[dm-crypt] change passphrase

Heiko Rosemann heiko.rosemann at web.de
Tue Apr 1 23:21:31 CEST 2014


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On 04/01/2014 09:02 PM, Biltong wrote:
> I have a raid-1 system running btrfs on top of luks.
> 
> I cannot remember my passphrase, but the system is running and I
> have made a backup.
> 
> I'd like to add a new passphrase, and have followed the
> instructions from 6.10 at
> 
http://code.google.com/p/cryptsetup/wiki/FrequentlyAskedQuestions#6._Backup_and_Data_Recovery
> 
> This worked for the first device, which seems to work with
> /dev/dm-0, but I cannot work out what the device name for the
> second raid-1 member is. The btrfs partition is on top of the luks
> device, and so I need to change both.
> 

I'm not really clear on what your setup is, but there's basically two
choices:

1) encrypt 2 partitions separately (typically /dev/sdxy with x in a..z
and y in
1..) leading to /dev/mapper/a and /dev/mapper/b as links to /dev/dm-0
and /dev/dm-1
2) create RAID1 from /dev/mapper/a and /dev/mapper/b, causing /dev/md0
to appear
3) create btrfs (or whatever) on top of /dev/md0

or

1) create RAID1 from 2 partitions (typically /dev/sdxy as above) leading
to /dev/md0
2) encrypt /dev/md0 leading to /dev/mapper/a as a link to /dev/dm-0
3) create btrfs (or whatever) on top of /dev/dm-0


If you can't find /dev/dm-1, you might be using the second version. You
can also find some information in the output of the mount command (which
should show you the crypto device in the first and the RAID device in
the second scenario) and from /proc/mdstat showing /dev/mapper/a (or
/dev/dm-0) in the first and /dev/sdxy in the second case.

Good luck with the research,
Heiko

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