cryptsetup-reencrypt(8) — Linux manual page



NAME         top

       cryptsetup-reencrypt - reencrypt LUKS encrypted volumes in-place

SYNOPSIS         top

       cryptsetup reencrypt [<options>] <device> or --active-name <name>

DESCRIPTION         top

       Run LUKS device reencryption.

       There are 3 basic modes of operation:

       •   device reencryption (reencrypt)

       •   device encryption (reencrypt --encrypt/--new/-N)

       •   device decryption (reencrypt --decrypt)

       <device> or --active-name <name> (LUKS2 only) is mandatory

       Cryptsetup reencrypt action can be used to change reencryption
       parameters which otherwise require full on-disk data change
       (re-encryption). The reencrypt action reencrypts data on LUKS
       device in-place.

       You can regenerate volume key (the real key used in on-disk
       encryption unclocked by passphrase), cipher, cipher mode or
       encryption sector size (LUKS2 only).

       Reencryption process may be safely interrupted by a user via
       SIGINT signal (ctrl+c). Same applies to SIGTERM signal (i.e.
       issued by systemd during system shutdown).

       For in-place encryption mode, the reencrypt action additionally
       takes all options available for luksFormat action for respective
       LUKS version (see cryptsetup-luksFormat man page for more
       details). See cryptsetup-luksFormat(8).

       NOTE that for encrypt and decrypt mode, the whole device must be
       treated as unencrypted — there are no quarantees of
       confidentiality as part of the device contains plaintext.


       <options> can be [--batch-mode, --block-size, --cipher, --debug,
       --debug-json, --decrypt, --device-size, --disable-locks,
       --encrypt, --force-offline-reencrypt, --hash, --header,
       --hotzone-size, --iter-time, --init-only, --keep-key, --key-file,
       --key-size, --key-slot, --keyfile-offset, --keyfile-size,
       --tries, --timeout, --pbkdf, --pbkdf-force-iterations,
       --pbkdf-memory, --pbkdf-parallel, --progress-frequency,
       --progress-json, --reduce-device-size, --resilience,
       --resilience-hash, --resume-only, --sector-size, --use-directio,
       --use-random, --use-urandom, --use-fsync, --uuid, --verbose,
       --volume-key-file, --write-log].


       With <device> parameter cryptsetup looks up active <device> dm
       mapping. If no active mapping is detected, it starts offline
       LUKS2 reencryption otherwise online reencryption takes place.

       To resume already initialized or interrupted reencryption, just
       run the cryptsetup reencrypt command again to continue the
       reencryption operation. Reencryption may be resumed with
       different --resilience or --hotzone-size unless implicit
       datashift resilience mode is used: either encrypt mode with
       --reduce-device-size option or decrypt mode with original LUKS2
       header exported in --header file.

       If the reencryption process was interrupted abruptly
       (reencryption process crash, system crash, poweroff) it may
       require recovery. The recovery is currently run automatically on
       next activation (action open) when needed or explicitly by user
       (action repair).

       Optional parameter <new_name> takes effect only with encrypt
       option and it activates device <new_name> immediately after
       encryption initialization gets finished. That’s useful when
       device needs to be ready as soon as possible and mounted (used)
       before full data area encryption is completed.


       Current working directory must be writable and temporary files
       created during reencryption must be present. During reencryption
       process the LUKS1 device is marked unavailable and must be
       offline (no dm-crypt mapping or mounted filesystem).

       WARNING: The LUKS1 reencryption code is not resistant to hardware
       or kernel failures during reencryption (you can lose your data in
       this case).

OPTIONS         top

       --block-size value (LUKS1 only)
           Use re-encryption block size of value in MiB.

           Values can be between 1 and 64 MiB.

       --use-directio (LUKS1 only)
           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 (LUKS1 only)
           Use fsync call after every written block. This applies for
           reencryption log files as well.

       --write-log (LUKS1 only)
           Update log file after every block write. This can slow down
           reencryption but will minimize data loss in the case of
           system crash.

