cryptsetup-luksFormat(8) — Linux manual page

NAME \| SYNOPSIS \| DESCRIPTION \| OPTIONS \| REPORTING BUGS \| SEE ALSO \| CRYPTSETUP

CRYPTSETUP-LUKSFORMAT(8)   Maintenance Commands  CRYPTSETUP-LUKSFORMAT(8)

NAME top

       cryptsetup-luksFormat - initialize a LUKS partition and set the
       initial passphrase

SYNOPSIS top

       cryptsetup luksFormat [<options>] <device> [<key file>]

DESCRIPTION top

       Initializes a LUKS partition and sets the passphrase via prompting
       or <key file>. Note that if the second argument is present, the
       passphrase is taken from the file given there, without using the
       --key-file option. Also note that for both forms of reading the
       passphrase from a file, you can give '-' as a file name, which
       results in the passphrase being read from stdin and the safety
       question being skipped.

       You cannot call luksFormat on a device or filesystem that is
       mapped or in use, e.g., a mounted filesystem, used in LVM, active
       RAID member, etc. The device or filesystem has to be unmounted in
       order to call luksFormat.

       To enforce a specific version of LUKS format, use --type luks1 or
       type luks2. The default format is LUKS2.

       To use hardware encryption on an OPAL self-encrypting drive, use
       --hw-opal or --hw-opal-only. Note that some OPAL drives can
       require a PSID reset (with deletion of data) before using the LUKS
       format with OPAL options. See --hw-opal-factory-reset option in
       cryptsetup erase command.

       Doing a luksFormat on an existing LUKS container will regenerate
       the volume key. Unless you have a header backup, all old encrypted
       data in the container will be permanently irretrievable. Note that
       luksFormat does not wipe or overwrite the data area. It only
       creates a new LUKS header with fresh keyslots. See cryptsetup FAQ
       for more info on how to wipe the whole device, including encrypted
       data.

       <options> can be [--hash, --cipher, --verify-passphrase,
       --key-size, --key-slot, --key-file (takes precedence over optional
       second argument), --keyfile-offset, --keyfile-size, --use-random,
       --use-urandom, --uuid, --volume-key-file, --iter-time, --header,
       --pbkdf-force-iterations, --force-password, --disable-locks,
       --timeout, --type, --offset, --align-payload (DEPRECATED)].

       For LUKS2, additional <options> can be [--integrity,
       --integrity-no-wipe, --sector-size, --label, --subsystem, --pbkdf,
       --pbkdf-memory, --pbkdf-parallel, --disable-locks,
       --disable-keyring, --luks2-metadata-size, --luks2-keyslots-size,
       --keyslot-cipher, --keyslot-key-size, --integrity-legacy-padding,
       --hw-opal, --hw-opal-only].

OPTIONS top

--align-payload <number of 512 byte sectors> (DEPRECATED, use
--offset)
Align payload at a boundary of value 512-byte sectors.

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.

This option is DEPRECATED and has an unexpected impact on the
data offset and keyslot area size (for LUKS2) due to the
complex rounding. For fixed data device offset, use --offset
option instead.

--batch-mode, -q
Suppresses all confirmation questions. Use with care!

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

--cipher, -c <cipher-spec>
Set the cipher specification string.

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.

--debug or --debug-json
Run in debug mode with full diagnostic logs. Debug output
lines are always prefixed by #.

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

--disable-blkid
Disable use of the blkid library for checking and wiping
on-disk signatures.

--disable-keyring
Do not load the volume key in the kernel keyring; store it
directly in the dm-crypt target instead. This option is
supported only for the LUKS2 type.

--disable-locks
Disable lock protection for metadata on disk. This option is
valid only for LUKS2 and is ignored for other formats.

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).

--force-password
Do not use password quality checking for new LUKS passwords.

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).

--hash, -h <hash-spec>
Specifies the hash used in the LUKS key setup scheme and
volume key digest. The specified hash is used for PBKDF2 and
the AF splitter.

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.

--header <device or file storing the LUKS header>
Use a detached (separated) metadata device or file where the
LUKS header is stored. This option allows one to store the
ciphertext and LUKS header on different devices.

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 the ciphertext device and can be zero.

--help, -?
Show help text and default parameters.

--hw-opal
Format LUKS2 device with dm-crypt encryption stacked on top of
HW-based encryption configured on SED OPAL locking range. This
option enables both SW and HW based data encryption.

--hw-opal-only
Format LUKS2 device with HW based encryption configured on SED
OPAL locking range only. LUKS2 format only manages the locking
range unlock key. This option enables HW-based data encryption
managed by the SED OPAL drive only.

Please note that with OPAL-only (--hw-opal-only) encryption,
the configured OPAL administrator PIN (passphrase) allows
unlocking all configured locking ranges without LUKS keyslot
decryption (without knowledge of LUKS passphrase). Because of
many observed problems with compatibility, cryptsetup
currently DOES NOT use OPAL single-user mode, which would
allow such decoupling of OPAL admin PIN access.

--integrity <integrity algorithm>
Specify the integrity algorithm to be used for authenticated
disk encryption in LUKS2.

