Unreliable QEMU guest agent responses

Question

I have a script for automatic backups of my KVMs. Before taking a LVM snapshot I'm trying to freeze the filesystems of the KVM with the QEMU guest agent. It works good most of the time but randomly I don't receive a direct answer from the guest agent or I receive messages like the following when running fs-freeze:

Guest agent is not responding: Guest agent not available for now

... or different error messages. The problem is that the filesystems are frozen anyway. So when my backup script stops at this point (because it expects proper exit status/code) my KVM will be frozen and will therefore be unreachable until it is thawed again!

Is there an alternative way to freeze the filesystems of a KVM? I'd like to access the qemu "console" for these KVMs directly and run the fs-freeze manually.

Answer 1

I found out that I can simply use the "fsfreeze" command that comes with the util-linux package:

Usage:
 fsfreeze [options] <mount point>

Options:
 -h, --help        this help
 -f, --freeze      freeze the filesystem
 -u, --unfreeze    unfreeze the filesystem

For more information see fsfreeze(8).