       --type <device-type>
           Specifies required (encryption mode) or expected (other
           modes) LUKS format. Accepts only luks1 or luks2.

       --hash, -h <hash-spec>
           LUKS1: 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.

           LUKS2: Ignored unless new keyslot pbkdf algorithm is set to
           PBKDF2 (see --pbkdf).

       --cipher, -c <cipher-spec>
           LUKS2: Set the cipher specification string for data segment

           LUKS1: Set the cipher specification string for data segment
           and keyslots.

           NOTE: In encrypt mode, if cipher specification is omitted the
           default cipher is applied. In reencrypt mode, if no new
           cipher specification is requested, the existing cipher will
           remain in use. Unless the existing cipher was "cipher_null".
           In that case default cipher would be applied as in encrypt

           cryptsetup --help shows the compiled-in defaults.

           If a hash is part of the cipher specification, then it is
           used as part of the IV generation. For example, ESSIV needs a
           hash function, while "plain64" does not and hence none is

           For XTS mode you can optionally set a key size of 512 bits
           with the -s option. Key size for XTS mode is twice that for
           other modes for the same security level.

       --verify-passphrase, -y
           When interactively asking for a passphrase, ask for it twice
           and complain if both inputs do not match. Ignored on input
           from file or stdin.

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

           If the name given is "-", then the passphrase will be read
           from stdin. In this case, reading will not stop at newline

           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 will ask for all
           active keyslot passphrases.

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

       --keyfile-size, -l value
           Read a maximum of value bytes from the key file. The default
           is to read the whole file up to the compiled-in maximum that
           can be queried with --help. Supplying more data than the
           compiled-in maximum aborts the operation.

           This option is useful to cut trailing newlines, for example.
           If --keyfile-offset is also given, the size count starts
           after the offset.

       --volume-key-file, --master-key-file (OBSOLETE alias)
           Use (set) new volume key stored in a file.
           WARNING: If you create your own volume key, you need to make
           sure to do it right. Otherwise, you can end up with a
           low-entropy or otherwise partially predictable volume key
           which will compromise security.

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

           LUKS2: Do not change effective volume key and change other
           parameters provided it is requested.

           LUKS1: Reencrypt only the LUKS1 header and keyslots. Skips
           data in-place reencryption.

       --key-slot, -S <0-N>
           For LUKS operations that add key material, this option allows
           you to specify which key slot is selected for the new key.

           For reencryption mode it selects specific keyslot (and
           passphrase) that can be used to unlock new volume key. If
           used all other keyslots get removed after reencryption
           operation is finished.

           The maximum number of key slots depends on the LUKS version.
           LUKS1 can have up to 8 key slots. LUKS2 can have up to 32 key
           slots based on key slot area size and key size, but a valid
           key slot ID can always be between 0 and 31 for LUKS2.

       --key-size, -s bits
           Sets key size in bits. The argument has to be a multiple of
           8. The possible key-sizes are limited by the cipher and mode

           See /proc/crypto for more information. Note that key-size in
           /proc/crypto is stated in bytes.

           LUKS1: 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

       --offset, -o <number of 512 byte sectors>
           Start offset in the backend device in 512-byte sectors. This
           option is only relevant for the encrypt mode.

           The --offset option sets the data offset (payload) of data
           device and must be aligned to 4096-byte sectors (must be
           multiple of 8). This option cannot be combined with
           --align-payload option.

       --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. Data beyond
           --device-size limit may be lost after operation gets

           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).

       --pbkdf <PBKDF spec>
           Set Password-Based Key Derivation Function (PBKDF) algorithm
           for LUKS keyslot. The PBKDF can be: pbkdf2 (for PBKDF2
           according to RFC2898), argon2i for Argon2i or argon2id for
           Argon2id (see Argon2
           <> for more info).

           For LUKS1, only PBKDF2 is accepted (no need to use this
           option). The default PBKDF for LUKS2 is set during
           compilation time and is available in cryptsetup --help

           A PBKDF is used for increasing dictionary and brute-force
           attack cost for keyslot passwords. The parameters can be
           time, memory and parallel cost.

