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To: freebsd-questions@freebsd.org
Subject: Figuring out why my filesystems spontaneously broke
Date: Wed, 10 Dec 1997 11:13:18 -0600
From: Jeremy Nelson <jnelson@acronet.net>
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I'm not really sure what it is i have gotten myself into, so after searching
the freebsd web site and asking on #freebsd, i thought maybe some of you 
might be able to give me a word of advice or suggestion.

After doing a non-component related hardware maintanance (replaced the 
fan in my power supply), i booted up the machine.  It booted ok, I logged
in, started X windows and pppd.  At an xterm, i 'cd'd into a subdirectory,
and did an 'ls'.  The machine froze for about 15 seconds and rebooted.  

When the machine rebooted, the kernel panic'd because it could not mount
root.  Booting off a floppy yeilded similar results, the root partition 
could indeed not be mounted.  Neither could the /usr partition.

So i move the harddrive to another machine that i know is working ok.
The harddrive appears to have lost its primary superblock.  No problem, i'll
use a backup superblock.  Fsck emits hundreds of DUP and BAD errors, and
a few various errors about "EXCESSIVE DUP BLKS", "INCORRECT BLOCK COUNT",
After making it through pass 1, pass 2 says that a few first-level directories
are empty.  It then dies when it cant find an inode.  Both the / partition
(partition a) and the /usr partition (partition e) have the exact same damage 
signature.

All of the file data is still there ('dd' has no problem finding it on the 
raw devices), and disklabel(8) shows that the disk label is still intact.
Since *both* of the fs's went down and since all the data still seems to 
be there, that would indicate that it wasnt a hardware failure.  Nevertheless,
as someone on #freebsd suggested, my filesystems are toast.

This then is a two part question:
1) Is there any "easy" way to recover the data without having to resort to
   my backups which i have to confess are probably a bit older than they 
   should be?
2) What might have happened?  Is there something i can do to avoid having 
   it happen again?

System specifics:
* 486/66, 40 megs of ram, a Conner CFS1621A IDE drive, generally the rest of
  my system componants are unspectacular (built from parts).  
* FreeBSD 2.2.2 (built from CD sources)  The machine has been in contiuous 
  service since 1994 through a variety of harddrives and systems.  This 
  particular harddrive has been running FreeBSD happily for about 18 months 
  now.  I do not mount my drives async.

Thanks to anyone who might be willing to offer help or suggestions.
Thanks to everyone for their hard work.  I (and lots of others) appreciate it.

Jeremy Nelson