[dm-crypt] Cryptsetup-reencrypt failing with error with option --new reduce-device-size

Abhrajyoti Kirtania abhrajyoti at gmail.com
Fri Jun 20 16:16:33 CEST 2014

Thank you for the reply.

How can i create unused space (shrink) at the end of original divide? As
per the man page "fdisk -u /dev/sdb # move sdb1 partition end + 4096
sectors" not giving expected result.

Even i tried with resize2fs but not helping

test at ubuntu:~/in-place$ sudo resize2fs /dev/sda8 4M

resize2fs 1.42.5 (29-Jul-2012)

resize2fs: New size smaller than minimum (45572)

test at ubuntu:~/in-place$ sudo resize2fs /dev/sda8 8M

resize2fs 1.42.5 (29-Jul-2012)

resize2fs: New size smaller than minimum (45572)

On Fri, Jun 20, 2014 at 6:59 PM, Ondrej Kozina <okozina at redhat.com> wrote:

> On 06/20/2014 02:36 PM, Abhrajyoti Kirtania wrote:
>> HI,
>> I able to build the crypt setup-reencrypt binary and trying to enable
>> encryption on a particular partition with this tool, build failing with
>> error like:
>> *Cannot wipe header on device /dev/loop0. if i pass
>> *--reduce-device-size as 1024. But if i pass this size as 4096 then
>> getting the error as "Device /dev/loop0 is too small."
>> Not sure what might be the root cause of this error. Truly appreciate
>> your kind support?
>> cryptsetup-reencrypt /dev/sda8 --new --reduce-device-size 1024 --debug
>> WARNING: this is experimental code, it can completely break your data.
>> # cryptsetup 1.6.4 processing "./abhra_new/sbin/cryptsetup-reencrypt
>> /dev/sda8 --new --reduce-device-size 1024 --debug"
> Hi Abhrajyoti,
> you have to create enough space to fit new LUKS header during reencryption
> of not yet encrypted device. The LUKS header is approximately 1MiB in size
> (it differs and depends also on other parameters). The default unit for
> --reduce-device-size is a byte. Try to use --reduce-device-size 2048S
> (where 'S' stands for sectors). If I recall correctly --reduce-device-size
> must be aligned to 512B (dm-crypt sector size) or maybe even to page size
> (4 KiB).
> Be extremely careful with the --new option! You have to create unused
> space at the end of the original device which is equal in size to
> --reduce-device-size option. By term unused  I mean there are no real
> filesystem data or any data important to you. Otherwise you will you loose
> this data. The best to achieve this would be to actually extend the partion
> or LV at its end exactly by intended --redude-device-size parameter first.
> Kind regards
> Ondrej
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