*BSD News Article 90798


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From: Jim Durham <durham@w2xo.pgh.pa.us>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Help needed - freeBSD crashed, won't boot at all!
Date: Mon, 10 Mar 1997 22:12:19 -0500
Organization: Dis-
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Message-ID: <3324CD93.59E2B600@w2xo.pgh.pa.us>
References: <33234701.C07@xnet.com>
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To: Paul Young <phy@xnet.com>
Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:36879

Paul Young wrote:
> 
> My freeBSD box (2.1.6.1) crashed while I was trying to back it
> up. I don't know why or how, but I get this message when it tries
> to reboot:
> 
> > WARNING: / was not properly dismounted.
> > swapon: adding /dev/sd0s1b as swap device
> > Automatic reboot in progress...
> > /dev/rsd0a: /dev/rsd0a: BAD SUPER BLOCK: VALUES IN SUPER BLOCK DISAGREE WITH THOSE IN FIRST ALTERNATE
> >
> > /dev/rds0a: UNEXPECTED INCONSTENCY: RUNfsck MANUALLY.
> > Automatic file system check failed... help!
> > ...
> 
> When I fsck manually, I get:
> 
> > # fsck
> > ** /dev/rsd0a
> > BAD SUPER BLOCK: VALUES IN SUPER BLOCK DISAGREE WITH THOSE IN FIRST ALTERNATE
> > pid 16 (fsck), uid 0: exited on signal 8
> > Floating exception
> 
> Can someone help me recover the disk? I have a lot of stuff on it
> that I need - this was during my first full backup!
> While I'm at it, how do I get the system to do a crash dump? It
> had crashed a couple of times doing a compile before.
> 
I'll try, although I'm no guru, but no one else seems to have
answered you.
My guess is, having done this at least once to myself, that you
somehow entered the backup command incorrectly and ended up writing
*to* your raw disk instead of *from* it to the backup media. This
is a common "whoops" and causes the front end of the disk to be
overwritten until it just crashes. This is why your first superblock
is bad.
You need to run fsck -b 32. The first alternate superblock is at
block 32. If it's wrong also, it may damage your disk further, so
be careful, in fact.....
if you can boot the system from a boot floppy, then use the
fixit floppy and dd the whole drive out to tape. This way
at least you will have the valuable data preserved in case
it screws up when you do fsck -b  32 .

dd if=/dev/rsd0a of=/dev/XXX   (XXX being whatever your tape is, st0?)
If it won't fit on one tape..you may have to break it up in pieces.

Good Luck,

Jim Durham