
    </p>

4330 4331 4332 4333 4334 4335 4336
    <h6><a name="elementCharChannel">Channel</a></h6>

    <p>
      This represents a private communication channel between the host and the
      guest.
    </p>

4337 4338 4339 4340 4341 4342 4343
<pre>
  ...
  &lt;devices&gt;
    &lt;channel type='unix'&gt;
      &lt;source mode='bind' path='/tmp/guestfwd'/&gt;
      &lt;target type='guestfwd' address='10.0.2.1' port='4600'/&gt;
    &lt;/channel&gt;
4344 4345 4346 4347 4348

    &lt;!-- KVM virtio channel --&gt;
    &lt;channel type='pty'&gt;
      &lt;target type='virtio' name='arbitrary.virtio.serial.port.name'/&gt;
    &lt;/channel&gt;
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    &lt;channel type='unix'&gt;
      &lt;source mode='bind' path='/var/lib/libvirt/qemu/f16x86_64.agent'/&gt;
      &lt;target type='virtio' name='org.qemu.guest_agent.0'/&gt;
    &lt;/channel&gt;
4353 4354 4355
    &lt;channel type='spicevmc'&gt;
      &lt;target type='virtio' name='com.redhat.spice.0'/&gt;
    &lt;/channel&gt;
4356 4357
  &lt;/devices&gt;
  ...</pre>
4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371

    <p>
      This can be implemented in a variety of ways. The specific type of
      channel is given in the <code>type</code> attribute of the
      <code>target</code> element. Different channel types have different
      <code>target</code> attributes.
    </p>

    <dl>
      <dt><code>guestfwd</code></dt>
      <dd>TCP traffic sent by the guest to a given IP address and port is
        forwarded to the channel device on the host. The <code>target</code>
        element must have <code>address</code> and <code>port</code> attributes.
        <span class="since">Since 0.7.3</span></dd>
4372 4373 4374

      <dt><code>virtio</code></dt>
      <dd>Paravirtualized virtio channel. Channel is exposed in the guest under
E
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        /dev/vport*, and if the optional element <code>name</code> is specified,
4376
        /dev/virtio-ports/$name (for more info, please see
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        <a href="http://fedoraproject.org/wiki/Features/VirtioSerial">http://fedoraproject.org/wiki/Features/VirtioSerial</a>). The
        optional element <code>address</code> can tie the channel to a
4379 4380
        particular <code>type='virtio-serial'</code>
        controller, <a href="#elementsAddress">documented above</a>.
D
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        With qemu, if <code>name</code> is "org.qemu.guest_agent.0",
        then libvirt can interact with a guest agent installed in the
        guest, for actions such as guest shutdown or file system quiescing.
        <span class="since">Since 0.7.7, guest agent interaction
4385
        since 0.9.10</span> Moreover, <span class="since">since 1.0.6</span>
4386 4387 4388 4389 4390
        it is possible to have source path auto generated for virtio unix channels.
        This is very useful in case of a qemu guest agent, where users don't
        usually care about the source path since it's libvirt who talks to
        the guest agent. In case users want to utilize this feature, they should
        leave <code>&lt;source&gt;</code> element out.
4391
      </dd>
4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404
      <dt><code>spicevmc</code></dt>
      <dd>Paravirtualized SPICE channel. The domain must also have a
        SPICE server as a <a href="#elementsGraphics">graphics
        device</a>, at which point the host piggy-backs messages
        across the <code>main</code> channel.  The <code>target</code>
        element must be present, with
        attribute <code>type='virtio'</code>; an optional
        attribute <code>name</code> controls how the guest will have
        access to the channel, and defaults
        to <code>name='com.redhat.spice.0'</code>.  The
        optional <code>address</code> element can tie the channel to a
        particular <code>type='virtio-serial'</code> controller.
        <span class="since">Since 0.8.8</span></dd>
4405 4406
    </dl>

4407 4408 4409 4410 4411 4412
    <h5><a name="elementsCharHostInterface">Host interface</a></h5>

    <p>
      A character device presents itself to the host as one of the following
      types.
    </p>
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4414
    <h6><a name="elementsCharSTDIO">Domain logfile</a></h6>
D
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4415 4416 4417 4418 4419 4420

