[dm-crypt] Restore a LUKS partition

Arno Wagner arno at wagner.name
Thu Nov 21 02:57:45 CET 2013

On Thu, Nov 21, 2013 at 02:25:16 CET, Michael Grosseck wrote:
> Hello,
> I created a luks partition for a long time with Ubuntu 10.04. Most
> likely I used following command to create it.
> # cryptsetup -c blowfish-cbc-essiv:sha256 -y -s 256 luksFormat /dev/sda6
> In the meantime I changed the distro to Linux Mint 13.
> Now I tried to open it, but I get an error. Also if I try to dump
> the header information.
> $ sudo cryptsetup luksDump -vc blowfish-cbc-essiv:sha256 /dev/sda6
> Device /dev/sda6 is not a valid LUKS device.
> Command failed with code 22: Device /dev/sda6 is not a valid LUKS device.

Use cryptsetup -v isLuks to find whether it is a LUKS container,
no other parameters.

> I was not sure if the drive is a LUKS device at all and I have read
> in another forum I should search for LUKS, what I did.
> $ sudo dd if=/dev/sda6 | grep -a -b LUKS
> 0:�������?1�U�LUKS��blowfishcbc-essiv:sha256sh
> E������֬�y[8�@��/�ā�]1b(�?K 
> 362478668:rC�+9���\D�#�8*tfoye�/�34ڛ�OCI[���5���E!U�3_B��%�rLUKS�$i}�H�[g>�rw̋��G�O
> �����6��>�b��s��e$�tɞV

That is not the way to search. Better post what
  hd /dev/sda6 | head 
gives you. 
> So indeed it seems a LUKS device, but the header is somehow corrupt.
> Now I tried to make a plain mapping what unexpected really works.
> But the joy was short. I can not mount the mapped device.

You can always create a plain mapping, there is no error checking
as a plain device has no header.

> $ sudo cryptsetup create -c blowfish-cbc-essiv:sha256 -s 256 crypt /dev/sda6
> Enter passphrase:
> $ sudo mount /dev/mapper/crypt /home/crypt/
> mount: you must specify the filesystem type
> $ sudo mount -t ext3 /dev/mapper/crypt /home/crypt/
> mount: wrong fs type, bad option, bad superblock on /dev/mapper/crypt,
> missing codepage or helper program, or other error
> In some cases useful info is found in syslog - try
> dmesg | tail or so
> Now my question. Is there a little hope to restore the LUKS header
> or at least to read the content of this partition somehow?

Completely unclear at this time. 

> Thanks for your help
> Michael
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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
There are two ways of constructing a software design: One way is to make it
so simple that there are obviously no deficiencies, and the other way is to
make it so complicated that there are no obvious deficiencies. The first
method is far more difficult.  --Tony Hoare

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