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Date:      Mon, 18 Dec 2006 15:28:30 +0100
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        RW <fbsd06@mlists.homeunix.com>
Cc:        freebsd-geom@freebsd.org
Subject:   Re: gconcat/gbde  DVD encryption problem
Message-ID:  <20061218142830.GE73800@garage.freebsd.pl>
In-Reply-To: <200612181322.13560.fbsd06@mlists.homeunix.com>
References:  <200612181322.13560.fbsd06@mlists.homeunix.com>

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On Mon, Dec 18, 2006 at 01:22:13PM +0000, RW wrote:
> A couple of years ago, I created some DVDs encrypted with gdbe. I used 2=
=20
> concatenated,  file-backed md devices (to avoid the 2GB dvd file limit) a=
nd=20
> burned them to dvd. The resulting DVD was accessed like this:
>=20
> ----------------------------------------------------------
> mount  /dvdrw
>=20
> mdconfig -a -t vnode -f /dvdrw/d1 -u 31
> mdconfig -a -t vnode -f /dvdrw/d2 -u 32
>=20
> gconcat create datadvd /dev/md31 /dev/md32
>=20
> gbde attach /dev/concat/datadvd
>=20
> mount -o ro /dev/concat/datadvd.bde  /mnt/dvd
> ----------------------------------------------------------
>=20
> The technique worked fine in  February 2005, with whatever was the latest=
=20
> release, I haven't used the technique since then until a few days ago,  b=
ut=20
> now I'm having a problem with FreeBSD 6.1. After the mdconfig I get "WARN=
ING:=20
> opening backing store: /dvdrw/d1 readonly", which I doubt is the problem.=
 The=20
> failure occurs here:
>=20
> # gbde attach /dev/concat/datadvd
> Enter passphrase:
> gbde: Attach to concat/datadvd failed: could not access consumer
>=20
>=20
> The same problem exists on a newly created disk, so it probably not=20
> corruption. And if I copy the two file to hard disk it works.  It just se=
ems=20
> to be a problem when they are on the DVD.
>=20
> Any ideas on how to fix this. I'm not particularly bothered about the exi=
sting=20
> disks, but I'd like to create some new ones.

The problem is because gbde(4) tries to open provider read-write, which
is not possible with CD-ROMs. You can work-around it by doing:

	(insert 1st CD)
	# dd if=3D/dev/acd0 of=3D/dvdrw/d1 bs=3D1m
	(insert 2nd CD)
	# dd if=3D/dev/acd0 of=3D/dvdrw/d2 bs=3D1m
	# mdconfig -a -f /dvdrw/d1 -u 31
	# mdconfig -a -f /dvdrw/d2 -u 32
	# gconcat create datadvd /dev/md31 /dev/md32
	# gbde attach /dev/concat/datadvd

--=20
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd@FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!

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