[dm-crypt] Detached header offset

Milan Broz gmazyland at gmail.com
Thu Apr 13 13:02:45 CEST 2017

On 04/13/2017 12:18 PM, 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.

Neither loopaes nor plain device use header. Where do you see this?

> 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.

All offsets works only for data.

> So is there a way to place a detached header arbitrarily on a disk, and 
> not at the start of a partition?

No. LUKS1 offset always starts at sector 0.
All tools like blkid search for header at this location, you cannot
arbitrarily change offset.

You can only set data payload offset to 0 if detached header is used
(it means that no header is on the data device itself.)


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