Fortunately, the filesystem keeps numerious copies of the superblock on the
disk. You just need to find out where they are! Actually, the locations of
backup superblocks are printed to the screen when the filesystem is created
(not that this helps you now, right). If I remember correctly though,
superblocks are place at regular, predictable places on the parttion. As an
exercise, try creating a filesystem on a floppy drive and watch where the
superblocks are place. On my system I create a 10MB file and the make an
Ext2 filesystem on it and get:
chilin$ dd if=/dev/zero of=fs.bin bs=1024 count=10240
10240+0 records in
10240+0 records out
chilin$ mke2fs fs.bin
mke2fs 1.10, 24-Apr-97 for EXT2 FS 0.5b, 95/08/09
fs.bin is not a block special device.
Proceed anyway? (y,n) y
Linux ext2 filesystem format
Filesystem label=
2560 inodes, 10240 blocks
512 blocks (5.00%) reserved for the super user
First data block=1
Block size=1024 (log=0)
Fragment size=1024 (log=0)
2 block groups
8192 blocks per group, 8192 fragments per group
1280 inodes per group
Superblock backups stored on blocks:
8193
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
chilin$
So, try to run fsck like 'e2fsck -b 8193 /dev/XXX' and see what you get. If
that doesn't net you anything you might try to guess where another
superblock will be. Or, you could try something more drastic. The mke2fs man
page talk about a '-S' option:
-S Write superblock and group descriptors only. This
is useful if all of the superblock and backup
superblocks are corrupted, and a last-ditch recov
ery method is desired. It causes mke2fs to reini
tialize 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 salvageable.
Good luck (from someone else who was trying to bring back a failing disk
from the brink this weekend).
Christopher Judd wrote:
> I'm a relative newcomer to linux (used Amiga's for years). I've
> been running a bo system for about six months. This morning the system
> crashed and will not boot from the hard disk. I booted from the rescue
> disk but cannot mount /hda3 (/hda1=w95, /hda2=swap). e2ckfs reports a
> bad superblock. Is there a way to create a new superblock so that I can
> mount this drive?
>
> -Chris
>
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