Provided by: cryptsetup-bin_2.2.0-3ubuntu1_amd64 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 your data in this case).

       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 be 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 [--batch-mode, --block-size, --cipher |  --keep-key,  --debug,  --device-
       size,  --hash,  --header,  --iter-time | --pbkdf-force-iterations, --key-file, --key-size,
       --key-slot,  --keyfile-offset,  --keyfile-size,   --master-key-file,   --tries,   --pbkdf,
       --pbkdf-memory,  --pbkdf-parallel,  --progress-frequency,  --use-directio,  --use-random |
       --use-urandom, --use-fsync, --uuid, --verbose, --write-log]

       To encrypt data on (not yet encrypted) device, use --new  in  combination  with  --reduce-
       device-size or with --header option for detached header.

       To remove encryption from device, use --decrypt.

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

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

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

              Values can be between 1 and 64 MiB.

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

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

              Remove encryption (decrypt already encrypted device and remove LUKS header).

              WARNING: This is destructive operation and cannot be reverted.

       --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.

              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.

       --hash, -h <hash-spec>
              Specifies the hash used in the LUKS1 key setup scheme and volume key digest.

              NOTE: if this parameter is not specified, default hash algorithm is always used for
              new LUKS1 device header.

              NOTE:  with  LUKS2  format  this  option  is  only  relevant when new keyslot pbkdf
              algorithm is set to PBKDF2 (see --pbkdf).

       --header <LUKS header file>
              Use a detached (separated) metadata device or file where the LUKS header is stored.
              This option allows one to store ciphertext and LUKS header on different devices.

              WARNING: There is no check whether the ciphertext device specified actually belongs
              to the header given.  If used with --new option, the header file will  created  (or
              overwritten).  Use with care.

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

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

              This    option    can    be    combined    only    with    --hash,     --iter-time,
              --pbkdf-force-iterations,  --pbkdf  (LUKS2  only),  --pbkdf-memory  (Argon2i/id and
              LUKS2 only) and --pbkdf-parallel (Argon2i/id and LUKS2 only) options.

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

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

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

       --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

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

       --key-slot, -S <0-MAX>
              Specify which key slot is used. For LUKS1, max keyslot number is 7. For LUKS2, it's

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

       --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.

              Use new volume (master) key stored in a file.

       --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.

              Set Password-Based Key Derivation Function (PBKDF) algorithm for LUKS keyslot.  The
              PBKDF can be: pbkdf2, argon2i for Argon2i or argon2id for Argon2id.

              For LUKS1, only pbkdf2 is accepted (no need to use this option).

       --pbkdf-force-iterations <num>
              Avoid PBKDF benchmark and set time cost (iterations) directly.

       --pbkdf-memory <number>
              Set  the  memory  cost  for PBKDF (for Argon2i/id the number represents kilobytes).
              Note that it is maximal value, PBKDF benchmark or  available  physical  memory  can
              decrease it.  This option is not available for PBKDF2.

       --pbkdf-parallel <number>
              Set  the  parallel  cost  for  PBKDF (number of threads, up to 4).  Note that it is
              maximal value, it is decreased automatically if CPU online count  is  lower.   This
              option is not available for PBKDF2.

       --progress-frequency <seconds>
              Print separate line every <seconds> with reencryption progress.

       --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.

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

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

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

       --type <type>
              Use only while encrypting not yet encrypted device (see --new).

              Specify LUKS version when performing  in-place  encryption.  If  the  parameter  is
              omitted default value (LUKS1) is used. Type may be one of: luks (default), luks1 or

              Use direct-io (O_DIRECT) for all read/write data operations related to block device
              undergoing reencryption.

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

              Use fsync call after every written block. This applies for reencryption  log  files
              as well.


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

       --uuid <uuid>
              Use only while resuming an interrupted decryption process (see --decrypt).

              To find out what <uuid> to pass look for temporary files LUKS-<uuid>.[|log|org|new]
              of the interrupted decryption process.

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

              Show the program version.

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


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

       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

       Remove LUKS encryption completely

              cryptsetup-reencrypt /dev/sdb1 --decrypt


       Report  bugs,  including ones in the documentation, on the cryptsetup mailing list at <dm-> 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 © 2012-2019 Milan Broz
       Copyright © 2012-2019 Red Hat, Inc.

       This  is  free software; see the source for copying conditions.  There is NO warranty; not


       The project website at