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    <h1>libxl hypervisor driver for Xen</h1>

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

    <p>
      The libvirt libxl driver provides the ability to manage virtual
      machines on any Xen release from 4.6.0 onwards.
    </p>

    <h2><a id="project">Project Links</a></h2>

    <ul>
      <li>
        The <a href="https://www.xenproject.org">Xen</a>
        hypervisor on Linux and Solaris hosts
      </li>
    </ul>

    <h2><a id="prereq">Deployment pre-requisites</a></h2>

    <p>
      The libvirt libxl driver uses Xen's libxl API, also known as
      libxenlight, to implement libvirt's hypervisor driver
      functionality. libxl provides a consolidated interface for
      managing a Xen host and its virtual machines, unlike old
      versions of Xen where applications often had to communicate
      with xend, xenstored, and the hypervisor itself via hypercalls.
      With libxl the only pre-requisit is a properly installed Xen
      host with the libxl toolstack running in a service domain
      (often Domain-0).
    </p>

    <h2><a id="uri">Connections to libxl driver</a></h2>

    <p>
      The libvirt libxl driver is a single-instance privileged driver,
      with a driver name of 'xen'. Some example connection URIs for
      the libxl driver are:
    </p>

<pre>
xen:///system                     (local access, direct)
xen+unix:///system                (local access, via daemon)
xen://example.com/system          (remote access, TLS/x509)
xen+tcp://example.com/system      (remote access, SASl/Kerberos)
xen+ssh://root@example.com/system (remote access, SSH tunnelled)
</pre>

    <h2><a id="imex">Import and export of libvirt domain XML configs</a></h2>

    <p>
      The libxl driver currently supports three native
      config formats. The first, known as <code>xen-xm</code>, is the
      original Xen virtual machine config format used by the legacy
      xm/xend toolstack. The second, known as <code>xen-sxpr</code>,
      is also one of the original formats that was used by xend's
      legacy HTTP RPC service (<span class='removed'>removed in 5.6.0</span>)
    </p>

    <p>
      The third format is <code>xen-xl</code>, which is the virtual
      machine config format supported by modern Xen. The <code>xen-xl</code>
      format is described in the xl.cfg(5) man page.
    </p>

    <h3><a id="xmlimport">Converting from XM config files to domain XML</a></h3>

    <p>
      The <code>virsh domxml-from-native</code> provides a way to convert an
      existing set of xl, xm, or sxpr config files to libvirt Domain XML,
      which can then be used by libvirt.
    </p>

    <pre>$ virsh -c xen:///system domxml-from-native xen-xm rhel5.cfg
&lt;domain type='xen'&gt;
  &lt;name&gt;rhel5pv&lt;/name&gt;
  &lt;uuid&gt;8f07fe28-753f-2729-d76d-bdbd892f949a&lt;/uuid&gt;
  &lt;memory&gt;2560000&lt;/memory&gt;
  &lt;currentMemory&gt;307200&lt;/currentMemory&gt;
  &lt;vcpu&gt;4&lt;/vcpu&gt;
  &lt;bootloader&gt;/usr/bin/pygrub&lt;/bootloader&gt;
  &lt;os&gt;
    &lt;type arch='x86_64' machine='xenpv'&gt;linux&lt;/type&gt;
  &lt;/os&gt;
  &lt;clock offset='utc'/&gt;
  &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;
  &lt;devices&gt;
    &lt;disk type='file' device='disk'&gt;
      &lt;driver name='tap' type='aio'/&gt;
      &lt;source file='/var/lib/xen/images/rhel5pv.img'/&gt;
      &lt;target dev='xvda' bus='xen'/&gt;
    &lt;/disk&gt;
    &lt;disk type='file' device='disk'&gt;
      &lt;driver name='tap' type='qcow'/&gt;
      &lt;source file='/root/qcow1-xen.img'/&gt;
      &lt;target dev='xvdd' bus='xen'/&gt;
    &lt;/disk&gt;
    &lt;interface type='bridge'&gt;
      &lt;mac address='00:16:3e:60:36:ba'/&gt;
      &lt;source bridge='xenbr0'/&gt;
    &lt;/interface&gt;
    &lt;console type='pty'&gt;
      &lt;target port='0'/&gt;
    &lt;/console&gt;
    &lt;input type='mouse' bus='xen'/&gt;
    &lt;graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0'/&gt;
  &lt;/devices&gt;
&lt;/domain&gt;</pre>

