Proxmox vm's use the QEMU guest agent. The official documentation from Proxmox can be found here: https://pve.proxmox.com/wiki/Qemu-guest-agent

• Open the Proxmox VE UI
• Open the vm
• Options
• QEMU Guest Agent
• Check: Use QEMU Guest Agent
• Power off the vm and start it again

If this option is set, a new virtual serial device is shown to the vm, which will be accessed by the agent which will be installed in the guest os.

To set this option via cli use the following command:

qm set VMID --agent 1

Per default the qemu-guest-agent doesn't allow command execution. You will see the following error message, if you try it:

root@mypve:~# qm guest exec 101 /bin/ls
Agent error: The command guest-exec has been disabled for this instance

Open the config file.

vi /etc/sysconfig/qemu-ga

Search for the blacklist line.

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

Remove guest-exec (and guest-exec-status for async exec calls).

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

Restart the agent.

systemctl restart qemu-guest-agent

qm guest exec <vmid> <command> <arg1> <arg2> ...

root@mypve:~# qm guest exec 101 /bin/ls -- "-la" "/etc/hosts"
{
   "exitcode" : 0,
   "exited" : 1,
   "out-data" : "-rw-r--r--. 1 root root 158 Sep 10  2018 /etc/hosts\n"
}

• Download the latest VirtIO ISO (Fedora VirtIO Archive)
• Mount the ISO to the vm
• Open the device manager
• Search the device “PCI Simple Communications Controller”
• Install the driver for this device from the mounted ISO
• Start the Guest Agent installer from the mounted ISO (“X:\guest-agent\qemu-ga-x86_64.msi”)
• Reboot the vm

For Debian/Ubuntu based systems:

apt install qemu-guest-agent

For RedHat based systems:

yum install qemu-guest-agent

Start the service:

systemctl start qemu-guest-agent

Starting the systemd unit file takes a long time and fails. You see the following errors in the journal:

Apr 10 18:14:39 pmg systemd[1]: dev-virtio\x2dports-org.qemu.guest_agent.0.device: Job dev-virtio\x2dports-org.qemu.guest_agent.0.device/start ti
Apr 10 18:14:39 pmg systemd[1]: Timed out waiting for device /dev/virtio-ports/org.qemu.guest_agent.0.

You probably forgot to enable the QEMU Guest Agent setting in the vm settings.

If the QEMU Guest Agent service is startet but in the vm overview you see “QEMU Guest Agent not running” then you probably forgot to enable the QEMU Guest Agent setting in the vm settings.