OPEN¶

open <device> <name> --type <device_type>

Opens (creates a mapping with) <name> backed by device <device>. See cryptsetup-open(8).

CLOSE¶

close <name>

Removes the existing mapping <name> and wipes the key from kernel memory. See cryptsetup-close(8).

STATUS¶

status <name>

Reports the status for the mapping <name>. See cryptsetup-status(8).

RESIZE¶

resize <name>

Resizes an active mapping <name>. See cryptsetup-resize(8).

REFRESH¶

refresh <name>

Refreshes parameters of active mapping <name>. See cryptsetup-refresh(8).

REENCRYPT¶

reencrypt <device> or --active-name <name> [<new_name>]

Run LUKS device reencryption. See cryptsetup-reencrypt(8).

OPEN¶

open --type plain <device> <name>
create <name> <device> (OBSOLETE syntax)

Opens (creates a mapping with) <name> backed by device <device>. See cryptsetup-open(8).

FORMAT¶

luksFormat <device> [<key file>]

Initializes a LUKS partition and sets the initial passphrase (for keyslot 0). See cryptsetup-luksFormat(8).

OPEN¶

open --type luks <device> <name>
luksOpen <device> <name> (old syntax)

Opens the LUKS device <device> and sets up a mapping <name> after successful verification of the supplied passphrase. See cryptsetup-open(8).

SUSPEND¶

luksSuspend <name>

Suspends an active device (all IO operations will block and accesses to the device will wait indefinitely) and wipes the encryption key from kernel memory. See cryptsetup-luksSuspend(8).

RESUME¶

luksResume <name>

Resumes a suspended device and reinstates the encryption key. See cryptsetup-luksResume(8).

ADD KEY¶

luksAddKey <device> [<key file with new key>]

Adds a new passphrase using an existing passphrase. See cryptsetup-luksAddKey(8).

REMOVE KEY¶

luksRemoveKey <device> [<key file with passphrase to be removed>]

Removes the supplied passphrase from the LUKS device. See cryptsetup-luksRemoveKey(8).

CHANGE KEY¶

luksChangeKey <device> [<new key file>]

Changes an existing passphrase. See cryptsetup-luksChangeKey(8).

CONVERT KEY¶

luksConvertKey <device>

Converts an existing LUKS2 keyslot to new PBKDF parameters. See cryptsetup-luksConvertKey(8).

KILL SLOT¶

luksKillSlot <device> <number>

Wipe the keyslot with the <number> from the LUKS device. See cryptsetup-luksKillSlot(8).

ERASE¶

erase <device>
luksErase <device> (old syntax)

Erase all keyslots and make the LUKS container permanently inaccessible. See cryptsetup-erase(8).

UUID¶

luksUUID <device>

Print or set the UUID of a LUKS device. See cryptsetup-luksUUID(8).

IS LUKS¶

isLuks <device>

Returns true, if <device> is a LUKS device, false otherwise. See cryptsetup-isLuks(8).

DUMP¶

luksDump <device>

Dump the header information of a LUKS device. See cryptsetup-luksDump(8).

HEADER BACKUP¶

luksHeaderBackup <device> --header-backup-file <file>

Stores a binary backup of the LUKS header and keyslot area. See cryptsetup-luksHeaderBackup(8).

HEADER RESTORE¶

luksHeaderRestore <device> --header-backup-file <file>

Restores a binary backup of the LUKS header and keyslot area from the specified file. See cryptsetup-luksHeaderRestore(8).

TOKEN¶

token <add|remove|import|export> <device>

Manipulate token objects used for obtaining passphrases. See cryptsetup-token(8).

CONVERT¶

convert <device> --type <format>

Converts the device between LUKS1 and LUKS2 format (if possible). See cryptsetup-convert(8).

CONFIG¶

config <device>

Set permanent configuration options (store to LUKS header). See cryptsetup-config(8).

OPEN¶

open --type loopaes <device> <name> --key-file <keyfile>
loopaesOpen <device> <name> --key-file <keyfile> (old syntax)

Opens the loop-AES <device> and sets up a mapping <name>. See cryptsetup-open(8).

See also section 7 of the FAQ and loop-AES <http://loop-aes.sourceforge.net> for more information regarding loop-AES.

OPEN¶

open --type tcrypt <device> <name>
tcryptOpen_ <device> <name> (old syntax)

Opens the TCRYPT (a TrueCrypt-compatible) <device> and sets up a mapping <name>. See cryptsetup-open(8).

DUMP¶

tcryptDump <device>

Dump the header information of a TCRYPT device. See cryptsetup-tcryptDump(8).

See also TrueCrypt <https://en.wikipedia.org/wiki/TrueCrypt> and VeraCrypt <https://en.wikipedia.org/wiki/VeraCrypt> pages for more information.