    <p>
      This disables all input on the character device, and sends output
      into the virtual machine's logfile
    </p>

4421 4422 4423 4424
<pre>
  ...
  &lt;devices&gt;
    &lt;console type='stdio'&gt;
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4425
      &lt;target port='1'/&gt;
4426 4427 4428
    &lt;/console&gt;
  &lt;/devices&gt;
  ...</pre>
D
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4429 4430


4431
    <h6><a name="elementsCharFle">Device logfile</a></h6>
D
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4432 4433 4434 4435 4436 4437

    <p>
      A file is opened and all data sent to the character
      device is written to the file.
    </p>

4438 4439 4440 4441 4442 4443 4444 4445 4446
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type="file"&gt;
      &lt;source path="/var/log/vm/vm-serial.log"/&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
D
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4447

4448
    <h6><a name="elementsCharVC">Virtual console</a></h6>
D
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4449 4450 4451 4452 4453 4454 4455

    <p>
      Connects the character device to the graphical framebuffer in
      a virtual console. This is typically accessed via a special
      hotkey sequence such as "ctrl+alt+3"
    </p>

4456 4457 4458 4459 4460 4461 4462 4463
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type='vc'&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
D
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4464

4465
    <h6><a name="elementsCharNull">Null device</a></h6>
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4466 4467 4468 4469 4470 4471

    <p>
      Connects the character device to the void. No data is ever
      provided to the input. All data written is discarded.
    </p>

4472 4473 4474 4475 4476 4477 4478 4479
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type='null'&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
D
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4480

4481
    <h6><a name="elementsCharPTY">Pseudo TTY</a></h6>
D
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4482 4483 4484 4485 4486 4487 4488

    <p>
      A Pseudo TTY is allocated using /dev/ptmx. A suitable client
      such as 'virsh console' can connect to interact with the
      serial port locally.
    </p>

4489 4490 4491 4492 4493 4494 4495 4496 4497
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type="pty"&gt;
      &lt;source path="/dev/pts/3"/&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
D
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4498 4499 4500

    <p>
      NB special case if &lt;console type='pty'&gt;, then the TTY
A
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      path is also duplicated as an attribute tty='/dev/pts/3'
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4502 4503 4504 4505
      on the top level &lt;console&gt; tag. This provides compat
      with existing syntax for &lt;console&gt; tags.
    </p>

4506
    <h6><a name="elementsCharHost">Host device proxy</a></h6>
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4507 4508 4509 4510 4511

    <p>
      The character device is passed through to the underlying
      physical character device. The device types must match,
      eg the emulated serial port should only be connected to
A
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      a host serial port - don't connect a serial port to a parallel
D
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4513 4514 4515
      port.
    </p>

4516 4517 4518 4519 4520 4521
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type="dev"&gt;
      &lt;source path="/dev/ttyS0"/&gt;
      &lt;target port="1"/&gt;
E
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4522
    &lt;/serial&gt;
4523 4524
  &lt;/devices&gt;
  ...</pre>
D
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4525

4526
    <h6><a name="elementsCharPipe">Named pipe</a></h6>
4527 4528 4529 4530 4531 4532

    <p>
      The character device writes output to a named pipe. See pipe(7) for
      more info.
    </p>

4533 4534 4535 4536 4537 4538 4539 4540 4541
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type="pipe"&gt;
      &lt;source path="/tmp/mypipe"/&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
4542

4543
    <h6><a name="elementsCharTCP">TCP client/server</a></h6>
D
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4544 4545 4546

    <p>
      The character device acts as a TCP client connecting to a
4547
      remote server.
D
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4548 4549
    </p>

4550 4551 4552 4553 4554 4555 4556 4557 4558 4559
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type="tcp"&gt;
      &lt;source mode="connect" host="0.0.0.0" service="2445"/&gt;
      &lt;protocol type="raw"/&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
   ...</pre>
4560 4561 4562 4563 4564

    <p>
      Or as a TCP server waiting for a client connection.
    </p>

4565 4566 4567 4568 4569 4570 4571 4572 4573 4574
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type="tcp"&gt;
      &lt;source mode="bind" host="127.0.0.1" service="2445"/&gt;
      &lt;protocol type="raw"/&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
4575 4576

