Revision as of 09:43, 13 September 2013

The Qemu Guest Agent permits access to a VM via a virtual serial socket. This has the advantage that the VM can be accessed via the VM node (hypervisor) without network connection or remote desktop protocol.

Libvirt

The XML must be amended by the following XML snippet in the devices section:

<channel type="unix">
  <source mode="bind"/>
  <target type="virtio" name="org.qemu.guest_agent.0"/>
</channel>

This will create a new virtual serial device within the VM and a new socket under code>/var/lib/libvirt/qemu/channel/target/</code> (make sure that this directory is protected!) named /var/lib/libvirt/qemu/channel/target/${VMNAME}.org.qemu.guest_agent.0.

Please note: since libvirt will automatically listen on that socket one can not use a tool like qemu-ga-client to anything on it, everything has to go via libvirt.

VM

In the VM one must install and start the qemu-guest-agent.

On Gentoo this means:

emerge qemu-guest-agent
/etc/init.d/qemu-guest-agentqemu-guest-agent
rc-update add qemu-guest-agent default

Test

Shutdown a VM via qemu-ga

The advantage of using qemu-ga instead of the ACPI-based mechanism to shutdown a VM is that you get a confirmation if the qemu-ga was able to issue shutdown -P within the VM whereas with ACPI you won't even know whether the guest OS has received the event.

virsh shutdown --mode agent $VMNAME

Example:

~ # virsh shutdown --mode agent bc58f697-1f21-4613-9f4d-469cdaff0621Domain bc58f697-1f21-4613-9f4d-469cdaff0621 is being shutdown

Ping qemu-ga via libvirt

virsh qemu-agent-command $VMNAME'{"execute":"guest-ping"}'

Example:

~ # virsh qemu-agent-command bc58f697-1f21-4613-9f4d-469cdaff0621 '{"execute":"guest-ping"}'

{"return":{}}

Links

• http://wiki.libvirt.org/page/Qemu_guest_agent
• http://wiki.qemu.org/Features/QAPI/GuestAgent