Please note that cryptsetup does not use TrueCrypt or VeraCrypt code; please report all problems related to this compatibility extension to the cryptsetup project.

OPEN¶

open --type bitlk <device> <name>
bitlkOpen <device> <name> (old syntax)

Opens the BITLK (a BitLocker-compatible) <device> and sets up a mapping <name>. See cryptsetup-open(8).

DUMP¶

bitlkDump <device>

Dump the header information of a BITLK device. See cryptsetup-bitlkDump(8).

Please note that cryptsetup does not use any Windows BitLocker code; please report all problems related to this compatibility extension to the cryptsetup project.

OPEN¶

open --type fvault2 <device> <name>
fvault2Open <device> <name> (old syntax)

Opens the FVAULT2 (a FileVault2-compatible) <device> (usually the second partition on the device) and sets up a mapping <name>. See cryptsetup-open(8).

FORMAT¶

luksFormat --type luks2 --hw-opal <device> [<key file>]

Additionally specify --hw-opal-only instead of --hw-opal to avoid the dm-crypt layer. Other than the usual passphrase, an admin password will have to be specified when formatting the drive’s first partition, and will have to be re-supplied when formatting any other partition until a factory reset is performed.

ERASE¶

erase <device>

Securely erase a partition or device. Requires admin password. Additionally specify --hw-opal-factory-reset for a FULL factory reset of the drive, using the drive’s PSID (typically printed on the label) instead of the admin password.

PSID must be entered without dashes, spaces or underscores.

WARNING: A factory reset will cause ALL data on the device to be lost, regardless of the partition it is run on, if any, and regardless of any LUKS2 header backup.

REPAIR¶

repair <device>

Tries to repair the device metadata if possible. Currently supported only for LUKS device type. See cryptsetup-repair(8).

BENCHMARK¶

benchmark <options>

Benchmarks, ciphers and KDF (key derivation function). See cryptsetup-benchmark(8).

Passphrase processing for PLAIN mode¶

Note that no iterated hashing or salting is done in plain mode. If hashing is done, it is a single direct hash. This means that low-entropy passphrases are easy to attack in plain mode.

From a terminal: The passphrase is read until the first newline, i.e., '\n'. The input without the newline character is processed with the default hash or the hash specified with --hash. The hash result will be truncated to the key size of the used cipher, or the size specified with -s.

From stdin: Reading will continue until a newline (or until the maximum input size is reached), with the trailing newline stripped. The maximum input size is defined by the same compiled-in default as the maximum key file size and can be overwritten using the --keyfile-size option.

The data read will be hashed with the default hash or the hash specified with --hash. The hash result will be truncated to the key size of the used cipher, or the size specified with -s.

Note that if --key-file=- is used for reading the key from stdin, trailing newlines are not stripped from the input.

If "plain" is used as an argument to --hash, the input data will not be hashed. Instead, it will be zero-padded (if shorter than the key size) or truncated (if longer than the key size) and used directly as the binary key. This is useful for directly specifying a binary key. No warning will be given if the amount of data read from stdin is less than the key size.

From a key file: It will be truncated to the key size of the used cipher or the size given by -s and directly used as a binary key.

The --hash argument is being ignored. The --hash option is usable only for stdin input in plain mode.

If the key file is shorter than the key, cryptsetup will quit with an error. The maximum input size is defined by the same compiled-in default as the maximum key file size and can be overwritten using the --keyfile-size option.

Passphrase processing for LUKS¶

From a terminal: The passphrase is read until the first newline and then processed by PBKDF2 without the newline character.

From stdin: LUKS will read passphrases from stdin up to the first newline character or the compiled-in maximum key file length. If --keyfile-size is given, it is ignored.

From key file: The complete keyfile is read up to the compiled-in maximum size. Newline characters do not terminate the input. The --keyfile-size option can be used to limit what is read.

LUKS uses Password-Based Key Derivation Function (PBKDF) to protect against brute-force attacks and to give some protection to low-entropy passphrases (see cryptsetup FAQ). LUKS1 supports the PBKDF2 algorithm only, while LUKS2 also supports memory-hard Argon2. PBKDFs are configured with costs: how long the iteration should run (CPU cost or iteration count), how much memory is used (memory cost), and how many parallel processes are used (parallel cost). PBKDF2 supports only iteration count. Cryptsetup uses PBKDF benchmarking to calculate optimal costs based on the computer where the new passphrase is being initialized. If needed, these costs can also be overwritten. Note that there are some hardcoded limits, for details see MINIMAL AND MAXIMAL PBKDF COSTS section in --pbkdf option description.

Whenever a passphrase is added to a LUKS header (luksAddKey, luksFormat), the user may specify how much time the passphrase processing should consume. The time is used to determine the iteration count for PBKDF2, and higher times will offer better protection for low-entropy passphrases, but the open command will take longer to complete. For passphrases that have entropy higher than the used key length, higher iteration times will not increase security.

