CRYPTSETUP-REENCRYPT(8)  (January 2021)   CRYPTSETUP-REENCRYPT(8)

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

     SYNOPSIS
          cryptsetup-reencrypt <options> <device>

     DESCRIPTION
          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.

          NOTE: If you're looking for LUKS2 online reencryption manual
          please read cryptsetup(8) man page instead (see reencrypt
          action). This page is for legacy offline reencryption util-
          ity only.

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

          ALWAYS BE SURE YOU HAVE RELIABLE BACKUP BEFORE USING THIS
          TOOL.
          The reencryption can be temporarily suspended (by TERM sig-
          nal 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).

     OPTIONS
          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,

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          --pbkdf-parallel, --progress-frequency, --use-directio,
          --use-random | --use-urandom, --use-fsync, --uuid, --ver-
          bose, --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 out-
               put.

          --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.

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

          --decrypt
               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

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               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.

          --keep-key
               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 passphrases.

          --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

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               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 option.

          --key-slot, -S <0-MAX>
               Specify which key slot is used. For LUKS1, max keyslot
               number is 7. For LUKS2, it's 31.

               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.

          --master-key-file
               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.

          --pbkdf
               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 num-
               ber represents kilobytes).  Note that it is maximal
               value, PBKDF benchmark or available physical memory can
               decrease it.  This option is not available for PBKDF2.

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          --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 under-
               lying partition (so last sectors contains no data).

               For units suffix see --device-size parameter descrip-
               tion.

               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 encryp-
               tion. If the parameter is omitted default value (LUKS1)
               is used. Type may be one of: luks (default), luks1 or
               luks2.

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

               Useful if direct-io operations perform better than nor-
               mal buffered operations (e.g. in virtual environments).

          --use-fsync
               Use fsync call after every written block. This applies

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               for reencryption log files as well.

          --use-random

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

          --uuid <uuid>
               Use only while resuming an interrupted decryption pro-
               cess (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.

          --version
               Show the program version.

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

     RETURN CODES
          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.

     EXAMPLES
          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

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               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

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

     AUTHORS
          Cryptsetup-reencrypt was written by Milan Broz
          <gmazyland@gmail.com>.

     COPYRIGHT
          Copyright c 2012-2021 Milan Broz
          Copyright c 2012-2021 Red Hat, Inc.

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

     SEE ALSO
          The project website at
          https://gitlab.com/cryptsetup/cryptsetup

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