ubuntu-gnome@ubuntu-gnome:~$ sudo fsck.ext2 -p -f -C0 /dev/sda2
Warning! /dev/sda2 is mounted.
fsck.ext2: Bad magic number in super-block while trying to open /dev/sda2
/dev/sda2:
The superblock could not be read or does not describe a valid ext2/ext3/ext4
filesystem. If the device is valid and it really contains an ext2/ext3/ext4
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
e2fsck -b 8193 <device>