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

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

--integrity-inline
Store integrity tags in hardware sector integrity fields. The
device must support sectors with additional protection
information (PI, also known as DIF - data integrity field) of
the requested size. Another storage subsystem must not use the
additional field (the device must present a "nop" profile in
the kernel). Note that some devices must be reformatted at a
low level to support this option; for NVMe devices, see
nvme(1) id-ns LBA profiles.

No journal or bitmap is used in this mode. The device should
operate with native speed (without any overhead). This option
is available since the Linux kernel version 6.11.

--integrity-key-size bytes
The size of the data integrity key. Configurable only for HMAC
integrity. The default integrity key size is set to the same
as the hash output length.

--integrity-legacy-padding
Use inefficient legacy padding.

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

--integrity-no-wipe
Skip wiping of device authentication (integrity) tags. If you
skip this step, sectors will report an invalid integrity tag
until an application writes to the sector.

Skipping this step could also cause write failures due to IO
operation alignments. For example, kernel page cache can
request a read of a full page that fails due to an
uninitialized integrity tag. It is usually a bug in the
application that tries to read data that was not written
before.

--iter-time, -i <number of milliseconds>
The number of milliseconds to spend with PBKDF passphrase
processing. Specifying 0 as a parameter selects the
compiled-in default.

--key-description text
Set the key description in the keyring that will be used for
passphrase retrieval.

--key-file, -d file
Read the passphrase from the file.

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.

--keyfile-offset value
Skip value bytes at the beginning of the key file.

--keyfile-size, -l value
Read a maximum of value bytes from the key file. The default
is to read the whole file up to the compiled-in maximum that
can be queried with --help. Supplying more data than the
compiled-in maximum aborts the operation.

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

--key-size, -s bits
Sets key size in bits. The argument has to be a multiple of 8.
The possible key sizes are limited by the cipher and mode
used.

See /proc/crypto for more information. Note that the 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.

--key-slot, -S <0-N>
For LUKS operations that add key material, this option allows
you to specify which keyslot is selected for the new key.

The maximum number of keyslots depends on the LUKS version.
LUKS1 can have up to 8 keyslots. LUKS2 can have up to 32
keyslots based on keyslot area size and key size, but a valid
keyslot ID can always be between 0 and 31 for LUKS2.

--keyslot-cipher <cipher-spec>
This option can be used to set specific cipher encryption for
the LUKS2 keyslot area.

--keyslot-key-size <bits>
This option can be used to set a specific key size for the
LUKS2 keyslot area.

--label <label>, --subsystem <subsystem>
Set label and subsystem description for LUKS2 device. These
are similar to filesystem labels. The label and subsystem are
optional fields and can be later used in udev scripts to
trigger user actions once the device marked by these labels is
detected.

--luks2-keyslots-size size
This option can be used to set a specific size of the LUKS2
binary keyslot area (key material is encrypted there). The
value must be aligned to a multiple of 4096 bytes with a
maximum size 128MB. The <size> can be specified with a unit
suffix (for example, 128k).

--luks2-metadata-size size
This option can be used to enlarge the LUKS2 metadata (JSON)
area. The size includes 4096 bytes for binary metadata (usable
JSON area is smaller of the binary area). According to the
LUKS2 specification, only these values are valid: 16, 32, 64,
128, 256, 512, 1024, 2048 and 4096 kB. The <size> can be
specified with a unit suffix (for example, 128k).

--offset, -o <number of 512 byte sectors>
Start offset in the backend device in 512-byte sectors.

The --offset option sets the data offset (payload) of the data
device and must be aligned to 4096-byte sectors (must be a
multiple of 8). This option cannot be combined with
--align-payload option.

--pbkdf <PBKDF spec>
Set Password-Based Key Derivation Function (PBKDF) algorithm
for LUKS keyslot. The PBKDF can be: pbkdf2 (for PBKDF2
according to RFC2898), argon2i for Argon2i or argon2id for
Argon2id (see Argon2
<https://www.cryptolux.org/index.php/Argon2> for more info).

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 the cryptsetup --help output.

A PBKDF is used for increasing the dictionary and brute-force
attack cost for keyslot passwords. The parameters can be time,
memory and parallel cost.

For PBKDF2, only the 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 a particular LUKS2
keyslot with the cryptsetup-luksDump(8) command.

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 or cause out-of-memory conditions with
unconditional process termination. 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 the maximum is 4294967295 (maximum
for 32-bit unsigned integer). Memory and parallel costs are
not supported for PBKDF2. For Argon2i and Argon2id, the
minimum iteration count (CPU cost) is 4, and the maximum is
4294967295 (maximum for a 32-bit unsigned integer). Minimum
memory cost is 32 KiB and maximum is 4 GiB. If the memory cost
parameter is benchmarked (not specified by a parameter), it is
always in the range from 64 MiB to 1 GiB. Memory cost above
1GiB (up to the 4GiB maximum) can be setup only by the
--pbkdf-memory parameter. The parallel cost minimum is 1 and
maximum 4 (if enough CPU cores are available, otherwise it is
decreased by the available CPU cores).

