Provided by: cryptsetup-bin_2.5.0-2ubuntu1_amd64 
NAME
cryptsetup - manage plain dm-crypt, LUKS, and other encrypted volumes
SYNOPSIS
cryptsetup <action> [<options>] <action args>
DESCRIPTION
cryptsetup is used to conveniently setup dm-crypt managed device-mapper mappings. These
include plain dm-crypt volumes and LUKS volumes. The difference is that LUKS uses a
metadata header and can hence offer more features than plain dm-crypt. On the other hand,
the header is visible and vulnerable to damage.
In addition, cryptsetup provides limited support for the use of loop-AES volumes,
TrueCrypt, VeraCrypt, and BitLocker compatible volumes.
For more information about specific cryptsetup action see cryptsetup-<action>(8), where
<action> is the name of the cryptsetup action.
BASIC ACTIONS
The following are valid actions for all supported device types.
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).
PLAIN MODE
Plain dm-crypt encrypts the device sector-by-sector with a single, non-salted hash of the
passphrase. No checks are performed, no metadata is used. There is no formatting
operation. When the raw device is mapped (opened), the usual device operations can be used
on the mapped device, including filesystem creation. Mapped devices usually reside in
/dev/mapper/<name>.
The following are valid plain device type actions:
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).
LUKS EXTENSION
LUKS, the Linux Unified Key Setup, is a standard for disk encryption. It adds a
standardized header at the start of the device, a key-slot area directly behind the header
and the bulk data area behind that. The whole set is called a 'LUKS container'. The device
that a LUKS container resides on is called a 'LUKS device'. For most purposes, both terms
can be used interchangeably. But note that when the LUKS header is at a nonzero offset in
a device, then the device is not a LUKS device anymore, but has a LUKS container stored in
it at an offset.
LUKS can manage multiple passphrases that can be individually revoked or changed and that
can be securely scrubbed from persistent media due to the use of anti-forensic stripes.
Passphrases are protected against brute-force and dictionary attacks by Password-Based Key
Derivation Function (PBKDF).
LUKS2 is a new version of header format that allows additional extensions like different
PBKDF algorithm or authenticated encryption. You can format device with LUKS2 header if
you specify --type luks2 in luksFormat command. For activation, the format is already
recognized automatically.
Each passphrase, also called a key in this document, is associated with one of 8
key-slots. Key operations that do not specify a slot affect the first slot that matches
the supplied passphrase or the first empty slot if a new passphrase is added.
The <device> parameter can also be specified by a LUKS UUID in the format UUID=<uuid>.
Translation to real device name uses symlinks in /dev/disk/by-uuid directory.
To specify a detached header, the --header parameter can be used in all LUKS commands and
always takes precedence over the positional <device> parameter.
The following are valid LUKS actions:
FORMAT
luksFormat <device> [<key file>]
Initializes a LUKS partition and sets the initial passphrase (for key-slot 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> <key slot number>
Wipe the key-slot number <key slot> 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).
LOOP-AES EXTENSION
cryptsetup supports mapping loop-AES encrypted partition using a compatibility mode.
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.
TCRYPT (TRUECRYPT AND VERACRYPT COMPATIBLE) EXTENSION
cryptsetup supports mapping of TrueCrypt, tcplay or VeraCrypt encrypted partition using a
native Linux kernel API. Header formatting and TCRYPT header change is not supported,
cryptsetup never changes TCRYPT header on-device.
TCRYPT extension requires kernel userspace crypto API to be available (introduced in Linux
kernel 2.6.38). If you are configuring kernel yourself, enable "User-space interface for
symmetric key cipher algorithms" in "Cryptographic API" section (CRYPTO_USER_API_SKCIPHER
.config option).
Because TCRYPT header is encrypted, you have to always provide valid passphrase and
keyfiles.
Cryptsetup should recognize all header variants, except legacy cipher chains using LRW
encryption mode with 64 bits encryption block (namely Blowfish in LRW mode is not
recognized, this is limitation of kernel crypto API).
VeraCrypt is extension of TrueCrypt header with increased iteration count so unlocking can
take quite a lot of time.
To open a VeraCrypt device with a custom Personal Iteration Multiplier (PIM) value, use
either the --veracrypt-pim=<PIM> option to directly specify the PIM on the command- line
or use --veracrypt-query-pim to be prompted for the PIM.
The PIM value affects the number of iterations applied during key derivation. Please refer
to PIM <https://www.veracrypt.fr/en/Personal%20Iterations%20Multiplier%20%28PIM%29.html>
for more detailed information.
