Fixing a MBR (and more) that ??? trashed
Gayn Winters
gayn.winters at bristolsystems.com
Tue Sep 13 12:01:57 PDT 2005
> -----Original Message-----
> From: Alex Zbyslaw [mailto:xfb52 at dial.pipex.com]
> Sent: Tuesday, September 13, 2005 2:06 AM
> To: gayn.winters at bristolsystems.com
> Cc: freebsd-questions at freebsd.org
> Subject: Re: Fixing a MBR (and more) that ??? trashed
>
>
> Gayn Winters wrote:
>
> >Life was good with my dual boot w2k/fbsd system until
> >I wanted to add another disk. The w2k operating
> >system, when booted, saw the new hardware, "installed" it,
> >and demanded that I reboot. OK, but when I did, the
> >FreeBSD boot manager was trashed. Its menu looked like:
> >
> >F1 ???
> >F2 FreeBSD
> >F5
> >Default: F#
> >
> >I could not boot either operating system. In fact the only keys that
did
> >anything were ctrl-alt-del! I removed the new hardware and using
Fixit
> >on the 5.4 release CD, I tried
> > boot0cfg -B ad1
> >This recovered the boot manager, and allowed me to boot w2k, but FBSD
> >wouldn't boot. Pressing F2 in the boot menu still did nothing.
> >
> >
> How far into the disk was FreeBSD? I had a similar problem until I
> specified "-o packet"
> i.e.
> boot0cfg -B -o packet ad1
>
Ah ha! FreeBSD started at cylinder 41610. Looks like I definitely
needed the packet option.
> You could also try writing the boot manager using sysinstall/boot CD:
>
http://www.freebsd.org/cgi/getmsg.cgi?fetch=611111+617364+/usr/local/www
/db/text/2005/freebsd-questions/20050626.freebsd-questions
--Alex
You know, I think I tried that, unsuccessfully. Here are Gary's
thoughts:
> -----Original Message-----
> From: Gary W. Swearingen [mailto:garys at opusnet.com]
> Sent: Tuesday, September 13, 2005 8:03 AM
> To: gayn.winters at bristolsystems.com
> Cc: freebsd-questions at freebsd.org
> Subject: Re: Fixing a MBR (and more) that ??? trashed
>
>
> "Gayn Winters" <gayn.winters at bristolsystems.com> writes:
>
> > 2. Was the disk label on the FreeBSD slice ad1s2 really corrupted?
>
> Unlikely, at least until you ran sysinstall. I've never figured out
> how it handles existing disklabels. Badly, in my limited experience.
> Use "bsdlabel" from a rescue CD and see what you have there. If
> you're concerned about the mount points, mount the "/" device and look
> in /etc/fstab.
>
> > 3. I couldn't get sysinstall to fix this mess - even though I
thought
> > it was fixing the FreeBSD partition mount points and applying a new
BSD
> > Boot Manager. I couldn't get these "fixes" to "commit". Can
sysinstall
> > fix this mess without reinstalling?
>
> I'd use a rescue system -- either CD or another hard disk.
>
> > 4. How do I avoid this situation when I add another disk?
> (Other than trash the w2k partition.)
>
> I don't know about dual-booting MSFT, but you could "dd" the first
> tracks of the HDD and it's primary partitions to files on a formatted
> floppy or two for safe-keeping, before doing anything that could mess
> up the boot records. You might want to save the first track of your
> FreeBSD primary partition too. You can then put them (or selected
> sectors) back with "dd" from most unixy rescue OSes.
Regarding repair:
Alex (above) seemed to think sysinstall would do it,
but I tried a couple times (reloading FreeBSD each time)
and gave up. Given Gary's comments, I suspect that I
corrupted the disk label on the FreeBSD partition mis-using sysinstall
somehow.
I like Gary's idea of a spare copy of the MBR saved on a floppy.
Seems like good insurance.
Regarding avoidance:
I would still like to add additional hard drives to my dual boot
systems.
Is there any safe way to do this?
Thanks!!!
-gayn
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