[dm-crypt] Open raid1 with luks encryption after a raid re-create

Arno Wagner arno at wagner.name
Tue Nov 24 13:52:03 CET 2015


Excellent! You are welcome.

Regards,
Arno

On Tue, Nov 24, 2015 at 12:15:18 CET, Luis Alexandre wrote:
> 
> Dear Arno and Sven,
> 
> Thanks very much for your support.
> 
> I was able to open the copy I made with
> 
> tail -c +135266305 /dev/sdx > /dev/sdy
> and
> cryptsetup luksOpen /dev/sdy e1
> 
> and have all my data back.
> 
> Thanks again for your support.
> 
> Best regards,
> Luis
> 
> On 23-11-2015 06:26, Arno Wagner wrote:
> >On Mon, Nov 23, 2015 at 04:56:34 CET, Sven Eschenberg wrote:
> >>
> >>
> >>Am 23.11.2015 um 04:35 schrieb Arno Wagner:
> >>>On Sun, Nov 22, 2015 at 23:30:23 CET, Sven Eschenberg wrote:
> >>>[...]
> >>>>Now to your question, once you know the offset of the header:
> >>>>1.)Setup a loop device from your image (You can use an offset into
> >>>>the image where your loop device starts with sector 0) see --offset
> >>>>in losetup man page.
> >>>
> >>>Ah, yes. That would save copying it.
> >>
> >>That was the plan. In general using dmsetup to create a mapping
> >>manually should work too, if loop device support is missing -
> >>dmsetup is pretty cryptic to use though.
> >
> >"Cryptic" is not good here...
> >
> >I was not aware that losetup allows read-only mappings, or I
> >would probably have looked at it too.
> >
> >Excellent! So I learned something too!
> >
> >>>>Inspect loopdevice if the LUKS Header now is on sector 0
> >>>>2.)Try a cryptsetup luksopen in readonly mode
> >>>
> >>>Good idea. With that it may be reasonaly safe to work
> >>>with the original disk. I still would make a full
> >>>backup before.
> >>>
> >>>Regards,
> >>>Arno
> >>>
> >>
> >>Well, I thought about using the loop on the file while the physical
> >>disk stays unchanged. Otherwise it would be possible to work on the
> >>physical disk, and keep a safety image. No matter which way one
> >>chooses, always have a safety copy.
> >>
> >>If the disk is having mechanical problems or something similiar one
> >>would of course use 2 images, one 'master binary backup' and the
> >>replica to work on.
> >>
> >>Once mapping and opening works, one can choose to either copy out
> >>the files and backup (usually a good idea) or to create a copy in
> >>the manner you described. Possibly such an image could then be
> >>remerged onto a new clean array, if it is otherwise intact. Not
> >>without some remaining risks though.
> >
> >Indeed. And first things first, lets see whether that header is
> >viable before goping any further.
> >
> >Regards,
> >Arno
> >
> 
> 
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-- 
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
----
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