The default setting of one or two seconds is sufficient for most practical cases. The only exception is a low-entropy passphrase used on a device with a slow CPU, as this will result in a low iteration count. On a slow device, it may be advisable to increase the iteration time using the --iter-time option to obtain a higher iteration count. This does slow down all later luksOpen operations accordingly.

Incoherent behavior for invalid passphrases/keys¶

LUKS checks for a valid passphrase when a keyslot is decrypted.

The behavior of plain dm-crypt is different. It will always unlock the device with the passphrase given. If the given passphrase is wrong, the device mapped by plain dm-crypt will use the wrong encryption key, and the data will be unreadable.

Supported ciphers, modes, hashes and key sizes¶

The available combinations of ciphers, modes, hashes and key sizes depend on kernel support. See /proc/crypto for a list of available options. You might need to load additional kernel crypto modules to get more options.

Cryptsetup processes many operations outside of the kernel, so the configured cryptographic library must also support selected algorithms. Some algorithms may be missing as cryptsetup can be compiled with various cryptographic backends (libraries).

Notes on passphrases¶

Mathematics can’t be bribed. Make sure you keep your passphrases safe. There are a few nice tricks for constructing a fallback when suddenly, out of the blue, your brain refuses to cooperate. These fallbacks need LUKS, as it’s only possible with LUKS to have multiple passphrases. Still, if your attacker model does not prevent it, storing your passphrase in a sealed envelope somewhere may be a good idea as well.

Notes on Random Number Generators¶

Random Number Generators (RNGs) used in cryptsetup are always the kernel RNGs without any modifications or additions to the data stream produced.

There are two types of randomness that cryptsetup/LUKS needs. One type is used for salts, the AF splitter and for wiping deleted keyslots. The second type is used for the volume key.

With recent kernels (Linux kernel 5.6), you do not need to worry about selecting RNG (/dev/random or /dev/urandom). In a low-entropy situation (embedded system), initialization of the kernel RNG can take a very long time, but this happens before cryptsetup can even be started. Use cryptsetup --help to show the compiled-in default random number generator. See urandom(4) for more information.

Authenticated disk encryption (EXPERIMENTAL)¶

Normal disk encryption modes are length-preserving (the plaintext sector is the same size as a ciphertext sector) and can provide only confidentiality protection, not cryptographically sound data integrity protection.

Authenticated modes require additional space per-sector for the authentication tag and use Authenticated Encryption with Additional Data (AEAD) algorithms.

If you configure a LUKS2 device with data integrity protection, there will be an underlying dm-integrity device, which provides additional per-sector metadata space and data journal protection to ensure atomicity of data and metadata updates. Because there must be additional space for metadata and journal, the available space for the device will be smaller than for length-preserving modes.

The dm-crypt device then resides on top of such a dm-integrity device. All activation and deactivation of this device stack is performed by cryptsetup; there is no difference in using luksOpen for integrity-protected devices. If you want to format a LUKS2 device with data integrity protection, use --integrity option (see cryptsetup-luksFormat(8)).

Albeit Linux kernel 5.7 added TRIM support for standalone dm-integrity devices, cryptsetup(8) can’t offer support for discards (TRIM) in authenticated encryption mode, because the underlying dm-crypt kernel module does not support this functionality when dm-integrity is used as auth tag space allocator (see --allow-discards in cryptsetup-open(8)).

Some integrity modes require two independent keys (a key for encryption and authentication). Both these keys are stored in one LUKS keyslot.

Support for authenticated modes is experimental, and only some modes are available now. Note that very few authenticated encryption algorithms are suitable for disk encryption. You also cannot use CRC32 or other non-cryptographic checksums (other than the special integrity mode "none"). If, for some reason, you want to have integrity control without using authentication mode, then you should separately configure dm-integrity independently of LUKS2.

Notes on loopback device use¶

Cryptsetup is usually used directly on a block device (disk partition or LVM volume). However, if the device argument is a file, cryptsetup tries to allocate a loopback device and map it into this file. Of course, you can always map a file to a loop device manually. See the cryptsetup FAQ for an example.

When device mapping is active, you can see the loop backing file in the status command output. Also see losetup(8).

LUKS2 header locking¶

The LUKS2 on-disk metadata is updated in several steps, and to achieve a proper atomic update, there is a locking mechanism. For an image in a file, the code uses the flock(2) system call. For a block device, lock is performed over a special file stored in a locking directory (by default /run/cryptsetup). The locking directory should be created with the proper security context by the distribution during the boot-up phase. Only LUKS2 uses locks; other formats do not use this mechanism.

LUKS on-disk format specification¶

For LUKS on-disk metadata specification, see LUKS1 <https://gitlab.com/cryptsetup/cryptsetup/wikis/Specification> and LUKS2 <https://gitlab.com/cryptsetup/LUKS2-docs>.