    <h3><a id="xmlexport">Converting from domain XML to XM config files</a></h3>

    <p>
      The <code>virsh domxml-to-native</code> provides a way to convert a
      guest description using libvirt Domain XML into xl, xm, or sxpr config
      format.
    </p>

    <pre>$ virsh -c xen:///system domxml-to-native xen-xm rhel5pv.xml
name = "rhel5pv"
uuid = "8f07fe28-753f-2729-d76d-bdbd892f949a"
maxmem = 2500
memory = 300
vcpus = 4
bootloader = "/usr/bin/pygrub"
kernel = "/var/lib/xen/boot_kernel.0YK-cS"
ramdisk = "/var/lib/xen/boot_ramdisk.vWgrxK"
extra = "ro root=/dev/VolGroup00/LogVol00 rhgb quiet"
on_poweroff = "destroy"
on_reboot = "restart"
on_crash = "restart"
sdl = 0
vnc = 1
vncunused = 1
vnclisten = "0.0.0.0"
disk = [ "tap:aio:/var/lib/xen/images/rhel5pv.img,xvda,w", "tap:qcow:/root/qcow1-xen.img,xvdd,w" ]
vif = [ "mac=00:16:3e:60:36:ba,bridge=virbr0,script=vif-bridge,vifname=vif5.0" ]</pre>

    <h2><a id="xmlconfig">Example domain XML config</a></h2>

    <p>
      Below are some example XML configurations for Xen guest domains.
      For full details of the available options, consult the <a href="formatdomain.html">domain XML format</a>
      guide.
    </p>

    <h3>Paravirtualized guest bootloader</h3>

    <p>
      Using a bootloader allows a paravirtualized guest to be booted using
      a kernel stored inside its virtual disk image
    </p>

        <pre>&lt;domain type='xen' &gt;
  &lt;name&gt;fc8&lt;/name&gt;
  &lt;bootloader&gt;/usr/bin/pygrub&lt;/bootloader&gt;
  &lt;os&gt;
    &lt;type&gt;linux&lt;/type&gt;
  &lt;/os&gt;
  &lt;memory&gt;131072&lt;/memory&gt;
  &lt;vcpu&gt;1&lt;/vcpu&gt;
  &lt;devices&gt;
    &lt;disk type='file'&gt;
      &lt;source file='/var/lib/xen/images/fc4.img'/&gt;
      &lt;target dev='sda1'/&gt;
    &lt;/disk&gt;
    &lt;interface type='bridge'&gt;
      &lt;source bridge='xenbr0'/&gt;
      &lt;mac address='aa:00:00:00:00:11'/&gt;
      &lt;script path='/etc/xen/scripts/vif-bridge'/&gt;
    &lt;/interface&gt;
    &lt;console tty='/dev/pts/5'/&gt;
  &lt;/devices&gt;
&lt;/domain&gt;</pre>

    <h3>Paravirtualized guest direct kernel boot</h3>

    <p>
      For installation of paravirtualized guests it is typical to boot the
      domain using a kernel and initrd stored in the host OS
    </p>

        <pre>&lt;domain type='xen' &gt;
  &lt;name&gt;fc8&lt;/name&gt;
  &lt;os&gt;
    &lt;type&gt;linux&lt;/type&gt;
    &lt;kernel&gt;/var/lib/xen/install/vmlinuz-fedora8-x86_64&lt;/kernel&gt;
    &lt;initrd&gt;/var/lib/xen/install/initrd-vmlinuz-fedora8-x86_64&lt;/initrd&gt;
    &lt;cmdline&gt; kickstart=http://example.com/myguest.ks &lt;/cmdline&gt;
  &lt;/os&gt;
  &lt;memory&gt;131072&lt;/memory&gt;
  &lt;vcpu&gt;1&lt;/vcpu&gt;
  &lt;devices&gt;
    &lt;disk type='file'&gt;
      &lt;source file='/var/lib/xen/images/fc4.img'/&gt;
      &lt;target dev='sda1'/&gt;
    &lt;/disk&gt;
    &lt;interface type='bridge'&gt;
      &lt;source bridge='xenbr0'/&gt;
      &lt;mac address='aa:00:00:00:00:11'/&gt;
      &lt;script path='/etc/xen/scripts/vif-bridge'/&gt;
    &lt;/interface&gt;
    &lt;graphics type='vnc' port='-1'/&gt;
    &lt;console tty='/dev/pts/5'/&gt;
  &lt;/devices&gt;
&lt;/domain&gt;</pre>

