Date: Tue, 5 Dec 2006 08:19:44 +0100 From: Remko Lodder <remko@elvandar.org> To: Brian Candler <B.Candler@pobox.com> Cc: Remko Lodder <remko@FreeBSD.org>, freebsd-i386@FreeBSD.org Subject: Re: i386/70525: [boot] boot0cfg: -o packet not effective Message-ID: <20061205071944.GF12800@elvandar.org> In-Reply-To: <20061204194709.GA7663@uk.tiscali.com> References: <200612041130.kB4BUKst050264@freefall.freebsd.org> <45746B08.6070705@FreeBSD.org> <20061204194709.GA7663@uk.tiscali.com>
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On Mon, Dec 04, 2006 at 07:47:09PM +0000, Brian Candler wrote:
Hello Brian,
> Are you saying that the FreeBSD MBR can only boot operating systems which
> were installed at the time that the MBR was installed?
No I am not stating that, I was just theorising there, I am not aware on
the internals of the MBR, but I could imagine that it can only boot systems
that have been installed (since then there is information about the operating
system and the boot 'sector' on the partition, prior to that
it is unfilled and the system cannot tell whether it is going
to be used to boot or not.
>
> I don't think this is the case, because the MBR correctly detected both
> partitions, and offered them to me:
Well, are you sure that the F2 here implies the same partition?
>
> F1 FreeBSD
> F2 BSD
>
> So it knows that ad0s2 exists, it knows that ad0s2 is bootable, and it even
> knows what type of O/S is in that partition (presumably from the type code,
> A6)
>
> However, pressing F2 fails.
Yes, well are we sure that F2 matches your OpenBSD installation and is not some
kind of first partition check or something? I do not know how to verify this
sadly :(
>
> All it has to do is to load the boot sector from that partition, and jump to
> it. I'm presuming that this requires the new 'packet' BIOS call when this
> sector is located above the 1024-cylinder mark.
Imo all you need to do is add the new partition to the mbr bootblock and it will
start. I am not sure whether you want to have all partitions listed from which
you can potentially boot even when there is nothing available there yet
(which probably is if you do this manually).
Perhaps we need someone with more MBR foo then me ;-)
Thanks for the discussion though, it gives me more insight in how this works
and hopefully it helps you as well!
>
> Regards,
>
> Brian.
--
Kind regards,
Remko Lodder ** remko@elvandar.org
FreeBSD ** remko@FreeBSD.org
/* Quis custodiet ipsos custodes */
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