    <p>
E
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4577 4578 4579
      Alternatively you can use <code>telnet</code> instead
      of <code>raw</code> TCP.  <span class="since">Since 0.8.5</span>
      you can also use <code>telnets</code>
4580
      (secure telnet) and <code>tls</code>.
E
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4581
    </p>
4582

4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type="tcp"&gt;
      &lt;source mode="connect" host="0.0.0.0" service="2445"/&gt;
      &lt;protocol type="telnet"/&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
    ...
    &lt;serial type="tcp"&gt;
      &lt;source mode="bind" host="127.0.0.1" service="2445"/&gt;
      &lt;protocol type="telnet"/&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
D
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4599

4600
    <h6><a name="elementsCharUDP">UDP network console</a></h6>
D
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4601 4602 4603 4604 4605 4606

    <p>
      The character device acts as a UDP netconsole service,
      sending and receiving packets. This is a lossy service.
    </p>

4607 4608 4609 4610 4611 4612 4613 4614 4615 4616
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type="udp"&gt;
      &lt;source mode="bind" host="0.0.0.0" service="2445"/&gt;
      &lt;source mode="connect" host="0.0.0.0" service="2445"/&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
D
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4617

4618
    <h6><a name="elementsCharUNIX">UNIX domain socket client/server</a></h6>
D
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4619 4620 4621 4622 4623 4624

    <p>
      The character device acts as a UNIX domain socket server,
      accepting connections from local clients.
    </p>

4625 4626 4627 4628 4629 4630 4631 4632 4633
<pre>
  ...
  &lt;devices&gt;
    &lt;serial type="unix"&gt;
      &lt;source mode="bind" path="/tmp/foo"/&gt;
      &lt;target port="1"/&gt;
    &lt;/serial&gt;
  &lt;/devices&gt;
  ...</pre>
D
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4634

4635 4636 4637 4638 4639 4640 4641 4642

    <h4><a name="elementsSound">Sound devices</a></h4>

    <p>
      A virtual sound card can be attached to the host via the
      <code>sound</code> element. <span class="since">Since 0.4.3</span>
    </p>

4643 4644 4645 4646 4647 4648
<pre>
  ...
  &lt;devices&gt;
    &lt;sound model='es1370'/&gt;
  &lt;/devices&gt;
  ...</pre>
4649 4650 4651 4652 4653 4654 4655

    <dl>
      <dt><code>sound</code></dt>
      <dd>
        The <code>sound</code> element has one mandatory attribute,
        <code>model</code>, which specifies what real sound device is emulated.
        Valid values are specific to the underlying hypervisor, though typical
4656 4657 4658
        choices are 'es1370', 'sb16', 'ac97', and 'ich6'
        (<span class="since">
         'ac97' only since 0.6.0, 'ich6' only since 0.8.8</span>)
4659 4660 4661
      </dd>
    </dl>

4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680
    <p>
      <span class="since">Since 0.9.13</span>, a sound element
      with <code>ich6</code> model can have optional
      sub-elements <code>&lt;codec&gt;</code> to attach various audio
      codecs to the audio device. If not specified, a default codec
      will be attached to allow playback and recording. Valid values
      are 'duplex' (advertise a line-in and a line-out) and 'micro'
      (advertise a speaker and a microphone).
    </p>

<pre>
  ...
  &lt;devices&gt;
    &lt;sound model='ich6'&gt;
      &lt;codec type='micro'/&gt;
    &lt;sound/&gt;
  &lt;/devices&gt;
  ...</pre>

E
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4681 4682 4683
    <p>
      Each <code>sound</code> element has an optional
      sub-element <code>&lt;address&gt;</code> which can tie the
4684 4685
      device to a particular PCI
      slot, <a href="#elementsAddress">documented above</a>.
E
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4686 4687
    </p>

R
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4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707
    <h4><a name="elementsWatchdog">Watchdog device</a></h4>

    <p>
      A virtual hardware watchdog device can be added to the guest via
      the <code>watchdog</code> element.
      <span class="since">Since 0.7.3, QEMU and KVM only</span>
    </p>

