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From: Rudolf Deilmann <rudolf.deilmann@gmail.com>
Date: Tue, 22 Mar 2011 19:47:25 +0100
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References: <4D7E53E5.3040007@redhat.com> <20110314221329.19d588ea@gmail.com>
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Subject: Re: [dm-crypt] [ANNOUNCE] cryptsetup 1.3.0-rc1 (test
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On Mon, 21 Mar 2011 19:21:50 +0100
Milan Broz <mbroz@redhat.com> wrote:
> I added offset support, seems loopAES always uses offset==skip
> (IOW initial vector is always related to absolute sector size on the
> device).

No, loopAES supports both options. It depends on user input:

--
-o offset
   The data start is moved offset bytes into the specified file or
   device. Normally offset is included in IV   (initialization
   vector) computations. If offset is prefixed with @ character, then
   offset is not included in IV computations. @ prefix functionality
   may not be supported on some older kernels and/or loop drivers.
--

Both options seems to be supported by dmcrypt/dmsetup. In the first case
IV offset is always identic to the sector offset, in the second case IV
offset is always zero.

(IV offset: 6th value at dmsetup table, sector offset: 8th value. I
hope, I haven't muddle something )

 
> I do not plan to add sizelimit option, this can just cause confusion.
> 
> (In fact you can do that using cryptsetup resize command afterwards
> or by limiting underlying device. If it is problem, please show me
> real example where it is needed.)

Sounds reasonable. It's main usage seems to be recovery if your
partition table is damaged or similar exceptional things happend.