           For PBKDF2, only time cost (number of iterations) applies.
           For Argon2i/id, there is also memory cost (memory required
           during the process of key derivation) and parallel cost
           (number of threads that run in parallel during the key

           Note that increasing memory cost also increases time, so the
           final parameter values are measured by a benchmark. The
           benchmark tries to find iteration time (--iter-time) with
           required memory cost --pbkdf-memory. If it is not possible,
           the memory cost is decreased as well. The parallel cost
           --pbkdf-parallel is constant and is checked against available
           CPU cores.

           You can see all PBKDF parameters for particular LUKS2 keyslot
           with cryptsetup-luksDump(8) command.

           NOTE: If you do not want to use benchmark and want to specify
           all parameters directly, use --pbkdf-force-iterations with
           --pbkdf-memory and --pbkdf-parallel. This will override the
           values without benchmarking. Note it can cause extremely long
           unlocking time. Use only in specific cases, for example, if
           you know that the formatted device will be used on some small
           embedded system.

           MINIMAL AND MAXIMAL PBKDF COSTS: For PBKDF2, the minimum
           iteration count is 1000 and maximum is 4294967295 (maximum
           for 32bit unsigned integer). Memory and parallel costs are
           unused for PBKDF2. For Argon2i and Argon2id, minimum
           iteration count (CPU cost) is 4 and maximum is 4294967295
           (maximum for 32bit unsigned integer). Minimum memory cost is
           32 KiB and maximum is 4 GiB. (Limited by addressable memory
           on some CPU platforms.) If the memory cost parameter is
           benchmarked (not specified by a parameter) it is always in
           range from 64 MiB to 1 GiB. The parallel cost minimum is 1
           and maximum 4 (if enough CPUs cores are available, otherwise
           it is decreased).

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

       --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.

       --pbkdf-force-iterations <num>
           Avoid PBKDF benchmark and set time cost (iterations)
           directly. It can be used for LUKS/LUKS2 device only. See
           --pbkdf option for more info.

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

           Prints progress data in JSON format suitable mostly for
           machine processing. It prints separate line every half second
           (or based on --progress-frequency value). The JSON output
           looks as follows during progress (except it’s compact single

                 "device":"/dev/sda"       // backing device or file
                 "device_bytes":"8192",    // bytes of I/O so far
                 "device_size":"44040192", // total bytes of I/O to go
                 "speed":"126877696",      // calculated speed in bytes per second (based on progress so far)
                 "eta_ms":"2520012"        // estimated time to finish an operation in milliseconds
                 "time_ms":"5561235"       // total time spent in IO operation in milliseconds

           Note on numbers in JSON output: Due to JSON parsers
           limitations all numbers are represented in a string format
           due to need of full 64bit unsigned integers.

       --timeout, -t <number of seconds>
           The number of seconds to wait before timeout on passphrase
           input via terminal. It is relevant every time a passphrase is
           asked. It has no effect if used in conjunction with

           This option is useful when the system should not stall if the
           user does not input a passphrase, e.g. during boot. The
           default is a value of 0 seconds, which means to wait forever.

       --tries, -T
           How often the input of the passphrase shall be retried. The
           default is 3 tries.

       --align-payload <number of 512 byte sectors>
           Align payload at a boundary of value 512-byte sectors.

           If not specified, cryptsetup tries to use the topology info
           provided by the kernel for the underlying device to get the
           optimal alignment. If not available (or the calculated value
           is a multiple of the default) data is by default aligned to a
           1MiB boundary (i.e. 2048 512-byte sectors).

           For a detached LUKS header, this option specifies the offset
           on the data device. See also the --header option.

           WARNING: This option is DEPRECATED and has often unexpected
           impact to the data offset and keyslot area size (for LUKS2)
           due to the complex rounding. For fixed data device offset use
           --offset option instead.

       --uuid <UUID>
           When used in encryption mode use the provided UUID for the
           new LUKS header instead of generating a new one.