If you need to disable VeraCrypt device support, use --disable-veracrypt option.
NOTE: Activation with tcryptOpen is supported only for cipher chains using LRW or XTS
encryption modes.
The tcryptDump command should work for all recognized TCRYPT devices and doesn’t require
superuser privilege.
To map system device (device with boot loader where the whole encrypted system resides)
use --tcrypt-system option. You can use partition device as the parameter (parameter must
be real partition device, not an image in a file), then only this partition is mapped.
If you have the whole TCRYPT device as a file image and you want to map multiple partition
encrypted with system encryption, please create loopback mapping with partitions first
(losetup -P, see losetup(8) man page for more info), and use loop partition as the device
parameter.
If you use the whole base device as a parameter, one device for the whole system
encryption is mapped. This mode is available only for backward compatibility with older
cryptsetup versions which mapped TCRYPT system encryption using the whole device.
To use hidden header (and map hidden device, if available), use --tcrypt-hidden option.
To explicitly use backup (secondary) header, use --tcrypt-backup option.
NOTE: There is no protection for a hidden volume if the outer volume is mounted. The
reason is that if there were any protection, it would require some metadata describing
what to protect in the outer volume and the hidden volume would become detectable.
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.
BITLK (WINDOWS BITLOCKER COMPATIBLE) EXTENSION
cryptsetup supports mapping of BitLocker and BitLocker to Go encrypted partition using a
native Linux kernel API. Header formatting and BITLK header changes are not supported,
cryptsetup never changes BITLK header on-device.
BITLK extension requires kernel userspace crypto API to be available (for details see
TCRYPT section).
Cryptsetup should recognize all BITLK header variants, except legacy header used in
Windows Vista systems and partially decrypted BitLocker devices. Activation of legacy
devices encrypted in CBC mode requires at least Linux kernel version 5.3 and for devices
using Elephant diffuser kernel 5.6.
The bitlkDump command should work for all recognized BITLK devices and doesn’t require
superuser privilege.
For unlocking with the open a password or a recovery passphrase or a startup key must be
provided.
Additionally unlocking using volume key is supported. You must provide BitLocker Full
Volume Encryption Key (FVEK) using the --volume-key-file option. The key must be decrypted
and without the header (only 128/256/512 bits of key data depending on used cipher and
mode).
Other unlocking methods (TPM, SmartCard) are not supported.
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.
MISCELLANEOUS ACTIONS
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).
PLAIN DM-CRYPT OR LUKS?
Unless you understand the cryptographic background well, use LUKS. With plain dm-crypt
there are a number of possible user errors that massively decrease security. While LUKS
cannot fix them all, it can lessen the impact for many of them.
WARNINGS
A lot of good information on the risks of using encrypted storage, on handling problems
and on security aspects can be found in the Cryptsetup FAQ. Read it. Nonetheless, some
risks deserve to be mentioned here.
Backup: Storage media die. Encryption has no influence on that. Backup is mandatory for
encrypted data as well, if the data has any worth. See the Cryptsetup FAQ for advice on
how to do a backup of an encrypted volume.
Character encoding: If you enter a passphrase with special symbols, the passphrase can
change depending on character encoding. Keyboard settings can also change, which can make
blind input hard or impossible. For example, switching from some ASCII 8-bit variant to
UTF-8 can lead to a different binary encoding and hence different passphrase seen by
cryptsetup, even if what you see on the terminal is exactly the same. It is therefore
highly recommended to select passphrase characters only from 7-bit ASCII, as the encoding
for 7-bit ASCII stays the same for all ASCII variants and UTF-8.
LUKS header: If the header of a LUKS volume gets damaged, all data is permanently lost
unless you have a header-backup. If a key-slot is damaged, it can only be restored from a
header-backup or if another active key-slot with known passphrase is undamaged. Damaging
the LUKS header is something people manage to do with surprising frequency. This risk is
the result of a trade-off between security and safety, as LUKS is designed for fast and
secure wiping by just overwriting header and key-slot area.
Previously used partitions: If a partition was previously used, it is a very good idea to
wipe filesystem signatures, data, etc. before creating a LUKS or plain dm-crypt container
on it. For a quick removal of filesystem signatures, use wipefs(8). Take care though that
this may not remove everything. In particular, MD RAID signatures at the end of a device
may survive. It also does not remove data. For a full wipe, overwrite the whole partition
before container creation. If you do not know how to do that, the cryptsetup FAQ describes
several options.
