VMmanager 6: Administrator guide

How to check and restore QEMU Guest Agent?

ISPSystem

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 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 on the VM


  1. Connect to the VM via SSH.

  2. Define the status of the QEMU Guest Agent:

    systemctl status qemu-guest-agent

     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
    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
    QEMU Guest Agent is not installed
    Unit qemu-guest-agent.service could not be found.

Diagnostics on the cluster node


  1. Connect to the cluster node via SSH.
  2. Define the status of the QEMU Guest Agent:

    virsh qemu-agent-command <vm_id>_<vm_name> '{"execute": "guest-info", "arguments": {}}'
    <vm_id>_<vm_name> — file name of the VM containing the id and name of the VM. For example, for a VM with id 12 and the name of test-vm, the file name should be 12_test_vm

    If QEMU Guest Agent is running, you will get a response as shown below:

    Fragment of response in JSON
    {"return":{"version":"2.12.0","supported_commands":[{"enabled":true,"name":"guest-get-osinfo","success-response":true}

     If QEMU Guest Agent is not running or is stopped, you will get a response as shown below:

    error: Guest agent is not responding: QEMU guest agent is not connected

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
    Debian, Ubuntu
    apt install qemu-guest-agent
  3. Add QEMU Guest Agent to the autostart:

    systemctl enable --now qemu-guest-agent
  4. Check the status of QEMU Guest Agent:

    systemctl status qemu-guest-agent
  5. Check the status of the SELinux service:

    sestatus

    If the status is different from disable:

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

      SELINUX=enforcing

      with

      SELINUX=disabled
    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


    1. Mark this line as comment or delete it.
    2. Restart QEMU Guest Agent:

      systemctl restart qemu-guest-agent

If QEMU Guest Agent is stopped

  1. Connect to the VM via SSH.
  2. Start QEMU Guest Agent:

    systemctl start qemu-guest-agent

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