[dm-crypt] cryptsetup-reencrypt: Specifying device size

Sven Eschenberg sven at whgl.uni-frankfurt.de
Fri Jul 24 11:06:17 CEST 2015


Milan gave quite an extensive answer to your questions.

One thing I want to add, the LVM metadata is stored 2k from the start of
the device - if you only use 1 metadata-copy that is (which is default).

As Milan said, make sure which extents are actually ocupied. As others
mentioned: Backup and then dry run with a mapping of enforced reduced size
to see if the possible result is useable at all.

Regards

-Sven

On Wed, July 22, 2015 15:46, Karol Babioch wrote:
> Hi list,
>
> I'm not familiar enough with the LUKS internals, but I'm pretty sure
> that it is not filesystem aware, so it will only reencrypt the first
> 16GB of the device, while LVM and any filesystems may actually put data
> anywhere on the device.
>
> So am I right in assuming that providing a device size smaller than the
> actual block device size might lead to data corruption or is it safe to
> use it in the way described above?
>
> Best regards,
> Karol Babioch
>
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