VMM qemu stuck in a saved state – part 2 – macvtap

Scroll to bottom of post for the summary of my slightly better way to recover a saved state qemu VM that refuses to boot.

After today’s software updates, including a new kernel, I was asked to restart and promptly did so, again forgetting about my running VM server.  When I came to start up the webserver after logging back in I found the dreaded “saved” state power on problem:

Error restoring domain: error creating macvtap type of interface: Device or resource busy

Rather than my usual dirty hack to get it working (deleting the saved state from the filesystem) I decided to try and fix it.  I had a quick search online but didn’t see anything that instantly make me think it was the answer.  Instead I resorted to a bit of experimentation.  Since I know macvtap is the something to do with the virtual network so I decided to stop the NAT network from the Virtual Networks tab in the VMM and tried running the guest VM.  It didn’t work as it said the NAT network wasn’t available (no surprises there).  On restarting the NAT and then trying to run the guest VM again, it worked!  The little loading window did its progress bar thing for a few seconds then the machine popped up its monitor power saver mode at the login prompt I left it at before the restart.

It might be a better bet to go to the VMM’s Network Interfaces tab and find your macvtap network and restart that.  I’m assuming macvtap networks are all named tapX where X is a number, mine is tap0.

Slightly improved solution

  1. Disable your VMM network(s)
  2. Try to resume the VM (might not be necessary)
  3. Re-enable your VMM networks.
  4. Resume the VM.

Step 2 might not be required, however its what I did and my machine came back to life.  This obviously isn’t a fix for the underlying problem, but it does get you back to work after you’ve experienced the problem.

I’m a step closer to actually solving this, its just a shame I don’t know how many steps there will be, I’m hoping for 3 however it could be 300…