Corrupt File System (was Re: Unmountable disk partitions)

[Jonathan Groves]

In article <1990Nov15.204556.12303 at scuzzy.in-berlin.de> src at scuzzy.in-berlin.de (Heiko Blume) writes:
[Deleted stuff on Unmountable disk partitions]
> i'll be happy to send you a little superblock editor (:-)
> so you can change the filesystem type magic number 
> or whatever you like to make mount fail.

I may need such an editor.

Today one of our file servers crashed [Ultrix] and
when it tried to come back up, it failed during the fsck.

After an interactive session with fsck, the disk still
failed, and another interactive fsck leaves me with this:
(Comments from M.K.McKusick's FSCK document (1983),
 included with Ultrix Supplementary Docs. Volume 3)

** /dev/ra0f
** Last Mounted on /usr/users
** Phase 1 - Check Blocks and Sizes
CG 0: BAD MAGIC NUMBER
1763713056 BAD I=28
[Several of these]
1601463663 BAD I=28
EXCESSIVE BAD BLKS I=28
CONTINUE? y

# CG c: BAD MAGIC NUMBER
# The magic number of cylinder group c is wrong.
# This usually indicates that the cylinder group maps have
# been destroyed.  When running manually the cylinder group
# is marked as needing to be reconstructed.

? How is the map reconstructed, and at what phase of fsck?
? Obviously after where it dies on me.
? Is this happening because I "corrected" part of the
? file system that I shouldn't have?

** Phase 2 - Check Pathnames
ROOT INODE UNALLOCATED. TERMINATING.

# ROOT INODE UNALLOCATED. TERMINATING.
# The root node (usually inode number 2) has no allocate mode bits.
# This should never happen.  The program will terminate.

? So what do I do? 
? I newfs/mkfs and restore from backups...
? Is there any way I could have "repaired" the disk using
? some kind of file system binary editor (fsdb?)?
? Where would I find such an editor?
? Where would I find info on where info is stored on
? the disk and in what format?

In several places the document concludes the solution to be
"See a guru."  But there's no guru index.  :-)

I hope someone out there can answer these questions...

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