The Karmic upgrade went really well but MySQL server seemed to die along the way. A temporary solution that worked for me was found here – http://ubuntuforums.org/showthread.php?t=1040786.
sudo apt-get remove --purge mysql-server-5.1
sudo apt-get autoremove
sudo rm -rf /etc/mysql
sudo apt-get install mysql-server-5.1
[update] This solution doesn’t persist after reboot (at present). Still useful if I need to test MySQL but not a proper answer.
sudo /etc/init.d/mysql start
does the trick. Not sure why it isn’t happening automatically on startup.
The mysql file was in /etc/rc3/, rc4, and rc5, but not rc2. Why? No idea at all. Anyway, a quick gksu nautilus and copying S19mysql (yours may have a different number) and pasting it from rc3 into rc2 later, then a reboot to be sure. Working as needed. NB a prefix of K means deactivate.
To see if mysql is running:
ps -ef | grep mysql
a single line response (your mysql client?) is not a good sign.
Here is on thread of interest: http://ubuntuforums.org/showthread.php?p=8320705
Here are the main resources I found useful:
NB My AppArmor mask denied etc didn’t affect the working of the system so was a bit of a side-track in my case. Mainly affects you if you don’t use standard path locations.