I am trying to debug a hang during shutdown and I don't find where the messages that I see during shutdown are being stored. They aren't in
Your cellphone video camera. Seriously. It's not physically possible for linux to record a log after the "Unmounting local filesystems" message. And for some reason, Ubuntu Oneiric never records any of the shutdown messages, even errors warnings and "[fail]s", at least not anywhere I can find them using
If you have the plymouth splash screen on shutdown that hides the console messages with the Ubuntu logo and progress dots, then hit
ESC to see what's going on behind the curtains... and record it with your video camera for playback later.
Try looking in
sudo find /var/log -type f -print0 | xargs -0 sudo zgrep "the message you are interested in"