EXAMPLES
Example 1: Create LUKS 2 container on block device /dev/sdX.
sudo cryptsetup --type luks2 luksFormat /dev/sdX
Example 2: Add an additional passphrase to key slot 5.
sudo cryptsetup luksAddKey --key-slot 5 /dev/sdX
Example 3: Create LUKS header backup and save it to file.
sudo cryptsetup luksHeaderBackup /dev/sdX --header-backup-file
/var/tmp/NameOfBackupFile
Example 4: Open LUKS container on /dev/sdX and map it to sdX_crypt.
sudo cryptsetup open /dev/sdX sdX_crypt
WARNING: The command in example 5 will erase all key slots.
Your cannot use your LUKS container afterward anymore unless you have a backup to
restore.
Example 5: Erase all key slots on /dev/sdX.
sudo cryptsetup erase /dev/sdX
Example 6: Restore LUKS header from backup file.
sudo cryptsetup luksHeaderRestore /dev/sdX --header-backup-file
/var/tmp/NameOfBackupFile
RETURN CODES
Cryptsetup returns 0 on success and a non-zero value on error.
Error codes are: 1 wrong parameters, 2 no permission (bad passphrase), 3 out of memory, 4
wrong device specified, 5 device already exists or device is busy.
NOTES
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 for the maximum key file size and can be overwritten using
--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 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.
WARNING: 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 for the maximum key file size and
can be overwritten using --keyfile-size option.
Passphrase processing for LUKS
LUKS uses PBKDF to protect against dictionary attacks and to give some protection to
low-entropy passphrases (see cryptsetup FAQ).
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.
Passphrase processing: Whenever a passphrase is added to a LUKS header (luksAddKey,
luksFormat), the user may specify how much the 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 open 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 in order 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 an encrypted partition is unlocked. The behavior
of plain dm-crypt is different. It will always decrypt with the passphrase given. If the
given passphrase is wrong, the device mapped by plain dm-crypt will essentially still
contain encrypted data and 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 in order to get more options.
For the --hash option, if the crypto backend is libgcrypt, then all algorithms supported
by the gcrypt library are available. For other crypto backends, some algorithms may be
missing.
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 (RNG) used in cryptsetup are always the kernel RNGs without any
modifications or additions to data stream produced.
There are two types of randomness cryptsetup/LUKS needs. One type (which always uses
/dev/urandom) is used for salts, the AF splitter and for wiping deleted keyslots.
The second type is used for the volume key. You can switch between using /dev/random and
/dev/urandom here, see --use-random and --use-urandom options. Using /dev/random on a
system without enough entropy sources can cause luksFormat to block until the requested
amount of random data is gathered. In a low-entropy situation (embedded system), this can
take a very long time and potentially forever. At the same time, using /dev/urandom in a
low-entropy situation will produce low-quality keys. This is a serious problem, but
solving it is out of scope for a mere man-page. See urandom(4) for more information.
Authenticated disk encryption (EXPERIMENTAL)
Since Linux kernel version 4.12 dm-crypt supports authenticated disk encryption.
Normal disk encryption modes are length-preserving (plaintext sector is of the same size
as a ciphertext sector) and can provide only confidentiality protection, but not
cryptographically sound data integrity protection.
Authenticated modes require additional space per-sector for authentication tag and use
Authenticated Encryption with Additional Data (AEAD) algorithms.
If you configure LUKS2 device with data integrity protection, there will be an underlying
dm-integrity device, which provides additional per-sector metadata space and also provide
data journal protection to ensure atomicity of data and metadata update. 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 LUKS2 device with
data integrity protection, use --integrity option.
Since dm-integrity doesn’t support discards (TRIM), dm-crypt device on top of it inherits
this, so integrity protection mode doesn’t support discards either.
Some integrity modes requires two independent keys (key for encryption and for
authentication). Both these keys are stored in one LUKS keyslot.
WARNING: All support for authenticated modes is experimental and there are only some modes
available for now. Note that there are a very few authenticated encryption algorithms that
are suitable for disk encryption. You also cannot use CRC32 or any 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. This mode requires Linux kernel 2.6.25 or more recent which
supports the loop autoclear flag (loop device is cleared on the last close automatically).
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 proper atomic
update, there is a locking mechanism. For an image in file, code uses 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>.
AUTHORS
Cryptsetup is originally written by Jana Saout <jana@saout.de>.
The LUKS extensions and original man page were written by Clemens Fruhwirth
<clemens@endorphin.org>.
Man page extensions by Milan Broz <gmazyland@gmail.com>.
Man page rewrite and extension by Arno Wagner <arno@wagner.name>.
REPORTING BUGS
Report bugs at cryptsetup mailing list <cryptsetup@lists.linux.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/>.