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From: Terry Lambert <terry@lambert.org>
Message-Id: <199605281719.KAA11319@phaeton.artisoft.com>
Subject: Re: Ist there a way to easily reconstruct partition/slice tables?
To: ost@comnets.rwth-aachen.de
Date: Tue, 28 May 1996 10:19:39 -0700 (MST)
Cc: freebsd-questions@freebsd.org
In-Reply-To: <199605280810.KAA23103@smeagol.comnets.rwth-aachen.de> from "Martin Ostermann" at May 28, 96 10:10:36 am
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> last night I cleared the first few blocks on my FreeBSD disk. It had
> nothing particular important on it, which wasn't backup'd, but
> contained some configuration data that would take me a while to
> restore.
> 
> Is it possible to automatically identify the beginning and endings of
> the UFS file systems, and thus construct a new partition table or
> label? It doesn't need to be perfect, just enough to copy the relevant
> information.

In /usr/src/sys/ufs/ffs/fs.h:

#define	FS_MAGIC	0x011954	/* the fast filesystem magic number */

1)	Look for this value (McKusick's birthday 8-)) as a longword value.

At the offset you find the value, minus:

((int)&((struct fs *)0)->d_magic)

You will find the start of the superblock for the FS.

Look at the first one of these minus 8k minus the size of the disklabel
for the start of the partition (assuming reserved space for boot blocks).


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.