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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REPORTING BUGS | SEE ALSO | CRYPTSETUP |
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CRYPTSETUP-LUKSFORMAT(8) Maintenance Commands CRYPTSETUP-LUKSFORMAT(8)
cryptsetup-luksFormat - initialize a LUKS partition and set the
initial passphrase
cryptsetup luksFormat [<options>] <device> [<key file>]
Initializes a LUKS partition and sets the initial passphrase (for
key-slot 0), either via prompting or via <key file>. Note that if
the second argument is present, then the passphrase is taken from
the file given there, without the need to use the --key-file
option. Also note that for both forms of reading the passphrase
from a file you can give '-' as 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., mounted filesystem, used in LVM, active
RAID member, etc. The device or filesystem has to be un-mounted
in order to call luksFormat.
To use specific version of LUKS format, use --type luks1 or type
luks2.
<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].
WARNING: Doing a luksFormat on an existing LUKS container will
make all data in the old container permanently irretrievable
unless you have a header backup.
--type <device-type>
Specifies required device type, for more info read BASIC
ACTIONS section in cryptsetup(8).
--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
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.
--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.
--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.
--key-file, -d name
Read the passphrase from 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.
--volume-key-file, --master-key-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.
--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).
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.
--key-slot, -S <0-N>
For LUKS operations that add key material, this option allows
you to specify which key slot is selected for the new key.
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.
--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 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.
--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 data
device and must be aligned to 4096-byte sectors (must be
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 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).
--iter-time, -i <number of milliseconds>
The number of milliseconds to spend with PBKDF passphrase
processing. Specifying 0 as parameter selects the compiled-in
default.
--pbkdf-memory <number>
Set the memory cost for PBKDF (for Argon2i/id the number
represents kilobytes). Note that it is 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 maximal value, it is decreased automatically
if CPU online count is lower. This option is not available
for PBKDF2.
--pbkdf-force-iterations <num>
Avoid PBKDF benchmark and set time cost (iterations)
directly. It can be used for LUKS/LUKS2 device only. See
--pbkdf option for more info.
--progress-frequency seconds
Print separate line every seconds with wipe progress.
--progress-json
Prints progress data in JSON format suitable mostly for
machine processing. It prints separate line every half second
(or based on --progress-frequency value). The JSON output
looks as follows during progress (except it’s 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 parsers
limitations all numbers are represented in a string format
due to need of full 64bit unsigned integers.
--timeout, -t <number of seconds>
The number of seconds to wait before 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.
--align-payload <number of 512 byte sectors>
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.
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.
--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.
--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
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 ciphertext device and can be zero.
--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).
--disable-locks
Disable lock protection for metadata on disk. This option is
valid only for LUKS2 and 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).
--disable-keyring
Do not load volume key in kernel keyring and store it
directly in the dm-crypt target instead. This option is
supported only for the LUKS2 type.
--sector-size bytes
Set sector size for use with disk encryption. It must be
power of two and in range 512 - 4096 bytes. This option is
available only with LUKS2 format.
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.
--label <LABEL> --subsystem <SUBSYSTEM>
Set label and subsystem description for LUKS2 device. The
label and subsystem are optional fields and can be later used
in udev scripts for triggering user actions once the device
marked by these labels is detected.
--integrity <integrity algorithm>
Specify integrity algorithm to be used for authenticated disk
encryption in LUKS2.
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).
--integrity-legacy-padding
Use inefficient legacy padding.
WARNING: Do not use this option until you need compatibility
with specific old kernel.
--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 LUKS2 specification, only these values are valid: 16, 32,
64, 128, 256, 512, 1024, 2048 and 4096 kB The <size> can be
specified with unit suffix (for example 128k).
--luks2-keyslots-size <size>
This option can be used to set specific size of the LUKS2
binary keyslot area (key material is encrypted there). The
value must be aligned to multiple of 4096 bytes with maximum
size 128MB. The <size> can be specified with unit suffix (for
example 128k).
--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 specific key size for the
LUKS2 keyslot area.
--integrity-no-wipe
Skip wiping of device authentication (integrity) tags. If you
skip this step, sectors will report invalid integrity tag
until an application write to the sector.
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.
--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.
--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.
--version, -V
Show the program version.
--usage
Show short option help.
--help, -?
Show help text and default parameters.
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.
Cryptsetup FAQ
<https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>
cryptsetup(8), integritysetup(8) and veritysetup(8)
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 dm-crypt@saout.de. This
page was obtained from the project's upstream Git repository
⟨https://gitlab.com/cryptsetup/cryptsetup.git⟩ on 2023-12-22. (At
that time, the date of the most recent commit that was found in
the repository was 2023-12-20.) 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
man-pages@man7.org
cryptsetup 2.6.1-git 2022-12-14 CRYPTSETUP-LUKSFORMAT(8)
Pages that refer to this page: cryptsetup(8), cryptsetup-reencrypt(8)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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