Being unable to sleep last night, I decided to update my main operating system (Ubuntu 9.10 Karmic Koala) to Ubuntu 10.04 LTS Lucid Lynx. It started off normally, indicating that it would take several hours to down load I went back to bed. When I got up, it was perfect timing, probably close enough to finishing that I could restart before going to work, when al of a sudden it had a fault. The message was that it was going to restore the original system, then it just hung. After work I tried restarting, since nothing had happened in about nine hours.
It restarted fine, with the new Lucid colours on shut down, only no sign of a desktop when it restarted, just a full screen terminal. Command line is not my area of expertise, in fact I know hardly any of it. I tried a couple of things that seemed logical to me. The terminal had other ideas though, suggesting commands that I could try.
Apparently the problem centred around postgresql-8.4. It seems that the graphical desktop requires this to be working. So I thought maybe removing it, then re-installing might do the trick, you should have seen the list of stuff being deleted on removal. I could see half the operating system disappearing before my eyes.
As a last ditch effort I tried booting into a live CD version of Lucid, in the hope that there would be some kind of disk recovery system on it. The was an application called "disk utility" I tried, but it just said that everything was okay. So I tried rebooting into my Ubuntu partition and guess what? it half worked. I had a random play around, then rebooted again and now I have the updated Ubuntu working.
I have no idea what I did. I think it repaired itself. OSX did it in even more spectacular fashion for me once. I had resigned myself to a fresh install and at the end of it, it asked for my password, then showed a fully restored system, with everything as I had left it. This experience wasn't quite like that, but it was close.