From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <mbroz@redhat.com>
Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28])
	by mail.saout.de (Postfix) with ESMTP
	for <dm-crypt@saout.de>; Thu, 26 Aug 2010 00:58:06 +0200 (CEST)
Message-ID: <4C759FF8.5060100@redhat.com>
Date: Thu, 26 Aug 2010 00:58:00 +0200
From: Milan Broz <mbroz@redhat.com>
MIME-Version: 1.0
References: <AANLkTing13-W-R0rKXQrEZ4a5cKrbjx=HtzFfGpNtsmu@mail.gmail.com>
In-Reply-To: <AANLkTing13-W-R0rKXQrEZ4a5cKrbjx=HtzFfGpNtsmu@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Re: [dm-crypt] cryptsetup align problem
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: Peter Smith <peter.smith3882100@gmail.com>
Cc: dm-crypt@saout.de


On 08/25/2010 11:50 PM, Peter Smith wrote:
> I am trying to align a LUKS volume to 512K boundary. I calculate the
> --align-payload value like this:
> 
> (512*1024) / 512 = 1024
> 
> cryptsetup luksFormat --align-payload=1024 /dev/sda1
> 
> When i confirm the task with cryptsetup luksDump /dev/sda2 the Payload
> offset is set to 2048 which is 1024K?
> 
> What am i doing wrong?

Nothing, it works as expected. It is not fixed offset but req. alignment.

Using --align-payload=1024 means alignment to the nearest 512KiB boundary,
because the keyslots space requires more than 512KiB it aligns to next multiple
of it - i.e. 2048 sectors.

If you increase key size (thus keyslots size), it will probably switch to to 3072 etc.

Milan