Subject: Big boo-boo (big bug?)
To: None <>
From: Drew Hess <dhess@CS.Stanford.EDU>
List: current-users
Date: 01/26/1994 00:56:56
Tonight after doing a complete recompile and kernel rebuild from the Jan 25
sources, I foolishly decided to update my bootblocks.  After checking to make
sure my disktab entries were correct, I did the following:

disklabel -w -r wd0 wdac2340
disklabel -w -r sd0 cp30540

where "wdac2340" and "cp30540" are my WD 340MB IDE drive and Conner 540MB SCSI
drive, respectively.  I then halted the system and rebooted.

When OS-BS 1.35, my bootmanager, came up, I chose the NetBSD option, and the
machine proceeded to hard reset and reboot, cycling back thru the memory POST.
Same thing the second time.

"Uh, oh...."

I booted into DOS, which is working fine, did an FDISK /MBR to remove OS-BS
from the bootrecord on the IDE drive, set the active partition to 4 (my NetBSD
root partition on the IDE drive, which I use to boot my system -- the rest
of NetBSD resides on the SCSI drive), and rebooted.  The machine just started 
cycling thru reboots again, as I expected.

Luckily I have a "backup" root partition on the SCSI drive, which I only use
to boot from in emergencies just like this one.  I went into CMOS setup,
disabled the IDE drive, and rebooted; same thing, endless hard resets and
reboots.  (In retrospect, it was incredibly stupid of me to mess with *both*
bootblocks at once, instead of keeping one around for a backup.  In fact,
it was probably stupid to play with the bootblocks period.)

So, does anyone have any suggestions as to how I can recover?  Can't boot
into single-user mode because I don't even get the NetBSD boot prompt; the
machine just resets as soon as I try to boot off the NetBSD partition.  Is
there someway to use the NetBSD-0.9 kernel floppy to put old bootblocks on
my drives?  Is there some way to force working bootblocks onto my drives?

I just got a tape drive a few weeks ago and made a complete system backup
about a week ago, but I'd rather not revert to that if I can avoid it
(didn't back up the source tree, for one thing).

Are the most recent bootblocks known to work on either IDE or SCSI drives?
It's quite possible that I just did something wrong, but I'm sure the disktabs
were OK.  

My old (working) bootblocks were version 1.12, at least the IDE blocks were;
don't know about the SCSI drive.

Any and all help would be *much* appreciated.