Why does a filesystem check fail with a message saying that the superblock cannot be read?

Issue

• Superblock error after upgrading the kernel.
• The following error was observed when rebooting into single user mode.
• Seeing the following error while installing a new kernel and booting from it:

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>

 fsck.ext3: No such file or directory while trying to open /dev/sdb7