"Cannot find file system superblock" error - how to recover?

[Scott I. Remick]

--- Sergey 'DoubleF' Zaharchenko <doublef at tele-kom.ru> wrote:
> Oh yes there are... what's surprising? If you are sure that the problem
> is with the superblock, pick any you wish.
> 
> The actual number of superblock copies depends on the disk size and the
> parameters you give to newfs.

[...]

> It's about THE superblock, not a superblock copy. There can be only one
> superblock. There may be many copies. But if you dd them to the
> superblock, that'll be fine.

Ahh ok, I've learned something new. Guess I misinterpreted the information I
found online. I'm not complaining: this is GOOD news. :)

> BTW, what's the output of ``disklabel -r /dev/ad6s1c'' ?

su-2.05b# disklabel -r /dev/ad6s1c
# /dev/ad6s1c:
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  c: 156344517       63    unused        0     0         # "raw" part, don't
edit
  e: 156344517       63    4.2BSD     2048 16384    89
partition c: partition extends past end of unit
disklabel: partition c doesn't start at 0!
disklabel: An incorrect partition c may cause problems for standard system
utilities
partition e: partition extends past end of unit

That doesn't look good.

By the way, the past posts I've read suggest that even if I use fsck_ffs -b
to run fsck with a diff superblock (say, the one at 160) that it doesn't
actually fix the master copy, and that I still need to use dd to fix the
original. The command I've seen used is:

dd if=/dev/ad6s1c skip=32 of=/dev/ad6s1c seek=16 bs=512 count=16

1) Do I just replace the 32 of "skip=32" with 160 (or whichever superblock
makes fsck_ffs -b happy)?

2) I've also read that the size and location of the original superblock can
vary. Do I have to modify the seek/bs/count values to account for this? And
if so, how do I find the proper values?

Nothing done yet... don't wanna screw this up. Thanks everyone!

=====
Scott I. Remick   --==--   ICQ: 450152 
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