Values can be between 1 and 64 MiB.

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

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).

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.

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.

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

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

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.

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.

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.

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).

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. 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).

{


  "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.

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.

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.

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.

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.

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.

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).

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).

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.

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)

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.

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).

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

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