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From: Mikhail Teterin <mi@video-collage.com>
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Subject: Re: recovering disk
In-Reply-To: <199808261850.UAA19508@semyam.dinoco.de> from Stefan Eggers at "Aug 26, 98 08:50:44 pm"
To: seggers@semyam.dinoco.de (Stefan Eggers)
Date: Wed, 26 Aug 1998 15:22:37 -0400 (EDT)
Cc: current@FreeBSD.ORG
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Stefan Eggers once stated:

=Thus I wrote a small programm which opened the slice and read every 8
=KByte block (the block size of the filesystem's used) and checked them
=for being a superblock. I did the same for the cylinder group headers
=next to them.

So, the first backup superblock is right next to the main one?
Ok. The disk was mounted at the time of the crash. Would not the
super blocks differ?

=This is trivial to do. The comments in /usr/include/ufs/ffs/fs.h
=should lead the way the the right information in there with a little
=bit of understanding how the filesystem is organized.

[...]

=I think one can do this with a program quite easily but I had neither
=time for debugging one nor did I want to trust any on this. Needless to
=say there were no current backup of the filesystems so a program giving
=bad numbers would have been fatal.

So, how did you get it back?

=> 	3) write it out (all the way to the end) as a separate file, which
=
=Given you have the start and the probably size dd will do the rest if
=used on the slice.

Indeed...

=> 	4) vn-mechanism will let me access and get to my files
=> ?
=
=Left as an exercise to the reader.  I'd expect that to work w/o any
=surprises.

=> I'm quite sure my data is intact on the disk and it is only its
=>beginning tha t's hosed. Thanks in advance for your ideas and
=>suggestions. Yours,

=If the start including first superblock is damaged you'll of course
=have to use fsck with one of the many alternative superblocks whose
=position you get if you do it the way I recovered the disklabel or
=have noted when you newfs'ed the filesystem.

Yes... Still, any chance I can re-create the partition table (with
fdisk) and disklabel?

Thanks a lot!

	-mi

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