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Date:      Fri, 21 Jul 2000 18:58:05 +1000 (EST)
From:      Bruce Evans <bde@zeta.org.au>
To:        John Baldwin <jhb@pike.osd.bsdi.com>
Cc:        Warner Losh <imp@village.org>, dwhite@resnet.uoregon.edu, freebsd-current@FreeBSD.ORG
Subject:   Re: No /boot/loader
Message-ID:  <Pine.BSF.4.21.0007211852440.2315-100000@besplex.bde.org>
In-Reply-To: <200007210653.XAA42478@pike.osd.bsdi.com>

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On Thu, 20 Jul 2000, John Baldwin wrote:

> No, that's wrong, too.  A normal disk has a proper slice table (slices start
> on cylinder boundaries and do not contain the MBR, thus leaving the first
     track
> cylinder unused).  A truly dedicated disk (disklabel auto <foo>) uses a
  track
> ...
> at all to the drive's geometry.  As with truly dedicated mode, the MBR is
> actually contained in boot1, but in dangerously dedicated mode we use the
> slice table hard-coded into the boot code.  This slice table has 1 slice
> which is 50000 blocks long, or 25000k.  The rest of the disk is marked as
> unused even though it is, in fact, used.  The fact that it works at all is
> due to brokenness on our part (we don't check that partitions in a disklabel
> fit in the parent slice) and also results in several hacks in various portions
> of the code where we have to check for such bogusness and work around it.

No, that's wrong too :-) .  We a lot of checking that partitions in a
disklabel fit in the parent slice.  We clip partitions that don't fit in
various ways for backwards compatibility.

Bruce



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