Qemu-guest-agent

Introduction - What is qemu-guest-agent

The qemu-guest-agent is a helper daemon, which is installed in the guest. It is used to exchange information between the host and guest, and to execute command in the guest.

In Proxmox VE, the qemu-guest-agent is used for mainly two things:

1. To properly shutdown the guest, instead of relying on ACPI commands or windows policies
2. To freeze the guest file system when making a backup (on windows, use the volume shadow copy service VSS).

Installation

Host

You have to enable the guest-agent per VM, either set it in the GUI to "Yes" under options (see screenshot):

or via CLI:

qm set VMID -agent 1

Guest

Linux

On Linux you have to simply install the qemu-guest-agent, please refer to the documentation of your system.

We show here the commands for Debian/Ubuntu and Redhat based systems:

on Debian/Ubuntu based systems (with apt-get) run:

apt-get install qemu-guest-agent

and on Redhat based systems (with yum):

yum install qemu-guest-agent

Windows

First you have to download the virtio-win driver iso (see Windows VirtIO Drivers).

Then install the virtio-serial driver:

1. Attach the ISO to your windows VM (virtio-*.iso)
2. Go to the windows Device Manager
3. Look for "PCI Simple Communications Controller"
4. Right Click -> Update Driver and select on the mounted iso in DRIVE:\vioserial\<OSVERSION>\ where <OSVERSION> is your Windows Version (e.g. 2k12R2 for Windows 2012 R2)

After that, you have to install the qemu-guest-agent:

1. Go to the mounted ISO in explorer
2. Execute the installer with double click (either qemu-ga-x64.msi (64-bit) or qemu-ga-x86.msi (32-bit)

After that the qemu-guest-agent should be up and running. You can validate this in the list of Window Services, or in a PowerShell with:

PS C:\Users\Administrator> Get-Service QEMU-GA

Status   Name               DisplayName
------   ----               -----------
Running  QEMU-GA            QEMU Guest Agent

The qemu guest agent runs default as "Network Service" Windows user and this user has default not the permission to run the vss writer. If you want the ability to run the vss and profit from consistence snapshots you have to grand this service this permission.

Testing that the communication with the guest agent is working

The communication with the guest agent takes place over a unix socket located in /var/run/qemu-server/<my_vmid>.gqa You can test the communication qm agent:

qm agent <vmid> ping

if the qemu-guest-agent is correctly runnning in the VM, it will return without an error massage.

See Also

http://wiki.qemu.org/Features/GuestAgent