WARNING: Increasing PBKDF computational costs above the
mentioned limits provides negligible additional security
improvement. While elevated costs significantly increase
brute-force overhead, they offer negligible protection against
dictionary attacks. The marginal cost increase for processing
an entire dictionary remains fundamentally insufficient.

The hardcoded PBKDF limits represent engineered trade-offs
between cryptographic security and operational usability. LUKS
maintains portability and must be used within a reasonable
time on resource-constrained systems.

Cryptsetup deliberately restricts maximum memory cost (4 GiB)
and parallel cost (4) parameters due to architectural
limitations (like embedded and legacy systems).

PBKDF memory cost mandates actual physical RAM allocation with
intensive write operations that must remain in physical RAM.
Any swap usage results in unacceptable performance
degradation. Memory management often overcommits allocations
beyond available physical memory, expecting most allocated
memory to remain unused. In such situations, as PBKDF always
uses all allocated memory, it frequently causes out-of-memory
failures that abort cryptsetup operations.

--pbkdf-force-iterations number
Avoid the PBKDF benchmark and set the time cost (iterations)
directly. It can be used only for a LUKS/LUKS2 device. See
--pbkdf option for more info.

--pbkdf-memory number
Set the memory cost for PBKDF (for Argon2i/id, the number
represents kilobytes). Note that it is the maximal value;
PBKDF benchmark or available physical memory can decrease it.
This option is not available for PBKDF2.

--pbkdf-parallel number
Set the parallel cost for PBKDF (number of threads, up to 4).
Note that it is the maximal value; it is decreased
automatically if the CPU online count is lower. This option is
not available for PBKDF2.

--progress-frequency seconds
Print a separate line every seconds with wipe progress.

--progress-json
Prints progress data in JSON format, which is suitable mostly
for machine processing. It prints a separate line every half
second (or based on --progress-frequency value). The JSON
output looks as follows during progress (except it’s a compact
single line):

{
"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 parser
limitations, all numbers are represented in a string format
due to the need for full 64-bit unsigned integers.

--sector-size bytes
Set encryption sector size for use with LUKS2 device type. It
must be a power of two and in the 512 - 4096 bytes range.

The encryption sector size is set based on the underlying data
device if not specified explicitly. For native 4096-byte
physical sector devices, it is set to 4096 bytes. For
4096/512e (4096-byte physical sector size with 512-byte sector
emulation), it is set to 4096 bytes. For drives reporting only
a 512-byte physical sector size, it is set to 512 bytes. If
the data device is a regular file (container), it is set to
4096 bytes.

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

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

Note that using a sector size larger than the underlying
storage device’s physical sector size may result in data
corruption during unexpected power failures. A power failure
during write operations may result in only partial completion
of the encryption sector write, leaving encrypted data in an
inconsistent state that cannot be properly decrypted.

--timeout, -t seconds
The number of seconds to wait before a timeout on passphrase
input via terminal. It is relevant every time a passphrase is
asked. It has no effect if used in conjunction with
--key-file.

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.

--type type
Specifies required device type, for more info, read the BASIC
ACTIONS section in cryptsetup(8).

--usage
Show short option help.

--use-random, --use-urandom
For luksFormat, these options define which kernel random
number generator will be used to create the volume key (which
is a long-term key).

Do not use these options with recent kernels (later than
version 5.6). For more details, see NOTES ON RANDOM NUMBER
GENERATORS in cryptsetup(8) and urandom(4).

--uuid UUID
Use the provided UUID for the luksFormat command instead of
generating a new one. Changes the existing UUID when used with
the luksUUID command.

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

--verify-passphrase, -y
When interactively asking for a passphrase, ask for it twice
and complain if both inputs do not match. Ignored on input
from file or stdin.

--version, -V
Show the program version.

--volume-key-file file, --master-key-file file (OBSOLETE alias)
Use a volume key stored in a file.

WARNING: If you create your own volume key, you need to make
sure to do it right. Otherwise, you can end up with a
low-entropy or otherwise partially predictable volume key,
which will compromise security.

REPORTING BUGS top

       Report bugs at cryptsetup mailing list
       <[email protected]> or in Issues project section
       <https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.

       Please attach the output of the failed command with --debug option
       added.

CRYPTSETUP top

       Part of cryptsetup project
       <https://gitlab.com/cryptsetup/cryptsetup/>. This page is part of
       the Cryptsetup ((open-source disk encryption)) project.
       Information about the project can be found at 
       ⟨https://gitlab.com/cryptsetup/cryptsetup⟩. If you have a bug
       report for this manual page, send it to [email protected]. This
       page was obtained from the project's upstream Git repository
       ⟨https://gitlab.com/cryptsetup/cryptsetup.git⟩ on 2025-08-11. (At
       that time, the date of the most recent commit that was found in
       the repository was 2025-08-01.) If you discover any rendering
       problems in this HTML version of the page, or you believe there is
       a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       [email protected]

cryptsetup 2.8.1-git            2025-08-09       CRYPTSETUP-LUKSFORMAT(8)

Pages that refer to this page: cryptsetup(8), cryptsetup-reencrypt(8)