I thought I knew the answer to this, but not quite. The problem seems to be related to the fact that my Lucid install is directly descended from Jaunty (Alpha 2 I think it was) – i.e. I haven't done a clean install on this particular drive since then, I've just been upgrading through the release and dev cycles.
Here's my /etc/lsb-release file:
which looks correct. I thought I'd see what would happen if I ran:
DISTRIB_DESCRIPTION="Ubuntu lucid (development branch)"
This results in a pop-up message saying “An upgrade from 'lucid' to 'karmic' is not supported with this tool”.
sudo update-manager –dist-upgrade
When I close the dialog, I see this message on the terminal:
So something in one (or more) of my files is still pointing to Jaunty. Can someone suggest which one(s) I need to check?
paul@lucid:~$ sudo update-manager --dist-upgrade
ERROR:root:Bad upgrade: 'lucid' != 'jaunty'
Afterthought: actually it's just really saying that the expected upgrade path is from jaunty to karmic, but I still don't know how to fix it! I didn't get any errors the other day when I updated my /etc/apt/sources.list to refer to lucid and did aptitude update/upgrade.