Added info for Proxmox guest agent

Proxmox/Qemu-guest-agent - Proxmox VE.url

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+[InternetShortcut]
+URL=https://pve.proxmox.com/wiki/Qemu-guest-agent

Proxmox/client_agent.md

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+# 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 three 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/snapshot (on windows, use the volume shadow copy service VSS). If the guest agent is enabled and running, it calls guest-fsfreeze-freeze and guest-fsfreeze-thaw to improve consistency.
+3. In the phase when the guest (VM) is resumed after pause (for example after shapshot) it immediately synchronizes its time with the hypervisor using qemu-guest-agent (as first step).
+
+## Installation
+
+### Host
+
+You have to install guest-agent in each VM and then enable it, you can do that in the Proxmox VE Webinterface (GUI)
+
+QEMU Guest Agent Option
+
+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``
+
+Depending on the distribution, the guest agent might not start automatically after the installation.
+
+Start it either directly with
+
+``systemctl start qemu-guest-agent``
+
+Then enable the service to autostart (permanently) if not auto started, with
+
+``systemctl enable qemu-guest-agent``
+
+(should work for most distributions) or reboot the guest.
+
+#### 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. The guest agent installer is in the directory ``guest-agent``
+3. Execute the installer with double click (either ``qemu-ga-x86_64.msi`` (64-bit) or ``qemu-ga-i386.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
+```
+
+If it is not running, you can use the **Services** control panel to start it and make sure that it will start automatically on the next boot.
+
+### 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>.qga 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 message.
+