-b 8193 is from 1,44MB floppy disk drives times. If mkfs.ext2-4 is called without any inode or block or superblock parameters, the first backup of the superblock is written to -b 32768.is corrupt, and you might try running e2fsck with an alternate superblock:
e2fsck -b 8193 <device>
# e2fsck -b 8193 /dev/sdb1
e2fsck 1.41.14 (22-Dec-2010)
e2fsck: Bad magic number in super-block while trying to open /dev/sdb1
To determine the backup superblocks you can use
Code: Select all
dumpe2fs /dev/sdaX | grep -i backup
bash-3.00# dumpe2fs /dev/sda2 | grep -i backup
dumpe2fs 1.41.11 (14-Mar-2010)
Journal backup: inode blocks
Backup superblock at 32768, Group descriptors at 32769-32771
Backup superblock at 98304, Group descriptors at 98305-98307
Backup superblock at 163840, Group descriptors at 163841-163843
Backup superblock at 229376, Group descriptors at 229377-229379
Backup superblock at 294912, Group descriptors at 294913-294915
Backup superblock at 819200, Group descriptors at 819201-819203
Backup superblock at 884736, Group descriptors at 884737-884739
Backup superblock at 1605632, Group descriptors at 1605633-1605635
Backup superblock at 2654208, Group descriptors at 2654209-2654211
Backup superblock at 4096000, Group descriptors at 4096001-4096003
Backup superblock at 7962624, Group descriptors at 7962625-7962627
Backup superblock at 11239424, Group descriptors at 11239425-11239427
man mke2fs :
-S Write superblock and group descriptors only. This is useful if
all of the superblock and backup superblocks are corrupted, and
a last-ditch recovery method is desired. It causes mke2fs to
reinitialize the superblock and group descriptors, while not
touching the inode table and the block and inode bitmaps. The
e2fsck program should be run immediately after this option is
used, and there is no guarantee that any data will be salvage-
able. It is critical to specify the correct filesystem block-
size when using this option, or there is no chance of recovery.