I'm running fsck and getting "ext2fs_open2: Bad magic number in super-block"

Question

I'm running:

fsck -n /dev/sdb2

and I'm getting:

fsck from util-linux 2.31.1
e2fsck 1.44.1 (24-Mar-2018)
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/sdb2

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>
 or
    e2fsck -b 32768 <device>

Any advice? What's wrong with the partition and what should I do about it??

Additional information, as requested:

sudo fdisk -l

outputs:

Device        Start      End  Sectors  Size Type
/dev/sdb1  32335872 60061695 27725824 13.2G Microsoft basic data
/dev/sdb2      2048     4095     2048    1M BIOS boot
/dev/sdb3      4096   503807   499712  244M EFI System
/dev/sdb4    503808  4610047  4106240    2G Linux filesystem
/dev/sdb5   4610048 32335871 27725824 13.2G Linux filesystem

Solution

You're doing the fsck on the wrong partition (sdb2).

sudo fdisk -l shows us that the following partitions are "Linux filesystem"...

/dev/sdb4    503808  4610047  4106240    2G Linux filesystem
/dev/sdb5   4610048 32335871 27725824 13.2G Linux filesystem

Here are the commands that you should be using...

Boot to Ubuntu Live DVD/USB in "Try Ubuntu" mode.

Open the terminal application and type:

sudo fsck -f /dev/sdb4
sudo fsck -f /dev/sdb5
reboot