When did I last run FSCK?

aka ‘how long has it been since I ran fsck?’

Answer: run ‘tune2fs -l <device>’ and look at

Mount count: 2
Maximum mount count: 36
Last checked: Tue Sep 6 23:12:36 2011
Check interval: 15552000 (6 months)
Next check after: Sun Mar 4 23:12:36 2012

If the mount count = max mount count, you’re due for an FSCK.  If you’re booting after the ‘Check interval’, (which is helpfully calculated for you on the ‘Next check after:’ line), you’re due for an FSCK.

Knowing if your scheduled reboot will take several hours in order to run the FSCK?  Priceless.