[dm-crypt] "not a valid LUKS device" after distro change

Arno Wagner arno at wagner.name
Fri Aug 22 13:55:16 CEST 2014


On Fri, Aug 22, 2014 at 11:08:56 CEST, Jonas Meurer wrote:
> Hi John, 
> Am 21.08.2014 um 22:46 schrieb John Wells:
[...]
> As Arno already wrote, the hexdump from your meant-to-be LUKS container
> on HOME_LV in FINALFRONTIER_VG doesn't look too promising. I've never
> heard about 'GNU Parted Loopback 0' before, but it sounds like something
> caused Parted to overwrite your LUKS header.

Not necessarily. The other container had that in it the one time as 
well, but it fixed itself ...
 
> Last hope is to find the LUKS header with an offset on the partition.
> Try to search for 'LUKS' by grepping the output of 'strings
> /dev/FINALFRONTIER_VG/HOME_LV'. If you don't find the string 'LUKS'
> followed by something describing your cipher and hash algorithm, I fear
> that this second partition is lost.

I second searching for that. It may not be the only way though.
Easy way to search:

hd <partition> | grep "LUKS"

That gives you hex offset(s) to examine further. 

> According to your hexdump it's not astonishing at all that neither of
> the distros do recognize the FINALFRONTIER_VG/HOME_LV logical volume as
> LUKS container. It simply doesn't start with a LUKS header.
> 
> The question rather is: what action resulted in the LUKS header being
> overwritten. In the past the partition configuration in the Ubuntu
> installer was kind of confusing, and some people trashed their existent
> LUKS containers by reformatting them as new LUKS container, but it
> doesn't look like that happened to you.

I think it is configuration mis-detection and with a randomized
component.
 
> I don't want to join the rant against modern Linux distros, LVM and MD-1
> format here. In fact there've been quite some serious bugs in Linux
> (vanilla kernel, userspace tools as well as distro implementations) in
> the past, and ranting about how fucked up everything is today compared
> to the good all days doesn't help to fix them. I prefer to isolate,
> identify and fix the bugs and improve the user experience that way :)

I am not ranting about bugs, I am ranting about broken architecture
and KISS violations. Having seens some commercial software 
source code, I do know that there, it often is even worse. There
are just to many peiople creating software that are not good at
it, and FOSS is really no exception.

Arno
-- 
Arno Wagner,     Dr. sc. techn., Dipl. Inform.,    Email: arno at wagner.name
GnuPG: ID: CB5D9718  FP: 12D6 C03B 1B30 33BB 13CF  B774 E35C 5FA1 CB5D 9718
----
A good decision is based on knowledge and not on numbers. -  Plato


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