Upgrading to 2011.3-0ubuntu3 failed:
Setting up nova-common (2011.3-0ubuntu3) ...^M
^M
Configuration file `/etc/nova/nova.conf'^M
==> Modified (by you or by a script) since installation.^M
==> Package distributor has shipped an updated version.^M
What would you like to do about it ? Your options are:^M
Y or I : install the package maintainer's version^M
N or O : keep your currently-installed version^M
D : show the differences between the versions^M
Z : start a shell to examine the situation^M
The default action is to keep your current version.^M
*** nova.conf (Y/I/N/O/D/Z) [default=N] ? n^M
chown: changing ownership of `/var/lib/nova/instances/instance-00000006/rootfs': Read-only file system^M
dpkg: error processing nova-common (--configure):^M
subprocess installed post-installation script returned error exit status 1^M
dpkg: dependency problems prevent configuration of nova-network:^M
nova-network depends on nova-common (= 2011.3-0ubuntu3); however:^M
Package nova-common is not configured yet.^M
dpkg: error processing nova-network (--configure):^M
dependency problems - leaving unconfigured^M
dpkg: dependency problems prevent configuration of nova-compute:^M
nova-compute depends on nova-common (= 2011.3-0ubuntu3); however:^M
Package nova-common is not configured yet.^M
dpkg: error processing nova-compute (--configure):^M
dependency problems - leaving unconfigured^M
dpkg: dependency problems prevent configuration of nova-compute-lxc:^M
nova-compute-lxc depends on nova-compute (= 2011.3-0ubuntu3); however:^M
Package nova-compute is not configured yet.^M
dpkg: error processing nova-compute-lxc (--configure):^M
dependency problems - leaving unconfigured^M
dpkg: dependency problems prevent configuration of nova-api:^M
nova-api depends on nova-common (= 2011.3-0ubuntu3); however:^M
Package nova-common is not configured yet.^M
dpkg: error processing nova-api (--configure):^M
dependency problems - leaving unconfigured^M
ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: nova-common 2011.3-0ubuntu3
ProcVersionSignature: Ubuntu 3.0.0-1204.9-omap4 3.0.3
Uname: Linux 3.0.0-1204-omap4 armv7l
ApportVersion: 1.23-0ubuntu1
Architecture: armel
Date: Wed Sep 28 09:58:57 2011
NovaConf: Error: [Errno 13] Permission denied: '/etc/nova/nova.conf'
PackageArchitecture: all
SourcePackage: nova
UpgradeStatus: No upgrade log present (probably fresh install)
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.