CRYPTSETUP(8) Maintenance Commands CRYPTSETUP(8)
NAME
cryptsetup - utility for configuring and managing encrypted storage
devices
SYNOPSIS
cryptsetup <action> [<options>] <action args>
DESCRIPTION
Cryptsetup is a utility for configuring and managing full-disk
encryption on storage devices. It can encrypt block devices (such as
hard drives or partitions) and containers (disk images stored as
files).
When you unlock an encrypted volume, cryptsetup creates a new device
mapping that applications can access like any regular storage device.
The actual encryption and decryption work is performed transparently by
the kernel’s device-mapper dm-crypt driver.
Cryptsetup works with two main volume types: plain encrypted volumes
and LUKS (Linux Unified Key Setup) volumes. Plain volumes provide
basic encryption, while LUKS volumes include a metadata header that
enables advanced features like multiple keyslots and key management.
Additionally, LUKS can be used to manage hardware-based encryption on
OPAL-capable storage drives.
Cryptsetup also provides limited support for volumes created by other
encryption systems, including loop-AES, TrueCrypt, VeraCrypt,
BitLocker, and FileVault2.
For more information about a specific cryptsetup action, see
cryptsetup-<action>(8), where <action> is the name of the cryptsetup
action.
Cryptsetup devices can be activated during boot through crypttab(5),
which is part of systemd(1) or other system init scripts.
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, and 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 keyslot
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.
LUKS can manage multiple passphrases that can be individually revoked
or changed. Each passphrase uses an individual keyslot containing a
volume key for data encryption. Keyslots can be securely scrubbed from
persistent media due to the use of anti-forensic stripes. Passphrases
are protected against brute-force attacks by the Password-Based Key
Derivation Function (PBKDF). A passphrase stored in a file is called a
key file. The only difference between a passphrase and a key file is
that a key file can contain binary data. Both are processed the same.
LUKS version 1 (or LUKS1) is the original metadata format, while LUKS2
is a new version that allows additional extensions like different PBKDF
algorithms or authenticated encryption. You can format the device with
a specific LUKS version with --type luks1 or --type luks2 in the
luksFormat command. Normally, you do not need to specify any version
as it is recognized automatically. The default format is LUKS2.
The <device> parameter can also be specified by a LUKS UUID in the
format UUID=<uuid>.
The LUKS header can be detached from data (stored separately). 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
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).
LOOP-AES EXTENSION
Cryptsetup supports mapping a 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 partitions using a native Linux kernel API. Header
formatting and TCRYPT header change are not supported; cryptsetup never
changes the TCRYPT header on-device.
TCRYPT extension requires the kernel userspace crypto API to be
available. If you are configuring the kernel yourself, enable
"User-space interface for symmetric key cipher algorithms" in
"Cryptographic API" section (CRYPTO_USER_API_SKCIPHER .config option).
Because the TCRYPT header is encrypted, you must always provide a valid
passphrase and keyfiles.
Cryptsetup should recognize all header variants, except legacy cipher
chains using LRW encryption mode with a 64-bit encryption block
(namely, Blowfish in LRW mode is not recognized; this is a limitation
of the kernel crypto API).
VeraCrypt is an extension of TrueCrypt with an 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://veracrypt.io/en/Personal%20Iterations%20Multiplier%20(PIM).html>
for more detailed information.
If you need to disable VeraCrypt device support, use
--disable-veracrypt option.
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 the system device (device with boot loader where the whole
encrypted system resides), use --tcrypt-system option. Please read
specific info in cryptsetup-tcryptOpen(8) --tcrypt-system option
section as mapping system-encrypted device is tricky.
To use a hidden header (and map hidden device, if available), use
--tcrypt-hidden option.
To explicitly use the backup (secondary) header, use --tcrypt-backup
option.
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
partitions using a native Linux kernel API. Header formatting and
BITLK header changes are not supported; cryptsetup never changes the
BITLK header on-device.
BITLK extension requires the kernel userspace crypto API to be
available (for details, see the TCRYPT section).
Cryptsetup should recognize all BITLK header variants, except the
legacy header used in Windows Vista systems and partially decrypted
BitLocker devices. Activation of legacy devices encrypted in CBC mode
requires at least a Linux kernel version 5.3, and for devices using the
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, a recovery passphrase, or a
startup key must be provided.
Additionally, unlocking using the 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 the 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.
FVAULT2 (APPLE MACOS FILEVAULT2 COMPATIBLE) EXTENSION
Cryptsetup supports the mapping of FileVault2 (FileVault2 full-disk
encryption) by Apple for the macOS operating system using a native
Linux kernel API.
Cryptsetup supports only FileVault2 based on Core Storage and HFS+
filesystem (introduced in MacOS X 10.7 Lion). It does NOT support the
new version of FileVault based on the APFS filesystem used in recent
macOS versions.
Header formatting and FVAULT2 header changes are not supported;
cryptsetup never changes the FVAULT2 header on-device.
FVAULT2 extension requires the kernel userspace crypto API to be
available (for details, see the TCRYPT section) and a kernel driver for
the HFS+ (hfsplus) filesystem.
Cryptsetup should recognize the basic configuration for portable
drives.
The fvault2Dump command should work for all recognized FVAULT2 devices
and doesn’t require superuser privilege.
For unlocking with the open, a password must be provided. Other
unlocking methods are not supported.
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).
SED (SELF ENCRYPTING DRIVE) OPAL EXTENSION
Cryptsetup supports using native hardware encryption on drives that
provide an OPAL interface, both nested with dm-crypt and standalone.
Passphrases, tokens and metadata are stored using the LUKS2 header
format, and are thus compatible with any software or system that uses
LUKS2 (e.g., tokens).
OPAL support requires at least kernel v6.4. Resizing devices is not
supported.
The --hw-opal can be specified for OPAL + dm-crypt, and --hw-opal-only
can be specified to use OPAL only, without a dm-crypt layer.
Opening, closing and enrolling tokens work the same way as with LUKS2
and dm-crypt. The new parameters are only necessary when formatting;
the LUKS2 metadata will ensure the right setup is performed when
opening or closing.
If no subsystem label is specified, it will be automatically set to
HW-OPAL so that it is immediately apparent when a device uses OPAL.
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.
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 MODE OR LUKS?
Unless you understand the cryptographic background well, use LUKS.
With plain mode, 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 back up 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 be changed, 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 a 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 keyslot is
damaged, it can only be restored from a header backup or if another
active keyslot with a known passphrase is undamaged. 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 the header and keyslot
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. For a quick removal of
filesystem signatures, use wipefs(8) with the --all option. Note that
it does not remove data; it only invalidates known format signatures.
For a full wipe, overwrite the whole partition before creating a
container. 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 keyslot 5.
sudo cryptsetup luksAddKey --key-slot 5 /dev/sdX
Example 3: Create LUKS header backup and save it to a 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 keyslots.
You cannot use your LUKS container afterward anymore unless you
have a backup to restore.
Example 5: Erase all keyslots 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 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>.
AUTHORS
Cryptsetup was 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 the 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 2.8.1 2025-08-13 CRYPTSETUP(8)
cryptsetup \- utility for configuring and managing encrypted storage devices