[dm-crypt] password recovery for a luksOpened device?

Arno Wagner arno at wagner.name
Wed Nov 2 08:25:29 CET 2011

You have to go trough master key recovery. No way around that.

But you do not need to create a new header, you can use
something like "cryptsetup luksAddKey --master-key-file <mkey> ..."
to set a new passphrase. (In this case you have to go the
manual route.) I am currently adding this to the FAQ, 
may take a few minutes to try it out.

On Wed, Nov 02, 2011 at 04:14:30AM +0100, mike dentifrice wrote:
> Hey there,
> I managed to forget the passphrase for a server (it is very rarely
> rebooted). 
> It it still running, the LUKS device is opened, and the filesystem
> laying on top of it is mounted. 
> So, I do have a fresh backup, and can keep on trying to remember the
> passphrase with `cryptsetup luksAddKey /dev/mapper/foobar`
> However, it would be a lot of hasle to re-install the system entirely,
> as the services cannot suffer a long downtime.
> Is there a way to recover the passphrase or add a new keyslot while the
> system's running, the crypto device mounted, the fs opened? 
> Or do I necessarily have to jump towards the "How do I recover the
> master key from a mapped LUKS container?" FAQ entry?
> Thanks in advance for your answer,
> -- 
> mike dentifrice <fluor at poivron.org>
> _______________________________________________
> dm-crypt mailing list
> dm-crypt at saout.de
> http://www.saout.de/mailman/listinfo/dm-crypt

Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno at wagner.name 
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