Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ukma!uflorida!mephisto!utkcs2!alphard!battle
From: battle@alphard.cs.utk.edu (David Battle)
Newsgroups: comp.unix.wizards
Subject: Re: Trashed partition table on a Trimarchi Datastaion 600 disk
Keywords: partition table DECStation 3100 Trimarchi
Message-ID: <1485@utkcs2.cs.utk.edu>
Date: 6 Dec 89 21:14:41 GMT
References: <1483@utkcs2.cs.utk.edu>
Sender: news@utkcs2.cs.utk.edu
Reply-To: battle@alphard.cs.utk.edu (David Battle)
Organization: CS Dept -- University of TN, Knoxville
Lines: 35

In article <1483@utkcs2.cs.utk.edu> battle@alphard.cs.utk.edu (David Battle) writes:
>We have a Trimarchi Datastaion 600 disk with a botched partition table.
>It is mounted on a DECStation 3100.
>
>I have reason to believe that the data on the various partitions may still
>be valid, but it's hard to be sure without a correct partition table.
>
>Does anyone know any way (simple or arcane) to recover the partition table
>on a disk such as this?
>
>						-David L. Battle
>						battle@battle.esd.ornl.gov
>						battle@utkux1.utk.edu

Well, I answered my own question this time.  The answer is "yes it can be
done" because I just did it.  Basicly what I did was tried to remember how
I had parititioned it, then tried various guesses by using chpt followed
by fsck -n on the partition whose bounds I was guessing (the -n flag makes
sure fsck doesn't try to write on the partition if it isn't right).  It only
took a few tries before I had guessed the first partition, and it went pretty
smoothly from there because all of the partitions were contiguous (and a
couple of them (I remembered) were the exact same size).

The problem appears to have been that the "b" partition started at the very
beginning of the disk (the "a" partition was 0 length) but the partition table
is normally stored at the beginning of the "a" partition (isn't it?).  Thus we
had no problems until we decided to make that particular "b" partition an
alternate swap partition.  Once we started swapping on "b", everything was
*still* hunky dory until I rebooted and tried to remount the other partitions
on that disk.  Only then did the file system notice that the partition table
was missing (it had been over written by swapping activity).

                                                -David L. Battle
                                                battle@battle.esd.ornl.gov
                                                battle@utkux1.utk.edu