[dm-crypt] Avoiding fsck.ext4 destruction of crypto_luks data

Arno Wagner arno at wagner.name
Sun Dec 30 14:19:39 CET 2012

On Sun, Dec 30, 2012 at 01:25:46PM +0100, Milan Broz wrote:
> On 12/30/2012 01:08 PM, Sven Eschenberg wrote:
> >> I also found that "wipefs"
> >> does not remove matadata 0.90 signatures from md components (located
> >> at the end. I still use them because I like kernel-level autodetection
> >> and my arrays are small), also added warning about that.
> Usual util-linux maintainer response is "send a patch" :-)
> wipefs must work (e.g. anaconda installer depends on the proper sig. erase)
> so it is a bug somewhere.
> Do you have reproducer? (only 0.9 metadata end-of-disk format?)

Reproduce with (adjust loop2 and md12 numbers as needed):
head -c 1M /dev/zero > t
losetup /dev/loop2 t
mdadm --create --metadata=0.90 --force -l 1 -n 1 /dev/md12 /dev/loop2
mdadm --stop /dev/md12
mdadm --examine /dev/loop2
  --> Raid componend with intact magic
wipefs /dev/loop2
mdadm --examine /dev/loop2
  --> same as above, RAID signature still there

Version (Debian stable): util-linux: 2.17.2-9

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
One of the painful things about our time is that those who feel certainty
are stupid, and those with any imagination and understanding are filled
with doubt and indecision. -- Bertrand Russell

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