    <p>
      The watchdog device requires an additional driver and management
      daemon in the guest.  Just enabling the watchdog in the libvirt
      configuration does not do anything useful on its own.
    </p>

    <p>
      Currently libvirt does not support notification when the
      watchdog fires.  This feature is planned for a future version of
      libvirt.
    </p>

4708 4709 4710 4711 4712 4713
<pre>
  ...
  &lt;devices&gt;
    &lt;watchdog model='i6300esb'/&gt;
  &lt;/devices&gt;
  ...</pre>
R
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4714

4715 4716 4717 4718 4719 4720
<pre>
  ...
  &lt;devices&gt;
    &lt;watchdog model='i6300esb' action='poweroff'/&gt;
  &lt;/devices&gt;
&lt;/domain&gt;</pre>
R
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4721 4722 4723 4724

    <dl>
      <dt><code>model</code></dt>
      <dd>
M
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4725
        <p>
R
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4726
        The required <code>model</code> attribute specifies what real
M
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4727 4728 4729 4730 4731 4732 4733 4734 4735 4736 4737
        watchdog device is emulated.  Valid values are specific to the
        underlying hypervisor.
        </p>
        <p>
        QEMU and KVM support:
        </p>
        <ul>
          <li> 'i6300esb' &mdash; the recommended device,
            emulating a PCI Intel 6300ESB </li>
          <li> 'ib700' &mdash; emulating an ISA iBase IB700 </li>
        </ul>
R
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4738 4739 4740
      </dd>
      <dt><code>action</code></dt>
      <dd>
M
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4741
        <p>
R
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4742
        The optional <code>action</code> attribute describes what
M
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4743 4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755
        action to take when the watchdog expires.  Valid values are
        specific to the underlying hypervisor.
        </p>
        <p>
        QEMU and KVM support:
        </p>
        <ul>
          <li>'reset' &mdash; default, forcefully reset the guest</li>
          <li>'shutdown' &mdash; gracefully shutdown the guest
            (not recommended) </li>
          <li>'poweroff' &mdash; forcefully power off the guest</li>
          <li>'pause' &mdash; pause the guest</li>
          <li>'none' &mdash; do nothing</li>
4756 4757
          <li>'dump' &mdash; automatically dump the guest
            <span class="since">Since 0.8.7</span></li>
M
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4758 4759
        </ul>
        <p>
4760
        Note 1: the 'shutdown' action requires that the guest
M
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4761 4762 4763 4764 4765
        is responsive to ACPI signals.  In the sort of situations
        where the watchdog has expired, guests are usually unable
        to respond to ACPI signals.  Therefore using 'shutdown'
        is not recommended.
        </p>
4766 4767 4768 4769
        <p>
        Note 2: the directory to save dump files can be configured
        by <code>auto_dump_path</code> in file /etc/libvirt/qemu.conf.
        </p>
R
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4770 4771 4772
      </dd>
    </dl>

4773 4774 4775 4776 4777 4778 4779 4780 4781
    <h4><a name="elementsMemBalloon">Memory balloon device</a></h4>

    <p>
      A virtual memory balloon device is added to all Xen and KVM/QEMU
      guests. It will be seen as <code>memballoon</code> element.
      It will be automatically added when appropriate, so there is no
      need to explicitly add this element in the guest XML unless a
      specific PCI slot needs to be assigned.
      <span class="since">Since 0.8.3, Xen, QEMU and KVM only</span>
4782 4783 4784
      Additionally, <span class="since">since 0.8.4</span>, if the
      memballoon device needs to be explicitly disabled,
      <code>model='none'</code> may be used.
4785 4786 4787
    </p>

    <p>
J
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4788
      Example: automatically added device with KVM
4789 4790 4791 4792 4793 4794 4795 4796 4797
    </p>
<pre>
  ...
  &lt;devices&gt;
    &lt;memballoon model='virtio'/&gt;
  &lt;/devices&gt;
  ...</pre>

