[dm-crypt] Detached header offset

Arno Wagner arno at wagner.name
Thu Apr 13 15:36:18 CEST 2017

Hi Theo,

since it is a detached header, you could probably do a mapping 
to file from the raw sectors, using losetup like this

  losetup -o offset --sizelimit <header size>  /dev/loop0 <dev_raw_disk>

and then use that as the file-argument for the detached header.

I would say that this is exceedingly "hackish" and probably 
asking for a lot of potentially painful problems.

You could probably also (even worse idea) use LVM to combine 
the sectors for the header and the ones for the data into a 
complete LUKS device (i.e. no detached header in the final thing).


On Thu, Apr 13, 2017 at 12:18:08 CEST, 7heo wrote:
> Hey all,
> I assumed that there was on option to give the offset of the header on a
> disk, but this option is only accepted for loopaes and plain devices,
> according to the man.
> There's another option to give an offset, for the key-file, but as far as I
> could understand, this is for the offset of the key slots relatively to the
> start of the partition they're on.
> Also --align-payload only works on the data.
> So is there a way to place a detached header arbitrarily on a disk, and not
> at the start of a partition?
> Best regards,
> Theo.
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Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
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