libvirt/docs/drvxen.html.in

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<h1>Xen hypervisor driver</h1>
<p>
The libvirt Xen driver provides the ability to manage virtual machines
on any Xen release from 3.0.1 onwards.
</p>
<h2>Deployment pre-requisites</h2>
<p>
The libvirt Xen driver uses a combination of channels to manage Xen
virtual machines.
</p>
<ul>
<li>
<strong>XenD</strong>: Access to the Xen daemon is a mandatory
requirement for the libvirt Xen driver. It requires that the UNIX
socket interface be enabled in the <code>/etc/xen/xend-config.sxp</code>
configuration file. Specifically the config settings
<code>(xend-unix-server yes)</code>. This path is usually restricted
to only allow the <code>root</code> user access. As an alternative,
the HTTP interface can be used, however, this has significant security
implications.
</li>
<li>
<strong>XenStoreD</strong>: Access to the Xenstore daemon enables
more efficient codepaths for looking up domain information which
lowers the CPU overhead of management.
</li>
<li>
<strong>Hypercalls</strong>: The ability to make direct hypercalls
allows the most efficient codepaths in the driver to be used for
monitoring domain status.
</li>
<li>
<strong>XM config</strong>: When using Xen releases prior to 3.0.4,
there is no inactive domain management in XenD. For such releases,
libvirt will automatically process XM configuration files kept in
the <code>/etc/xen</code> directory. It is important not to place
any other non-config files in this directory.
</li>
</ul>
<h2><a name="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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