From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <dpchrist@holgerdanske.com>
Received: from holgerdanske.com (holgerdanske.com
 [IPv6:2001:470:0:19b::b869:801b])
 by mail.server123.net (Postfix) with SMTP
 for <dm-crypt@saout.de>; Wed,  6 Apr 2016 21:35:23 +0200 (CEST)
Received: from ::ffff:99.100.19.101 ([99.100.19.101]) by holgerdanske.com
 for <dm-crypt@saout.de>; Wed, 6 Apr 2016 12:35:17 -0700
References: <57048FA2.7090008@holgerdanske.com>
 <20160406105535.GG9664@yeono.kjorling.se>
From: David Christensen <dpchrist@holgerdanske.com>
Message-ID: <57056507.6020907@holgerdanske.com>
Date: Wed, 6 Apr 2016 12:35:35 -0700
MIME-Version: 1.0
In-Reply-To: <20160406105535.GG9664@yeono.kjorling.se>
Content-Type: text/plain; charset="utf-8"; format="flowed"
Content-Transfer-Encoding: 8bit
Subject: Re: [dm-crypt] Debian 7.10 random key swap Device /dev/sda2 is not
 a valid LUKS device.
List-Id: <dm-crypt.saout.de>
List-Unsubscribe: <http://www.saout.de/mailman/options/dm-crypt>,
 <mailto:dm-crypt-request@saout.de?subject=unsubscribe>
List-Archive: <http://www.saout.de/pipermail/dm-crypt/>
List-Post: <mailto:dm-crypt@saout.de>
List-Help: <mailto:dm-crypt-request@saout.de?subject=help>
List-Subscribe: <http://www.saout.de/mailman/listinfo/dm-crypt>,
 <mailto:dm-crypt-request@saout.de?subject=subscribe>
To: dm-crypt@saout.de

On 04/06/2016 03:55 AM, Michael Kjörling wrote:
> On 5 Apr 2016 21:25 -0700, from dpchrist@holgerdanske.com (David Christensen):
>> # grep sda2 /etc/crypttab
>> sda2_crypt /dev/sda2                                 /dev/urandom
>> cipher=aes-xts-plain64,size=256,swap
>
> Since you don't have the "luks" option, Debian does not treat this as
> a LUKS device. So when cryptsetup claims that /dev/sda2 "is not a
> valid LUKS device" it is quite correct.
>

Thanks for the information.


So, RTFM 'crypttab':  at boot time /sbin/cryptdisks_start will create a 
plain dm-crypt device with target name 'sda2_crypt' 
(/dev/mapper/sda2_crypt) from source device /dev/sda2 with a 256-bit key 
(option 'size') from file /dev/urandom and with cipher aes-xts-plain64 
(option 'cipher'), and then run /sbin/mkswap on the created device 
(option 'swap') (?).


And, as plain dm-crypt devices do not have a LUKS header, 
'luksHeaderBackup' has nothing to back up and the error message I'm 
seeing is expected and correct (?).


David