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Date: Mon, 5 May 1997 04:22:15 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199705041822.EAA22300@godzilla.zeta.org.au>
To: bde@zeta.org.au, imp@village.org
Subject: Re: Mounting other people's disks?
Cc: hackers@freebsd.org, thorpej@nas.nasa.gov
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

>Umm, the OpenBSD/arc port basically ignores the MBR.  It is
>interesting, yes, but not very interesting to it.  All of the disk
>splitting up is done with respect to the disk label.  Many disks have
>overlapping MBR partitions to deal with the FAT file systems.

Overlapped MBR partitions are invalid.  Be careful running fdisk if you
overlap them.

>: If the `c' partition starts at absolute offset 0, then there are serious
>: problems locating the label.  The label can't always be in absolute sector

>While this is a desirable goal, I don't think that OpenBSD/arc can
>change.  There are too many legacy systems to make it worth while.

Neither can FreeBSD change.  There are too many legacy systems (1.1.5
and 2.0).

>The rules in place for FreeBSD are good ones.  However, I want and
>need a way to short circuit them from time to time.  So far the best
>approach that I've been able to come up with is to have the OpenBSD
>slice take up the entire disk if I need to make it work on FreeBSD at
>any point in the future.

This works best if the OpenBSD slice is the only one on the disk :-).
What does OpenBSD disklabel do if you try to change the `c' partition
to just cover the slice?  I guess it doesn't allow it.  Fudging the
MBR using [Free?]BSD fdisk is easier because there is no error checking
in fdisk.

Bruce