The hash algorithm must provide at least 160 bits of output. Do not use a non-crypto hash like xxhash as this breaks security. Use cryptsetup --help to show the defaults.

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.

See section NOTES ON PASSPHRASE PROCESSING in cryptsetup(8) for more information.

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

See NOTES ON RANDOM NUMBER GENERATORS in cryptsetup(8) for more information. Use cryptsetup --help to show the compiled-in default random number generator.

WARNING: In a low-entropy situation (e.g. in an embedded system) and older kernels, both selections are problematic. Using /dev/urandom can lead to weak keys. Using /dev/random can block a long time, potentially forever, if not enough entropy can be harvested by the kernel.

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.

This option can be used for open --type plain or luksFormat. All other LUKS actions will use the key-size specified in the LUKS header. Use cryptsetup --help to show the compiled-in defaults.

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.

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.

The UUID must be provided in the standard UUID format, e.g. 12345678-1234-1234-1234-123456789abc.

With a file name as the argument to --header, the file will be automatically created if it does not exist. See the cryptsetup FAQ for header size calculation.

The --align-payload option is taken as absolute sector alignment on ciphertext device and can be zero.

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).

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).

For LUKS2 devices it’s established based on parameters provided by underlying data device. For native 4K block devices it’s 4096 bytes. For 4K/512e (4K physical sector size with 512 bytes emulation) it’s 4096 bytes. For drives reporting only 512 bytes block size it remains 512 bytes. If data device is regular file put in filesystem it’s 4096 bytes.

Note that if sector size is higher than underlying device hardware sector and there is not integrity protection that uses data journal, using this option can increase risk on incomplete sector writes during a power fail.

If used together with --integrity option and dm-integrity journal, the atomicity of writes is guaranteed in all cases (but it cost write performance - data has to be written twice).

Increasing sector size from 512 bytes to 4096 bytes can provide better performance on most of the modern storage devices and also with some hw encryption accelerators.

WARNING: This extension is EXPERIMENTAL and requires dm-integrity kernel target (available since kernel version 4.12). For native AEAD modes, also enable "User-space interface for AEAD cipher algorithms" in "Cryptographic API" section (CONFIG_CRYPTO_USER_API_AEAD .config option).

For more info, see AUTHENTICATED DISK ENCRYPTION section in cryptsetup(8).

WARNING: Do not use this option until you need compatibility with specific old kernel.

NOTE: Even some writes to the device can fail if the write is not aligned to page size and page-cache initiates read of a sector with invalid integrity tag.

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.