A superblock is a record of the characteristics of a filesystem, including its size, the block size, the empty and the filled blocks and their respective counts, the size and location of the inode tables, the disk block map and usage information, and the size of the block groups.If you have a bad superblock so you can’t mount your ext2/ext3 partition, you can still mount partition using backup copies of your superblock.
These superblock copies live at the locations: 32768, 98304, 163840, 229376, 294912 … It is dependent on the block size.
You can run
e2fsck as follow and if it is ok, original superblock at address 0 will be re-created:
e2fsck -b 163840 /dev/sda2