HELP: BAD SUPER BLOCK: MAGIC NUMBER WRONG

HELP: BAD SUPER BLOCK: MAGIC NUMBER WRONG

Post by Tom G. Pool » Sat, 01 Aug 1998 04:00:00



Any ideas of how to gain access to this disk?  I receive the following
error message:

Quote:> Alternate super block location: 1266272.
> ** /dev/rdsk/c0t4d0s5
> BAD SUPER BLOCK: MAGIC NUMBER WRONG
> USE AN ALTERNATE SUPER-BLOCK TO SUPPLY NEEDED INFORMATION;
> eg. fsck [-F ufs] -o b=# [special ...]
> where # is the alternate super block. SEE fsck_ufs(1M).

from "fsck -y -o b=$alt_super_block /dev/rdsk/c0t4d0s5"

where $alt_super_block equals every listed superblock.

I've tried the following:

1) All superblocks (found w/nfs -Nv ...)
2) Power cycled disk
3) Shut down all power
4) Open unit and tapped, and I can hear it spin-up & see disk access
light

Any ideas are appreciated---please email responses and I'll consolidate
with a final post to this string.

Regards,


 
 
 

HELP: BAD SUPER BLOCK: MAGIC NUMBER WRONG

Post by rg.. » Sat, 01 Aug 1998 04:00:00



: Any ideas of how to gain access to this disk?  I receive the following
: error message:

:> Alternate super block location: 1266272.
:> ** /dev/rdsk/c0t4d0s5
:> BAD SUPER BLOCK: MAGIC NUMBER WRONG
:> USE AN ALTERNATE SUPER-BLOCK TO SUPPLY NEEDED INFORMATION;
:> eg. fsck [-F ufs] -o b=# [special ...]
:> where # is the alternate super block. SEE fsck_ufs(1M).
:>

: from "fsck -y -o b=$alt_super_block /dev/rdsk/c0t4d0s5"

: where $alt_super_block equals every listed superblock.

: I've tried the following:

: 1) All superblocks (found w/nfs -Nv ...)
: 2) Power cycled disk
: 3) Shut down all power
: 4) Open unit and tapped, and I can hear it spin-up & see disk access
: light

: Any ideas are appreciated---please email responses and I'll consolidate
: with a final post to this string.

: Regards,


These kind of superblock corruptions are very hard to fix. Most of the time
the alternate superblocks are also corrupted in the same way.

Also check the partition table/VTOC using format & prtvtoc, just in case.

If you've backups, then just go the newfs/restore way.

Hope it helps,

-Raman

 
 
 

1. functioning file system with "bad super block: magic number wrong"?

Re-installed 4.8 after formatting the disk. Just as a test, went down
to single-user mode, un-mounted all the file systems, and ran fsck
which reported no problems. For curiosity, I ran fsck -p /dev/ad0. It
reported that there was a "bad super block: magic number wrong" and
unexpected inconsistency: run fsck manually.

This message was ignored and the system was rebooted with no problems.
A new kernel was built and no problems occurred. It seems that the
file system is working perfectly well, in spite of this "bad super
block".

The question is, is it normal to have some trivial errors be reported
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