           LUKS1 (only in decryption mode): To find out what UUID to
           pass look for temporary files LUKS-UUID.[|log|org|new] of the
           interrupted decryption process.

           The UUID must be provided in the standard UUID format, e.g.

       --header <device or file storing the LUKS header>
           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.

           If used with --encrypt/--new option, the header file will be
           created (or overwritten). Use with care.

           LUKS2: For decryption mode the option may be used to export
           original LUKS2 header to a detached file. The passed future
           file must not exist at the time of initializing the
           decryption operation. This frees space in head of data device
           so that data can be moved at original LUKS2 header location.
           Later on decryption operation continues as if the ordinary
           detached header was passed.

           WARNING: Never put exported header file in a filesystem on
           top of device you are about to decrypt! It would cause a

       --force-offline-reencrypt (LUKS2 only)
           Bypass active device auto-detection and enforce offline

           This option is useful especially for reencryption of LUKS2
           images put in files (auto-detection is not reliable in this

           It may also help in case active device auto-detection on
           particular data device does not work or report errors.

           WARNING: Use with extreme caution! This may destroy data if
           the device is activated and/or actively used.

           Do not use password quality checking for new LUKS passwords.

           This option is ignored if cryptsetup is built without
           password quality checking support.

           For more info about password quality check, see the manual
           page for pwquality.conf(5) and passwdqc.conf(5).

           Disable lock protection for metadata on disk. This option is
           valid only for LUKS2 and ignored for other formats.

           NOTE: With locking disabled LUKS2 images in files can be
           fully (re)encrypted offline without need for super user
           privileges provided used block ciphers are available in
           crypto backend.

           WARNING: Do not use this option unless you run cryptsetup in
           a restricted environment where locking is impossible to
           perform (where /run directory cannot be used).

           Do not load volume key in kernel keyring and store it
           directly in the dm-crypt target instead. This option is
           supported only for the LUKS2 type.

       --sector-size bytes (LUKS2 only)
           Reencrypt device with new encryption sector size enforced.

           WARNING: Increasing encryption sector size may break hosted
           filesystem. Do not run reencryption with
           --force-offline-reencrypt if unsure what block size was
           filesystem formatted with.

       --label <LABEL> --subsystem <SUBSYSTEM>
           Set label and subsystem description for LUKS2 device. The
           label and subsystem are optional fields and can be later used
           in udev scripts for triggering user actions once the device
           marked by these labels is detected.

       --luks2-metadata-size <size>
           This option can be used to enlarge the LUKS2 metadata (JSON)
           area. The size includes 4096 bytes for binary metadata
           (usable JSON area is smaller of the binary area). According
           to LUKS2 specification, only these values are valid: 16, 32,
           64, 128, 256, 512, 1024, 2048 and 4096 kB The <size> can be
           specified with unit suffix (for example 128k).

       --luks2-keyslots-size <size>
           This option can be used to set specific size of the LUKS2
           binary keyslot area (key material is encrypted there). The
           value must be aligned to multiple of 4096 bytes with maximum
           size 128MB. The <size> can be specified with unit suffix (for
           example 128k).

       --keyslot-cipher <cipher-spec>
           This option can be used to set specific cipher encryption for
           the LUKS2 keyslot area.

       --keyslot-key-size <bits>
           This option can be used to set specific key size for the
           LUKS2 keyslot area.

       --encrypt, --new, -N
           Initialize (and run) device in-place encryption mode.

           Initialize (and run) device decryption mode.

       --init-only (LUKS2 only)
           Initialize reencryption (any mode) operation in LUKS2
           metadata only and exit. If any reencrypt operation is already
           initialized in metadata, the command with --init-only
           parameter fails.

       --resume-only (LUKS2 only)
           Resume reencryption (any mode) operation already described in
           LUKS2 metadata. If no reencrypt operation is initialized, the
           command with --resume-only parameter fails. Useful for
           resuming reencrypt operation without accidentally triggering
           new reencryption operation.

