[dm-crypt] clarify luksHeaderBackup

Arno Wagner arno at wagner.name
Thu Nov 20 22:06:15 CET 2014

I don't think so. If you have a 512 bit key (or rather a 
double-256 bit one) as used by XTS, your header backup 
is twice as large.

A few more details are in FAQ Ite, 6.12.


On Thu, Nov 20, 2014 at 19:56:42 CET, kqt4at5v at gmail.com wrote:
> I have 2 partitions mirrored, with Luks on top
> md4 : active raid1 sdb4[0] sda4[1]
>       1932713920 blocks [2/2] [UU]
> I run
> cryptsetup  luksHeaderBackup /dev/md4 --header-backup-file nsa320_dm_crypt_header_md4_20141120
> and get
> -r-------- 1 root root 2097152 Nov 20 11:16 nsa320_dm_crypt_header_md4_20141120
> which is twice the size of the header backup of a single drive
> Am I doing this wrong?
> Richard
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Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
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