[dm-crypt] recovering forgotten passwords for 2 LVs

Arno Wagner arno at wagner.name
Tue Aug 23 14:57:59 CEST 2011

On Mon, Aug 22, 2011 at 06:33:30PM -0400, ken wrote:
> Yves, thanks for replying.
> This setup worked fine for years without changing anything on it.  I'm
> fairly certain that there are two logical volumes on /dev/sda5, both
> encrypted.  As said, when I booted the system up, I was prompted for two
> passphrases (one for each filesystem).
> Does this tell us anything?
> # cryptsetup luksDump /dev/sda5
> LUKS header information for /dev/sda5
> Version:        1
> Cipher name:    aes

It does. /dev/sda5 has a LUKS container at the start with
one passphrase active. For password breaking attempts, it 
does not matter that there are some LVM mappings. I advise 
to just ignore any LVM stuff for the moment and to run your 
password guessing attempts against /dev/sda5. 

You will possibly not get you data, but the password checking 
will be good, unless that thing was created using 
decrypt_derived or the like. I doubt that, as then you 
should have been asked only for one password.

Once you have the password recovered, you should be able
to do a normal boot.

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