Provided by: cryptsetup-bin_1.6.6-5ubuntu2_i386 bug


       cryptsetup-reencrypt - tool for offline LUKS device re-encryption


       cryptsetup-reencrypt <options> <device>


       Cryptsetup-reencrypt  can  be  used  to  change reencryption parameters
       which otherwise require full on-disk data change (re-encryption).

       You can regenerate volume key (the real key used in on-disk  encryption
       unclocked by passphrase), cipher, cipher mode.

       Cryptsetup-reencrypt  reencrypts  data  on LUKS device in-place. During
       reencryption process the LUKS device is marked unavailable.

       WARNING: The cryptsetup-reencrypt program is not resistant to  hardware
       or  kernel  failures during reencryption (you can lose you data in this


       The reencryption can be temporarily suspended (by  TERM  signal  or  by
       using   ctrl+c)   but   you   need  to  retain  temporary  files  named
       LUKS-<uuid>.[log|org|new].    LUKS   device   is   unavailable    until
       reencryption is finished though.

       Current  working directory must by writable and temporary files created
       during reencryption must be present.

       For more info about LUKS see cryptsetup(8).


       To start (or continue) re-encryption for <device> use:

       cryptsetup-reencrypt <device>

       <options> can be [--block-size, --cipher, --hash,  --iter-time,  --use-
       random   |  --use-urandom,  --key-file,  --key-slot,  --keyfile-offset,
       --keyfile-size, --tries, --use-directio, --use-fsync, --write-log]

       For detailed  description  of  encryption  and  key  file  options  see
       cryptsetup(8) man page.

       --verbose, -v
              Print more information on command execution.

              Run  in debug mode with full diagnostic logs. Debug output lines
              are always prefixed by '#'.

       --cipher, -c <cipher-spec>
              Set the cipher specification string.

       --key-size, -s <bits>
              Set key size in bits. The argument has to be a multiple of  8.

              The possible key-sizes are limited by the cipher and mode used.

              If you are increasing key size, there must be  enough  space  in
              the LUKS header for enlarged keyslots (data offset must be large
              enough) or reencryption cannot be performed.

              If there is not enough space for keyslots with new key size, you
              can   destructively   shrink  device  with  --reduce-device-size

       --hash, -h <hash-spec>
              Specifies the hash used in the LUKS key setup scheme and  volume
              key digest.

              NOTE: if this parameter is not specified, default hash algorithm
              is always used for new device header.

       --iter-time, -i <milliseconds>
              The number of  milliseconds  to  spend  with  PBKDF2  passphrase
              processing for the new LUKS header.


              Define  which  kernel  random  number  generator will be used to
              create the volume key.

       --key-file, -d name
              Read the passphrase from file.

              WARNING: --key-file option can be used only if  there  only  one
              active  keyslot,  or alternatively, also if --key-slot option is
              specified (then all other keyslots will be disabled in new  LUKS

              If  this  option  is not used, cryptsetup-reencrypt will ask for
              all active keyslot passphrases.

       --key-slot, -S <0-7>
              Specify which key slot is used.

              WARNING: All other keyslots will be disabled if this  option  is

       --keyfile-offset value
              Skip value bytes at the beginning of the key file.

       --keyfile-size, -l
              Read  a maximum of value bytes from the key file.  Default is to
              read the whole file up to the compiled-in maximum.

              Do not change encryption key, just reencrypt the LUKS header and

              This  option  can  be  combined  only with --hash or --iter-time

       --tries, -T
              Number of retries for invalid passphrase entry.

       --block-size, -B value
              Use re-encryption block size of <value> in MiB.

              Values can be between 1 and 64 MiB.

       --device-size size[units]
              Instead of real device size, use specified value.

              It means that only specified area (from the start of the  device
              to the specified size) will be reencrypted.

              WARNING: This is destructive operation.

              If no unit suffix is specified, the size is in bytes.

              Unit  suffix  can  be  S  for  512  byte  sectors,  K/M/G/T  (or
              KiB,MiB,GiB,TiB) for units with 1024  base  or  KB/MB/GB/TB  for
              1000 base (SI scale).

              WARNING: This is destructive operation.

       --reduce-device-size size[units]
              Enlarge data offset to specified value by shrinking device size.

              This  means  that  last  sectors  on the original device will be
              lost, ciphertext data will be effectively shifted  by  specified
              number of sectors.

              It  can  be  useful  if  you e.g. added some space to underlying
              partition (so last sectors contains no data).

              For units suffix see --device-size parameter description.

              WARNING: This is destructive operation and cannot  be  reverted.
              Use  with  extreme  care  -  shrinked  filesystems  are  usually

              You cannot shrink device more than by 64 MiB (131072 sectors).

       --new, N
              Create new header (encrypt not yet encrypted device).

              This option must be used together with --reduce-device-size.

              WARNING: This is destructive operation and cannot be reverted.

              Use direct-io (O_DIRECT) for all read/write data operations.

              Useful  if  direct-io  operations  perform  better  than  normal
              buffered operations (e.g. in virtual environments).

              Use fsync call after every written block.

              Update  log  file  after  every  block write. This can slow down
              reencryption but will minimize data loss in the case  of  system

       --batch-mode, -q
              Suppresses all warnings and reencryption progress output.

              Show the program version.


       Cryptsetup-reencrypt  returns  0  on  success  and  a non-zero value on

       Error codes are: 1 wrong parameters, 2 no permission, 3 out of  memory,
       4 wrong device specified, 5 device already exists or device is busy.


       Reencrypt /dev/sdb1 (change volume key)
              cryptsetup-reencrypt /dev/sdb1

       Reencrypt and also change cipher and cipher mode
              cryptsetup-reencrypt /dev/sdb1 -c aes-xts-plain64

       Add LUKS encryption to not yet encrypted device

              First, be sure you have space added to disk.

              Or alternatively shrink filesystem in advance.
              Here we need 4096 512-bytes sectors (enough for 2x128 bit key).

              fdisk  -u  /dev/sdb # move sdb1 partition end + 4096 sectors (or
              use resize2fs or tool for your filesystem and shrink it)

              cryptsetup-reencrypt /dev/sdb1 --new --reduce-device-size 4096S


       Report bugs, including ones in the  documentation,  on  the  cryptsetup
       mailing  list at <> or in the 'Issues' section on LUKS
       website.  Please attach the output  of  the  failed  command  with  the
       --debug option added.


       Cryptsetup-reencrypt was written by Milan Broz <>.


       Copyright © 2012-2014 Milan Broz
       Copyright © 2012-2013 Red Hat, Inc.

       This is free software; see the source for copying conditions.  There is
       NO warranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR


       The project website at