    <p>
J
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4798
      Example: manually added device with static PCI slot 2 requested
4799 4800 4801 4802
    </p>
<pre>
  ...
  &lt;devices&gt;
J
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4803 4804
    &lt;memballoon model='virtio'&gt;
      &lt;address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/&gt;
4805
      &lt;stats period='10'/&gt;
J
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4806
    &lt;/memballoon&gt;
4807 4808 4809 4810 4811 4812 4813 4814
  &lt;/devices&gt;
&lt;/domain&gt;</pre>

    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          The required <code>model</code> attribute specifies what type
E
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4815 4816
          of balloon device is provided. Valid values are specific to
          the virtualization platform
4817 4818 4819 4820 4821 4822
        </p>
        <ul>
          <li>'virtio' &mdash; default with QEMU/KVM</li>
          <li>'xen' &mdash; default with Xen</li>
        </ul>
      </dd>
4823 4824 4825 4826 4827
      <dt><code>period</code></dt>
      <dd>
        <p>
          The optional <code>period</code> allows the QEMU virtio memory
          balloon driver to provide statistics through the <code>virsh
4828 4829 4830 4831 4832 4833 4834 4835 4836 4837
          dommemstat [domain]</code> command. By default, collection is
          not enabled. In order to enable, use the <code>virsh dommemstat
          [domain] --period [number]</code> command or <code>virsh edit</code>
          command to add the option to the XML definition.
          The <code>virsh dommemstat</code> will accept the options
          <code>--live</code>, <code>--current</code>, or <code>--config</code>.
          If an option is not provided, the change for a running domain will
          only be made to the active guest.
          If the QEMU driver is not at the right
          revision, the attempt to set the period will fail.
4838 4839 4840
          <span class='since'>Since 1.1.1, requires QEMU 1.5</span>
        </p>
      </dd>
4841
    </dl>
4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856
    <h4><a name="elementsRng">Random number generator device</a></h4>

    <p>
      The virtual random number generator device allows the host to pass
      through entropy to guest operating systems.
      <span class="since">Since 1.0.3</span>
    </p>

    <p>
      Example: usage of the RNG device:
    </p>
<pre>
  ...
  &lt;devices&gt;
    &lt;rng model='virtio'&gt;
4857
      &lt;rate period="2000" bytes="1234"/&gt;
4858 4859 4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879
      &lt;backend model='random'&gt;/dev/random&lt;/backend&gt;
      &lt;!-- OR --&gt;
      &lt;backend model='egd' type='udp'&gt;
        &lt;source mode='bind' service='1234'&gt;
        &lt;source mode='connect' host='1.2.3.4' service='1234'&gt;
      &lt;/backend&gt;
    &lt;/rng&gt;
  &lt;/devices&gt;
  ...
</pre>
    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          The required <code>model</code> attribute specifies what type
          of RNG device is provided. Valid values are specific to
          the virtualization platform:
        </p>
        <ul>
          <li>'virtio' &mdash; supported by qemu and virtio-rng kernel module</li>
        </ul>
      </dd>
4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890 4891
      <dt><code>rate</code></dt>
      <dd>
        <p>
          The optional <code>rate</code> element allows limiting the rate at
          which entropy can be consumed from the source.  The mandatory
          attribute <code>bytes</code> specifies how many bytes are permitted
          to be consumed per period.  An optional <code>period</code> attribute
          specifies the duration of a period in milliseconds; if omitted, the
          period is taken as 1000 milliseconds (1 second).
          <span class='since'>Since 1.0.4</span>
        </p>
      </dd>
4892 4893 4894 4895 4896 4897 4898 4899
      <dt><code>backend</code></dt>
      <dd>
        <p>
          The <code>backend</code> element specifies the source of entropy
          to be used for the domain. The source model is configured using the
          <code>model</code> attribute. Supported source models are:
        </p>
        <ul>
4900 4901
          <li>'random' &mdash; /dev/random (default) or /dev/hwrng
            device as source (for now, no other sources are permitted)</li>
4902 4903 4904
          <li>'egd' &mdash; a EGD protocol backend</li>
        </ul>
      </dd>
4905
      <dt><code>backend model='random'</code></dt>
4906 4907 4908
      <dd>
        <p>
          This backend type expects a non-blocking character device as input.
4909
          The only accepted paths are /dev/random and /dev/hwrng. The file
4910 4911 4912 4913
          name is specified as contents of the <code>backend</code> element.
          When no file name is specified the hypervisor default is used.
        </p>
      </dd>
4914
      <dt><code>backend model='egd'</code></dt>
4915 4916 4917 4918 4919 4920 4921 4922 4923 4924
      <dd>
        <p>
          This backend connects to a source using the EGD protocol.
          The source is specified as a character device. Refer to
          <a href='#elementsCharHostInterface'>character device host interface</a>
          for more information.
        </p>
      </dd>

