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Date: Sun, 24 Dec 1995 00:09:49 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199512231309.AAA23907@godzilla.zeta.org.au>
To: didier@omnix.fr.org, j@uriah.heep.sax.de
Subject: Re: disk to disk copy
Cc: hackers@FreeBSD.ORG
Sender: owner-hackers@FreeBSD.ORG
Precedence: bulk

>> is it to do a disk to disk copy including the partition table and label

>It depends on the device node you're using.  You can copy all, includ-
>ing even the master boot record (which _can_ be the start of the BSD
>disklabel as well, but isn't for most disks).

Actually, overwriting valid MBR's, SecondaryBR's (inside extended
partitions and disk labels should fail.  It succeeds in some cases
because of bugs:
- write protection isn't implemented for MBR's and SBR's
- write protection of labels is implemented but can be defeated by
  copying to the whole disk device (e.g. /dev/rsd0 instead of
  /dev/rsd0c, even when these devices contain the same sectors).

The MBR can never be the start of a FreeBSD disk label, since FreeBSD
labels are always in sector LABELSECTOR = 1.  BSD labels for other
BSD's may start be in sector 0.  FreeBSD would not be able to find
these.

Bruce