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Date:      Mon, 4 Dec 2006 10:30:58 +0000
From:      Brian Candler <B.Candler@pobox.com>
To:        freebsd-i386@freebsd.org
Subject:   boot0cfg required before booting >8GB ?
Message-ID:  <20061204103058.GA12800@uk.tiscali.com>

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Hello,

I installed FreeBSD 6.1 on a HP/Compaq i386 machine with two 20GB partitions
- FreeBSD went in the first, and the second was spare. All was well. I let
FreeBSD put its own bootloader in the MBR.

I then installed OpenBSD 4.0 in the second partition. Unfortunately, it was
unable to boot OpenBSD. When the machine started, it offered me

    F1  FreeBSD
    F2  BSD

but when I pressed F2, it just went beep. I mistakenly assumed that this was
a problem with OpenBSD (partly due to an error in their own INSTALL.i386
which still cautions against installing OpenBSD above cylinder 1024)

Anyway, to cut a long story short, I've now been able to solve this problem
simply by reinstalling the FreeBSD MBR, using

    boot0cfg -B -v ad0

and F2 happily boots OpenBSD.

When I ran boot0cfg, it reported that it was using

    options=packet,update,nosetdrv

which is reasonable enough - the boot0cfg manpage says these are the
defaults.

The issue is: why didn't this work first time with the MBR installed during
the FreeBSD installation program?

Unfortunately, I did not take a copy of the MBR before overwriting it with
boot0cfg. But my guess (and it's only a guess) is that at install time the
MBR is being written with options=nopacket

If this is the case, perhaps it ought to be changed to match the current
boot0cfg default, to be able to use modern BIOSes in most machines? Or at
least, could this be noted in the installation documentation?

(My apologies if it already is. A google for "site:www.freebsd.org boot0cfg"
turns up a few pages about boot0cfg, but I could find nothing which
indicates that you may need to re-run boot0cfg after an initial install if
you want the full functionality of booting above the 8GB boundary)

Regards,

Brian.



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