Date: Sat, 22 Jan 2011 22:22:01 -0600 (CST) From: Scott Bennett <bennett@cs.niu.edu> To: freebsd-questions@freebsd.org Subject: Re: help requested in fixing disk label mistake Message-ID: <201101230422.p0N4M14G012454@mp.cs.niu.edu>
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I just wrote:
> A couple of days ago, I reorganized the internal hard drive of my machine
>to reclaim space that used to be occupied by another operating system for use
>with my now exclusively FreeBSD system. I used a stand-alone partition manager
>to edit the slices down to just two slices. I then attempted to bsdlabel the
>first slice, but made a bit of a slip. When I should have typed
>
> bsdlabel -w ad0s1
>
>I actually typed
>
> bsdlabel -w da0s1
>
>Oops.
> I went ahead with the work on the internal drive (ad0), and the system
>is up and running fine. Now I'd like to try to fix the damage done to the
>external drive that I relabeled by mistake. That drive's layout before the
>damage was done was a single slice, divided into two partitions (da0s1 and
^^^^^
>da0s2), each of which was then glabel'ed. The moment I rewrote the bsdlabel
^^^^^
Yet another pair of mistakes on my part. Those should have said da0s1d
and da0s1e. Sorry for any confusion.
>for the first slice by mistake, the two partitions' entries in /dev/label
>vanished, of course. I checked and discovered that the only external drive
>for which I had not kept backup copies of the bsdlabel information was that
>drive. :-( Fortunately, the full backups of the file systems that I needed
>to reload onto the internal drive were in the first partition of the external
>drive in question (used to be s1d, now s1a for the time being), so by mounting
>/dev/da0s1a I still had full access to the file system containing the backups.
> My hypothesis is if I can somehow rewrite a correct bsdlabel for the
>affected slice, that the system will then recognize the glabel metadata for
>the two partitions immediately, and the /dev/label entries will appear right
>away like magic. Unfortunately, without a backup file of the bsdlabel
>information, I'm unsure how to accomplish that. Is there some way that I can
>discover the exact size in sectors of the first partition, so that I could
>edit the bsdlabel information and redefine it as two partitions of the correct
>sizes and offsets? Is there some field in dumpfs(8) output that would give me
>what I need (allowing, of course, for the fact that the first partition
>is actually one sector longer than anything dumpfs(8) would know about due to
>the glabel metadata in the final sector of the partition)? Or is my hypothesis
>stated above actually incorrect, and if so, why/how?
> PLEASE send any replies to ME DIRECTLY (or at least Cc: me directly)
>because I receive this list in digest form and am at least a week and a half
>behind on my reading. :-} Thanks much in advance for any helpful ideas.
Scott Bennett, Comm. ASMELG, CFIAG
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