[REPOST] fsck segfaults trying to repair HFS filesystem

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Date: Thu, 24 Jun 2004 18:44:23 +0000 (UTC)

[ I posted this at the beginning of the month. But sadly, I got
   exactly zero replies. I figure, at the risk of being horribly
   redundant, I'll post it one more time, in hopes that somebody
   who has a useful suggestion (or better yet, somebody from HP
   with access to a non-segfaulting fsck!) might have missed it
   the first time around. If not, I guess I'll just give up and
   build a new virgin filesystem on those disks ... ]

Hi, folks ... We have a rather long-in-the-tooth Superdome,
running HP-UX 11.11, and one of its disks (part of a volume
group comprising eight drives) recently developed a bunch of
bad blocks.

The filesystem living on the logical volume isn't backed up.
And of course, we have a couple users who, even though they
were aware (or should have been aware) that there aren't any
backups, are hoping to retrieve their data.

So, my plan was basically this:

(1) Do an image copy of the bad disk onto an identical (but
good) disk. For those sectors which are unreadable, write a
sector of all-zeros.

(2) Replace the bad drive with the good one.

(3) Run fsck on the filesystem (it's HFS; historical reasons
not worth delving into ;-) to resurrect it as much as possible.

Steps (1) and (2) went just fine. Unfortunately, when I try to
repair the moderately-garbled filesystem (several dozen blocks,
which were bad on the original disk, are of course wrong; plus
there are most likely other inconsistencies resulting from the
fact that the hardware problems meant the filesystem didn't get
unmounted cleanly), fsck gets a segmentation fault and drops a
core file.

One would hope that fsck, if confronted with a filesystem that
it couldn't put back together, would at least give up the ghost
more gracefully than _that_.

I'm hoping that there might be some updated fsck kicking around
somewhere, fixing whatever bug is causing it to segfault. But
our friendly HP guy reports that the most recent version he has
access to appears to be identical to the one we have.

Any useful suggestions? Do any HP insiders have access to some
non-standard (and perhaps non-segfaulting) version of fsck that
we could try?

Oh, and I did try using "-f" with "-F hfs" to force a mount even
though the filesystem is dirty. But unfortunately, with things
in this current not-repaired-by-fsck state, only around 1% or so
of the contents can be accessed. (With the filesystem still in
its garbled state, one gets directory read errors on most of the
directories when trying to descend through the hierarchy.)

Many TIA ...

---------------

Mark Bartelt
Center for Advanced Computing Research
California Institute of Technology
Pasadena, California 91125

626 395 2522
626 584 5917 fax
626 628 3994 e-fax

mark@cacr.caltech.edu

http://www.cacr.caltech.edu/~mark

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