    </dl>
4925

4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946
    <h4><a name="elementsTpm">TPM device</a></h4>

    <p>
      The TPM device enables a QEMU guest to have access to TPM
      functionality.
    </p>
    <p>
      The TPM passthrough device type provides access to the host's TPM
      for one QEMU guest. No other software may be is using the TPM device,
      typically /dev/tpm0, at the time the QEMU guest is started.
      <span class="since">'passthrough' since 1.0.5</span>
    </p>

    <p>
     Example: usage of the TPM passthrough device
    </p>
<pre>
  ...
  &lt;devices&gt;
    &lt;tpm model='tpm-tis'&gt;
      &lt;backend type='passthrough'&gt;
S
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4947
        &lt;device path='/dev/tpm0'/&gt;
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      &lt;/backend&gt;
    &lt;/tpm&gt;
  &lt;/devices&gt;
  ...
</pre>
    <dl>
      <dt><code>model</code></dt>
      <dd>
        <p>
          The <code>model</code> attribute specifies what device
          model QEMU provides to the guest. If no model name is provided,
          <code>tpm-tis</code> will automatically be chosen.
        </p>
      </dd>
      <dt><code>backend</code></dt>
      <dd>
        <p>
          The <code>backend</code> element specifies the type of
          TPM device. The following types are supported:
        </p>
        <ul>
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          <li>'passthrough' &mdash; use the host's TPM device.</li>
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        </ul>
      </dd>
      <dt><code>backend type='passthrough'</code></dt>
      <dd>
        <p>
          This backend type requires exclusive access to a TPM device on
          the host.
          An example for such a device is /dev/tpm0. The filename is
          specified as path attribute of the <code>source</code> element.
          If no file name is specified then /dev/tpm0 is automatically used.
        </p>
      </dd>
    </dl>

L
Li Zhang 已提交
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    <h4><a name="elementsNVRAM">NVRAM device</a></h4>
    <p>
      nvram device is always added to pSeries guest on PPC64, and its address
      is allowed to be changed.  Element <code>nvram</code> (only valid for
      pSeries guest, <span class="since">since 1.0.5</span>) is provided to
      enable the address setting.
    </p>
    <p>
      Example: usage of NVRAM configuration
    </p>
<pre>
  ...
  &lt;devices&gt;
    &lt;nvram&gt;
      &lt;address type='spapr-vio' reg='0x3000'/&gt;
    &lt;/nvram&gt;
  &lt;/devices&gt;
  ...
</pre>
  <dl>
    <dt><code>spapr-vio</code></dt>
    <dd>
      <p>
        VIO device address type, only valid for PPC64.
      </p>
    </dd>
    <dt><code>reg</code></dt>
    <dd>
      <p>
        Device address
      </p>
    </dd>
  </dl>

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    <h3><a name="seclabel">Security label</a></h3>

    <p>
      The <code>seclabel</code> element allows control over the
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      operation of the security drivers. There are three basic
      modes of operation, 'dynamic' where libvirt automatically
      generates a unique security label, 'static' where the
      application/administrator chooses the labels, or 'none'
      where confinement is disabled. With dynamic
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      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
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      if desired.  <span class="since">'dynamic' since 0.6.1, 'static'
      since 0.6.2, and 'none' since 0.9.10.</span>
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    </p>

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    <p>
      If more than one security driver is used by libvirt, multiple
      <code>seclabel</code> tags can be used, one for each driver and
      the security driver referenced by each tag can be defined using
      the attribute <code>model</code>
    </p>

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    <p>
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      Valid input XML configurations for the top-level security label
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      are:
    </p>

    <pre>
  &lt;seclabel type='dynamic' model='selinux'/&gt;

