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  reencryp-
       tion 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  crypt-
       setup(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.

              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  pro-
              cessing for the new LUKS header.


              Define which kernel random number generator will be used to cre-
              ate 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.

              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 par-
              tition (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 unre-

              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,

              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 (C) 2012-2014 Milan Broz
       Copyright (C) 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

cryptsetup-reencrypt             December 2013         CRYPTSETUP-REENCRYPT(8)
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