       --resilience mode (LUKS2 only)
           Reencryption resilience mode can be one of checksum, journal
           or none.

           checksum: default mode, where individual checksums of
           ciphertext hotzone sectors are stored, so the recovery
           process can detect which sectors were already reencrypted. It
           requires that the device sector write is atomic.

           journal: the hotzone is journaled in the binary area (so the
           data are written twice).

           none: performance mode. There is no protection and the only
           way it’s safe to interrupt the reencryption is similar to old
           offline reencryption utility.

           Resilience modes can be changed unless datashift mode is used
           for operation initialization (encryption with
           --reduce-device-size option)

       --resilience-hash hash (LUKS2 only)
           The hash algorithm used with "--resilience checksum" only.
           The default hash is sha256. With other resilience modes, the
           hash parameter is ignored.

       --hotzone-size size (LUKS2 only)
           This option can be used to set an upper limit on the size of
           reencryption area (hotzone). The size can be specified with
           unit suffix (for example 50M). Note that actual hotzone size
           may be less than specified <size> due to other limitations
           (free space in keyslots area or available memory).

           With decryption mode for devices with LUKS2 header placed in
           head of data device, the option specifies how large is the
           first data segment moved from original data offset pointer.

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

           It could be useful if you added some space to underlying
           partition or logical volume (so last size sectors contains no

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

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

           LUKS2: Initialize LUKS2 reencryption with data device size
           reduction (currently only encryption mode is supported).

           Recommended minimal size is twice the default LUKS2 header
           size (--reduce-device-size 32M) for encryption mode.

           LUKS1: Enlarge data offset to specified value by shrinking
           device size.

           You cannot shrink device more than by 64 MiB (131072

       --batch-mode, -q
           Suppresses all confirmation questions. Use with care!

           If the --verify-passphrase option is not specified, this
           option also switches off the passphrase verification.

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

           If --debug-json is used, additional LUKS2 JSON data
           structures are printed.

       --version, -V
           Show the program version.

           Show short option help.

       --help, -?
           Show help text and default parameters.

EXAMPLES         top

       NOTE: You may drop --type luks2 option as long as LUKS2 format is

       Encrypt LUKS2 device (in-place). Make sure last 32 MiB on
       /dev/plaintext is unused (e.g.: does not contain filesystem

       cryptsetup reencrypt --encrypt --type luks2 --reduce-device-size
       32m /dev/plaintext_device

       Encrypt LUKS2 device (in-place) with detached header put in a

       cryptsetup reencrypt --encrypt --type luks2 --header
       my_luks2_header /dev/plaintext_device

       Initialize LUKS2 in-place encryption operation only and activate
       the device (not yet encrypted):

       cryptsetup reencrypt --encrypt --type luks2 --init-only
       --reduce-device-size 32m /dev/plaintext_device

       Resume online encryption on device initialized in example above:

       cryptsetup reencrypt --resume-only /dev/plaintext_device or
       cryptsetup reencrypt --active-name my_future_luks_device

       Reencrypt LUKS2 device (refresh volume key only):

       cryptsetup reencrypt /dev/encrypted_device

       Decrypt LUKS2 device with header put in head of data device
       (header file does not exist):

       cryptsetup reencrypt --decrypt --header /export/header/to/file

       Decrypt LUKS2 device with detached header (header file exists):

       cryptsetup reencrypt --decrypt --header detached-luks2-header

       Resume interrupted LUKS2 decryption:

       cryptsetup reencrypt --resume-only --header luks2-hdr-file

REPORTING BUGS         top

       Report bugs at cryptsetup mailing list
       <> or in Issues project section

       Please attach output of the failed command with --debug option

SEE ALSO         top

       Cryptsetup FAQ

       cryptsetup(8), integritysetup(8) and veritysetup(8)

CRYPTSETUP         top

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cryptsetup 2.6.1-git           2022-12-14        CRYPTSETUP-REENCRYPT(8)

Pages that refer to this page: cryptsetup(8)