Re: Determine is filesystem is Etx2 or Ext3 or Ext4?
'blkid', 'mount', 'cat /proc/mounts' are all good ways
Another is 'cd /proc/fs' or 'cd /sys/fs' and look around (the devices will be listed under the filesystem type).
'tune2fs -l <device>' is the best way to tell absolutely. It will tell you the filesystem magic number. Unfortunately, then you've got to figure out what filesystem that corresponds to. (This is how the system actually knows what filesystem it is. However, you can also tell by glancing at the filesystem features.
Favorite man page quote: "The backreference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regular expression." [excerpt from grep(1)]