    <h3>Fullyvirtualized guest BIOS boot</h3>

    <p>
      Fullyvirtualized guests use the emulated BIOS to boot off the primary
      harddisk, CDROM or Network PXE ROM.
    </p>

        <pre>&lt;domain type='xen' id='3'&gt;
  &lt;name&gt;fv0&lt;/name&gt;
  &lt;uuid&gt;4dea22b31d52d8f32516782e98ab3fa0&lt;/uuid&gt;
  &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;
  &lt;/os&gt;
  &lt;memory&gt;524288&lt;/memory&gt;
  &lt;vcpu&gt;1&lt;/vcpu&gt;
  &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;
  &lt;features&gt;
    &lt;pae/&gt;
    &lt;acpi/&gt;
    &lt;apic/&gt;
  &lt;/features&gt;
  &lt;clock sync="localtime"/&gt;
  &lt;devices&gt;
    &lt;emulator&gt;/usr/lib/xen/bin/qemu-dm&lt;/emulator&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;
    &lt;/interface&gt;
    &lt;disk type='file'&gt;
      &lt;source file='/var/lib/xen/images/fv0'/&gt;
      &lt;target dev='hda'/&gt;
    &lt;/disk&gt;
    &lt;disk type='file' device='cdrom'&gt;
      &lt;source file='/var/lib/xen/images/fc5-x86_64-boot.iso'/&gt;
      &lt;target dev='hdc'/&gt;
      &lt;readonly/&gt;
    &lt;/disk&gt;
    &lt;disk type='file' device='floppy'&gt;
      &lt;source file='/root/fd.img'/&gt;
      &lt;target dev='fda'/&gt;
    &lt;/disk&gt;
    &lt;graphics type='vnc' port='5904'/&gt;
  &lt;/devices&gt;
&lt;/domain&gt;</pre>

    <h3>Fullyvirtualized guest direct kernel boot</h3>

    <p>
      With Xen 3.2.0 or later it is possible to bypass the BIOS and directly
      boot a Linux kernel and initrd as a fullyvirtualized domain. This allows
      for complete automation of OS installation, for example using the Anaconda
      kickstart support.
    </p>

        <pre>&lt;domain type='xen' id='3'&gt;
  &lt;name&gt;fv0&lt;/name&gt;
  &lt;uuid&gt;4dea22b31d52d8f32516782e98ab3fa0&lt;/uuid&gt;
  &lt;os&gt;
    &lt;type&gt;hvm&lt;/type&gt;
    &lt;loader&gt;/usr/lib/xen/boot/hvmloader&lt;/loader&gt;
    &lt;kernel&gt;/var/lib/xen/install/vmlinuz-fedora8-x86_64&lt;/kernel&gt;
    &lt;initrd&gt;/var/lib/xen/install/initrd-vmlinuz-fedora8-x86_64&lt;/initrd&gt;
    &lt;cmdline&gt; kickstart=http://example.com/myguest.ks &lt;/cmdline&gt;
  &lt;/os&gt;
  &lt;memory&gt;524288&lt;/memory&gt;
  &lt;vcpu&gt;1&lt;/vcpu&gt;
  &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;
  &lt;features&gt;
    &lt;pae/&gt;
    &lt;acpi/&gt;
    &lt;apic/&gt;
  &lt;/features&gt;
  &lt;clock sync="localtime"/&gt;
  &lt;devices&gt;
    &lt;emulator&gt;/usr/lib/xen/bin/qemu-dm&lt;/emulator&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;
    &lt;/interface&gt;
    &lt;disk type='file'&gt;
      &lt;source file='/var/lib/xen/images/fv0'/&gt;
      &lt;target dev='hda'/&gt;
    &lt;/disk&gt;
    &lt;disk type='file' device='cdrom'&gt;
      &lt;source file='/var/lib/xen/images/fc5-x86_64-boot.iso'/&gt;
      &lt;target dev='hdc'/&gt;
      &lt;readonly/&gt;
    &lt;/disk&gt;
    &lt;disk type='file' device='floppy'&gt;
      &lt;source file='/root/fd.img'/&gt;
      &lt;target dev='fda'/&gt;
    &lt;/disk&gt;
    &lt;graphics type='vnc' port='5904'/&gt;
  &lt;/devices&gt;
&lt;/domain&gt;</pre>

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