  &lt;seclabel type='dynamic' model='selinux'&gt;
    &lt;baselabel&gt;system_u:system_r:my_svirt_t:s0&lt;/baselabel&gt;
  &lt;/seclabel&gt;

  &lt;seclabel type='static' model='selinux' relabel='no'&gt;
    &lt;label&gt;system_u:system_r:svirt_t:s0:c392,c662&lt;/label&gt;
  &lt;/seclabel&gt;

  &lt;seclabel type='static' model='selinux' relabel='yes'&gt;
    &lt;label&gt;system_u:system_r:svirt_t:s0:c392,c662&lt;/label&gt;
  &lt;/seclabel&gt;
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  &lt;seclabel type='none'/&gt;
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    </pre>

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    <p>
      If no 'type' attribute is provided in the input XML, then
      the security driver default setting will be used, which
      may be either 'none' or 'dynamic'. If a 'baselabel' is set
      but no 'type' is set, then the type is presumed to be 'dynamic'
    </p>

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    <p>
      When viewing the XML for a running guest with automatic
      resource relabeling active, an additional XML element,
      <code>imagelabel</code>, will be included. This is an
      output-only element, so will be ignored in user supplied
      XML documents
    </p>
    <dl>
      <dt><code>type</code></dt>
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      <dd>Either <code>static</code>, <code>dynamic</code> or <code>none</code>
        to determine whether libvirt automatically generates a unique security
        label or not.
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      </dd>
      <dt><code>model</code></dt>
      <dd>A valid security model name, matching the currently
        activated security model
      </dd>
      <dt><code>relabel</code></dt>
      <dd>Either <code>yes</code> or <code>no</code>. This must always
        be <code>yes</code> if dynamic label assignment is used. With
        static label assignment it will default to <code>no</code>.
      </dd>
      <dt><code>label</code></dt>
      <dd>If static labelling is used, this must specify the full
        security label to assign to the virtual domain. The format
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        of the content depends on the security driver in use:
        <ul>
          <li>SELinux: a SELinux context.</li>
          <li>AppArmor: an AppArmor profile.</li>
          <li>
            DAC: owner and group separated by colon. They can be
            defined both as user/group names or uid/gid. The driver will first
            try to parse these values as names, but a leading plus sign can
            used to force the driver to parse them as uid or gid.
          </li>
        </ul>
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      </dd>
      <dt><code>baselabel</code></dt>
      <dd>If dynamic labelling is used, this can optionally be
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        used to specify the base security label that will be used to generate
        the actual label. The format of the content depends on the security
        driver in use.

        The SELinux driver uses only the <code>type</code> field of the
        baselabel in the generated label. Other fields are inherited from
        the parent process when using SELinux baselabels.

        (The example above demonstrates the use of <code>my_svirt_t</code>
        as the value for the <code>type</code> field.)
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      </dd>
      <dt><code>imagelabel</code></dt>
      <dd>This is an output only element, which shows the
        security label used on resources associated with the virtual domain.
        The format of the content depends on the security driver in use
      </dd>
    </dl>

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    <p>When relabeling is in effect, it is also possible to fine-tune
      the labeling done for specific source file names, by either
      disabling the labeling (useful if the file lives on NFS or other
      file system that lacks security labeling) or requesting an
      alternate label (useful when a management application creates a
      special label to allow sharing of some, but not all, resources
      between domains), <span class="since">since 0.9.9</span>.  When
      a <code>seclabel</code> element is attached to a specific path
      rather than the top-level domain assignment, only the
      attribute <code>relabel</code> or the
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      sub-element <code>label</code> are supported.  Additionally,
      <span class="since">since 1.1.2</span>, an output-only
      element <code>labelskip</code> will be present for active
      domains on disks where labeling was skipped due to the image
      being on a file system that lacks security labeling.
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    </p>

D
Daniel P. Berrange 已提交
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    <h2><a name="examples">Example configs</a></h2>
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    <p>
      Example configurations for each driver are provide on the
      driver specific pages listed below
    </p>

    <ul>
      <li><a href="drvxen.html#xmlconfig">Xen examples</a></li>
      <li><a href="drvqemu.html#xmlconfig">QEMU/KVM examples</a></li>
    </ul>
  </body>
</html>