man > cryptsetup-reencrypt(8)

CRYPTSETUP-REENCRYPT(8)                 Maintenance Commands                 CRYPTSETUP-REENCRYPT(8)

NAME
       cryptsetup-reencrypt - reencrypt LUKS encrypted volumes in-place

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

DESCRIPTION
       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 parameter.

       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 unlocked 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 guarantees of confidentiality as part of the device contains plaintext.

       ALWAYS BE SURE YOU HAVE RELIABLE BACKUP BEFORE USING THIS ACTION ON LUKS DEVICE.

       <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].

LUKS2 REENCRYPTION
       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.

LUKS1 REENCRYPTION
       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
       --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 only.

           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 mode.

           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 specified.

           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 characters.

           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.

       --keep-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 used.

           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 option.

       --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 finished.

           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 <https://www.cryptolux.org/index.php/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 output.

           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 derivation.

           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 or cause
           out-of-memory conditions with unconditional process termination. 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.

       --progress-json
           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 line):

               {
                 "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
           --key-file.

           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.
           12345678-1234-1234-1234-123456789abc.

       --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 deadlock.

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

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

           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.

       --force-password
           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-blkid
           Disable use of blkid library for checking and wiping on-disk signatures.

       --disable-locks
           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).

       --disable-keyring
           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.

       --decrypt
           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 data).

           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 sectors).

       --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.

       --usage
           Show short option help.

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

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

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

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

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

       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 my_future_luks_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

   LUKS2 REENCRYPTION EXAMPLES
       Reencrypt LUKS2 device (refresh volume key only):

       cryptsetup reencrypt /dev/encrypted_device

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

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

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

       cryptsetup reencrypt --decrypt --header detached-luks2-header /dev/encrypted_device

       Resume interrupted LUKS2 decryption:

       cryptsetup reencrypt --resume-only --header luks2-hdr-file /dev/encrypted_device

REPORTING BUGS
       Report bugs at cryptsetup mailing list <cryptsetup AT lists.dev> or in Issues project
       section <https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.

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

SEE ALSO
       Cryptsetup FAQ <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>

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

CRYPTSETUP
       Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.

cryptsetup 2.7.0                             2024-11-14                      CRYPTSETUP-REENCRYPT(8)