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From: Lee Cremeans <lee@yakko.my.domain>
Message-Id: <199702171623.LAA01016@yakko.my.domain>
Subject: Re: File system/disk recovery tools ?
To: avalon@coombs.anu.edu.au (Darren Reed)
Date: Mon, 17 Feb 1997 11:23:15 -0500 (EST)
Cc: freebsd-hackers@freebsd.org
Reply-To: mcampbel@erols.com
In-Reply-To: <199702171523.HAA21329@freefall.freebsd.org> from "Darren Reed" at Feb 18, 97 02:17:07 am
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> 
> In some mail from Christoph Kukulies, sie said:
> > 
> > > Luigi Rizzo stands accused of saying:
> > > > > dd the whole disk off onto a file and mount it on a vnode?  You might
> > > > 
> > > > unfortunately is 1.6GB ... I need to find a bigger unit!
> > > 
> > > dd bits of it at a time? 8)
> > > 
> > > > > have to reconstruct the label and such, and using fsck's '-b' option
> > > > 
> > > > actually an annoying thing with fsck -b is that I never know what
> > > > to use as an alternate superblock number. 32, says the manpage, is
> > > > an alternate superblock, but what are others ? I guess they depend
> > > > upon the geometry of the disk... is there a "magic" number that I
> > > > can look for ?
> > > 
> > > You mean you didn't write them down when you made your filesystems? 8)
> > > 
> > > Ok, presumably your disklabel is OK.  Have a look in /sys/ufs/ffs/fs.h
> > > at the superblock layout; it's 8K long, has a fixed checksum, and
> > > contains various predictable fields (eg. the last mountpoint).  This
> > > should let you hunt a copy of it down.
> > 
> > Some time ago I wrote a (really quick and dirty) little program which scanned
> > the disk for once existing file systems.
> > 
> > It's too dirty to post in public but if anyone wants it I'll
> > send it. At least one case beside of my own is known to have been
> > successful.
> 
> I've written one of these too (SunOS4) and my comments are the same :-)
> (btw, it worked too :-)
> 
> > Bottomline is that you scan the disk for a FS magic and then with the
> > obtained data (offset and size) you do a dd skip= count= to a file which
> > then can be used as /dev/vn0 to be mounted and files can be restored
> > from there.
> 
> Does dumpfs exist on FreeBSD ?
> 
> 

Yup.  I've used it before.

Lee C.
(and yes, my hostname is bogus...I'm using dynamic IP, and don't want to 
pay for name service :( )