From owner-freebsd-stable  Fri Aug  4 10:58:18 2000
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Date: Fri, 4 Aug 2000 10:58:14 -0700 (PDT)
From: David Wolfskill <dhw@whistle.com>
Message-Id: <200008041758.KAA46023@pau-amma.whistle.com>
To: freebsd-stable@freebsd.org
Subject: boot0 problem on FreeBSD 4.1-{RELEASE,STABLE}
Cc: ambrisko@whistle.com, jhb@freebsd.org, julian@freebsd.org
Sender: owner-freebsd-stable@FreeBSD.ORG
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Sorry I wasn't in a position to test this earlier, but the evidence
at hand indicates that the 1024-byte boot0 (as of 4.1-R); boot0.s
1.14.2.2) is failing for the machines we have been deploying for the last
couple of weeks for our engineers.  (I had deployed all of them so far
running 4.0-R; I was testing 4.1-S, since it had been working OK for me
on a couple of laptops, and apparently for a couple of these machines,
as well.)

The machines are IBM Intellistation M Pro Type 6868 with 128 MB RAM;
the failure was found on a dual-CPU (P3) 733MHz box.

To verify the failure, I loaded 4.1-R from a local mirror of the release
(from freebsd.org), specifying that the FreeBSD bootmanager should be
installed (in order to be able to select between either of a couple of
boot partitions).

An attempt to boot the resulting system results in an apparent "hang"
(with the status code in the upper right-hand corner of the screen
reading "7F", if the "Power On Status" option is selected at the BIOS
level).  There is no "menu" of boot partitions to select, and the hang
appears to require a power-cycle to break.

I was able to "un-break" the system (after doing the above) by booting
from the 4.1-R floppies, selecting "Fixit", assigning an IP address to
the box via ifconfig, using FTP to copy a 512-byte boot0 from another
machine's /boot/boot0, then

	fdisk -B -b ./boot0 ad0

("./boot0" being the copy of boot0 I had brought over via FTP.)


A subsequent re-boot brought up the familiar boot0 partition-selection
menu (and selecting F2, for the FreeBSD partition, booted normally).


I have motivation to assist in debugging the problem (some 20+ more
machines to load).  :-}  (I have a circumvention available -- involving
forcing the use of the old boot0 -- but this isn't a long-term option,
by any means.)

Please note:  this can create a "silent failure" of a rather insidious
kind:  One might start with a 4.0 system (and thus, the 512-byte boot0),
and through various upgrades, be running 4.1-S or even 5.x-C, and all
will be Just Fine... until the new boot0 is actually written to sector
0, at which point, you're in a singularly awkward position at next
reboot.

So:  how can I help fix this?

Thanks,
david
-- 
David Wolfskill		dhw@whistle.com		UNIX System Administrator
voice: 650/577-7158	TIE: 8/499-7158		FAX: 650/372-5915


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