root@rescue:/# fsck /dev/sda1
fsck from util-linux 2.20.1
e2fsck 1.42.5 (29-Jul-2012)
ext2fs_open2: Bad magic number in super-block
fsck.ext2: Superblock invalid, trying backup blocks...
fsck.ext2: Bad magic number in super-block while trying to open /dev/sda1

The superblock could not be read or does not describe a correct ext2
filesystem.  If the device is valid and it really contains an ext2
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>


root@rescue:/# fsck /dev/sda3
fsck from util-linux 2.20.1
e2fsck 1.42.5 (29-Jul-2012)
/dev/sda3: clean, 837/120782848 files, 13216202/483126528 blocks


root@rescue:/# fsck /dev/sda2
fsck from util-linux 2.20.1
e2fsck 1.42.5 (29-Jul-2012)
/dev/sda2: clean, 90016/1281120 files, 882203/5119744 blocks