How to check and restore QEMU Guest Agent?

QEMU Guest Agent is a daemon program that is installed on a VM. QEMU Guest Agent provides execution of commands on VMs and information exchange between VMs and the cluster node.

VMmanager uses QEMU Guest Agent to change network settings without rebooting. If the QEMU Guest Agent is unavailable for the platform for five minutes, VMmanager will reboot the VM to apply the settings.

To manage VM with CentOS OS, guest-exec function should be enabled in QEMU Guest Agent.

To avoid an unplanned reboot of the VM, you can check the status of the QEMU Guest Agent before changing the settings. This can be done on a VM or the cluster node.

Diagnostics

1. Connect to the VM via SSH.

2. Define the status of the QEMU Guest Agent:

   systemctl status qemu-guest-agent

   CODE

    Examples of responses:

   QEMU Guest Agent is running

   ● qemu-guest-agent.service - QEMU Guest Agent
      Loaded: loaded (/usr/lib/systemd/system/qemu-guest-agent.service; enabled; vendor preset: enabled)
      Active: active (running) since Вт 2021-08-10 05:25:54 UTC; 1 weeks 3 days ago

   CODE

   QEMU Guest Agent is stopped

   ● qemu-guest-agent.service - QEMU Guest Agent
      Loaded: loaded (/usr/lib/systemd/system/qemu-guest-agent.service; enabled; vendor preset: enabled)
      Active: inactive (dead) since Пт 2021-08-20 06:27:16 UTC; 2s ag

   CODE

   QEMU Guest Agent is not installed

   Unit qemu-guest-agent.service could not be found.

   CODE

Restoring work

If QEMU Guest Agent is not installed

1. Connect to the VM via SSH.

2. Install QEMU Guest Agent:

   CentOS

   yum install qemu-guest-agent

   CODE

   Debian, Ubuntu

   apt install qemu-guest-agent

   CODE

3. Add QEMU Guest Agent to the autostart:

   systemctl enable --now qemu-guest-agent

   CODE

4. Check the status of QEMU Guest Agent:

   systemctl status qemu-guest-agent

   CODE

5. Check the status of the SELinux service:

   sestatus

   CODE

   If the status is different from disable:

   1. Disable SELinux. Replace the below line in the /etc/selinux/config file

      SELINUX=enforcing

      CODE

      with

      SELINUX=disabled

      CODE
   2. Reboot the VM.

6. The file /etc/sysconfig/qemu-ga contains a line the below format

   BLACKLIST_RPC=guest-file-open,guest-file-close,guest-file-read,guest-file-write,guest-file-seek,guest-file-flush,guest-exec,guest-exec-status

   CODE

   
   

   1. Mark this line as comment or delete it.

   2. Restart QEMU Guest Agent:

      systemctl restart qemu-guest-agent

      CODE

If QEMU Guest Agent is stopped

1. Connect to the VM via SSH.

2. Start QEMU Guest Agent:

   systemctl start qemu-guest-agent

   CODE

If guest-exec function is disabled

1. Connect to the VM via SSH.

2. Run the command: 

   sed -i '/BLACKLIST_RPC=/cBLACKLIST_RPC=' /etc/sysconfig/qemu-ga

   BASH

3. Restart QEMU Guest Agent:

   systemctl restart qemu-guest-agent

   CODE