Fixing a MBR (and more) that ??? trashed

Gayn Winters gayn.winters at bristolsystems.com
Mon Sep 12 22:12:55 PDT 2005


I recently installed Windows 2000 and FreeBSD 5.4 on an old HP Pavilion
XG836.  [The FreeBSD installation was a breeze (Kudos to the FBSD
hardware team), while w2k was a disaster!  But, that's another story...]
For reasons of space and cabling (it is a very small box) I put the CD
as the master and the HDD as the slave on a single IDE cable so that the
HDD was ad1.  I dual booted using the FreeBSD Boot Manager.

Life was good 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.

Fdisk indicated that the two slices were ok, and the disklabel in
sysinstall showed that the partitions in ad1s2 were fine, but the
mounting information was apparently gone.  If I went into Fixit,
disklabel (bsdlabel) indicated that the label on ad1s2 was bad.  I was a
little surprised, since I assumed (perhaps incorrectly) that all the
corruption that w2k caused was in the Master Boot Record. I tried fixing
it with the disklabel in sysinstall without luck.  Back in Fixit mode, I
could execute bsdlabel -w ad1s2, I couldn't get bsdlabel -e ad1s2 to
work since I couldn't get an editor to run.  EDITOR was /mnt/stand/vi,
which didn't work and blanking EDITOR didn't work either.  Reinstalling
FreeBSD brought everything back.

Questions:
1.  What did/do I need to do to completely fix the Master Boot Record?
(Short of reinstalling FreeBSD!)
2.  Was the disk label on the FreeBSD slice ad1s2 really corrupted?  If
so, I tend to doubt that w2k did it; hence, the culprit would be ... me!
What did I do?
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?
4.  How do I avoid this situation when I add another disk? (Other than
trash the w2k partition.)

TIA,

-gayn







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