Comment 2 for bug 861260

OK - so it looks like the filesystem associated with instance-00000006 had been remounted ro due to some sort of underlying IO error.

However this has highlighted that if nova-common is upgraded whilst there are running lxc instances the filesystem permissions within the root filesystem associated with the instance also get changed to nova:nova.

I also noticed that the group of the nova user is not changed - so new files are still created with use nogroup.

This second point only effects upgrades, not fresh installations.