Some time ago I rebooted my Ubuntu file server, and noticed that it was taking forever to reboot. It’s usually headless, so I hooked up a spare monitor and saw a message that I didn’t expect:
“A start job is running for Create Volatile Files and Directories”
So that’s one I’d never seen before, so went straight to the Googles, and found this lovely explanation: http://deshack.net/debian-hangs-during-boot/
So it turns out that a bug in “system-config-printer” of all things, causes extremely bloat in /tmp, causing a huge number of files to be created over time, and this essentially puts the system in a hung state.
The fix, as mentioned on the website above, is quite straightforward. Once you boot into single user mode (see the link for details), you can do the following:
rm -rf /tmp
chmod 1777 /tmp
This resolved the issue for me immediately, and hopefully you too!