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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REPORTING BUGS | SEE ALSO | CRYPTSETUP |
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CRYPTSETUP-OPEN(8) Maintenance Commands CRYPTSETUP-OPEN(8)
cryptsetup-open, cryptsetup-create, cryptsetup-plainOpen,
cryptsetup-luksOpen, cryptsetup-loopaesOpen, cryptsetup-
tcryptOpen, cryptsetup-bitlkOpen, cryptsetup-fvault2Open - open an
encrypted device and create a mapping with a specified name
cryptsetup open --type <device_type> [<options>] <device> <name>
Opens (creates a mapping with) <name> backed by device <device>.
Device type can be plain, luks (default), luks1, luks2, loopaes or
tcrypt.
For backward compatibility, there are open command aliases:
create (argument-order <name> <device>): open --type plain
plainOpen: open --type plain
luksOpen: open --type luks
loopaesOpen: open --type loopaes
tcryptOpen: open --type tcrypt
bitlkOpen: open --type bitlk
<options> are type-specific and are described below for individual
device types. For create, the order of the <name> and <device>
options is inverted for historical reasons; all other aliases use
the standard <device> <name> order.
PLAIN
open --type plain <device> <name> --cipher <spec> --key-size
<bits> --hash <alg>
plainOpen <device> <name> (old syntax)
create <name> <device> (OBSOLETE syntax)
Opens (creates a mapping with) <name> backed by device <device>.
You should always specify options --cipher, --key-size and (if no
keyfile or keyring is used) then also --hash to avoid
incompatibility, as default values can differ in older cryptsetup
versions.
The plain format also allows retrieving a volume key from a kernel
keyring specified by --volume-key-keyring. The key in the kernel
keyring must be configured before issuing cryptsetup commands, as
cryptsetup does not upload any keys to the keyring in plain mode.
For subsequent commands (like resize), the user must ensure that
the key in the keyring is unchanged. Otherwise, reloading the key
can cause data corruption after an unexpected key change.
<options> can be [--hash, --cipher, --sector-size, --key-file,
--keyfile-size, --keyfile-offset, --key-size, --offset, --skip,
--device-size, --size, --readonly, --shared, --allow-discards,
--refresh, --timeout, --verify-passphrase, --iv-large-sectors,
--volume-key-keyring].
EXAMPLES:
To map the encrypted device /dev/sda10 to the decrypted device
/dev/mapper/e1, you can use:
cryptsetup open --type plain --cipher aes-cbc-essiv:sha256
--key-size 256 --hash sha256 /dev/sda10 e1
The decrypted device can then be used as a normal block device to
mount a filesystem.
To map a device with a volume key in the preconfigured trusted or
encrypted keyring, you need to specify the keyring with the key
and remove the hash specification, for example, to use
%trusted:mykey:
cryptsetup open --type plain /dev/sda10 e1
--volume-key-keyring=%trusted:mykey --cipher aes-xts-plain64
--key-size 256
Note that the key size must match the preconfigured key in the
keyring.
LUKS
open <device> <name>
open --type <luks1|luks2> <device> <name> (explicit version
request)
luksOpen <device> <name> (old syntax)
Opens the LUKS device <device> and sets up a mapping <name> after
successful verification of the supplied passphrase.
First, the passphrase is searched in LUKS2 tokens unprotected by
PIN. If such a token does not exist (or fails to unlock keyslot)
and the passphrase is not supplied via --key-file, the command
prompts for passphrase interactively.
If there is a valid LUKS2 token but it requires a PIN to unlock
the assigned keyslot, it is not used unless one of the following
options is added: --token-only, --token-type where type matches
the desired PIN-protected token or --token-id with id matching the
PIN-protected token.
<options> can be [--key-file, --keyfile-offset, --keyfile-size,
--readonly, --test-passphrase, --allow-discards, --header,
--key-slot, --volume-key-file, --token-id, --token-only,
--token-type, --disable-external-tokens, --disable-keyring,
--disable-locks, --type, --refresh, --serialize-memory-hard-pbkdf,
--unbound, --tries, --timeout, --verify-passphrase, --persistent,
--volume-key-keyring, --link-vk-to-keyring,
--external-tokens-path].
loopAES
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>.
If the key file is encrypted with GnuPG, then you have to use
--key-file=- and decrypt it before use, e.g., like this: gpg
--decrypt <keyfile> | cryptsetup loopaesOpen --key-file=- <device>
<name>.
The loop-AES extension cannot use the direct input of the key file
on the real terminal because the keys are separated by
end-of-line, and only part of the multi-key file would be read. If
you need it in script, just use the pipe redirection: echo
$keyfile | cryptsetup loopaesOpen --key-file=- <device> <name>.
Use --keyfile-size to specify the proper key length if needed.
Use --offset to specify device offset. Note that the units need to
be specified in terms of 512-byte sectors.
Use --skip to specify the IV offset. If the original device used
an offset but did not use it in IV sector calculations, you must
explicitly use --skip 0 in addition to the offset parameter.
Use --hash to override the default hash function for passphrase
hashing (otherwise it is detected according to key size).
<options> can be [--cipher, --key-file, --keyfile-size,
--keyfile-offset, --key-size, --offset, --skip, --hash,
--readonly, --allow-discards, --refresh].
TrueCrypt and VeraCrypt
open --type tcrypt <device> <name>
tcryptOpen <device> <name> (old syntax)
Opens the TCRYPT (TrueCrypt and VeraCrypt compatible) <device> and
sets up a mapping <name>.
The --key-file option allows a combination of file content with
the passphrase The --key-file option can be repeated. Note that
using keyfiles differs from LUKS keyfile logic.
If --cipher or --hash options are used, only cipher chains or
PBKDF2 variants with the specified hash algorithms are checked.
This could speed up unlocking the device (but also reveals some
information about the container).
If you use --header in combination with hidden or system options,
the header file must contain specific headers in the same
positions as the original encrypted container.
Option --allow-discards cannot be combined with option
--tcrypt-hidden. For normal mapping, it can cause the destruction
of hidden volume (hidden volume appears as unused space for outer
volume, so this space can be discarded).
<options> can be [--key-file, --tcrypt-hidden, --tcrypt-system,
--tcrypt-backup, --readonly, --test-passphrase, --allow-discards,
--veracrypt (ignored), --disable-veracrypt, --veracrypt-pim,
--veracrypt-query-pim, --header, --cipher, --hash, --tries,
--timeout, --verify-passphrase].
BitLocker
open --type bitlk <device> <name>
bitlkOpen <device> <name> (old syntax)
Opens the BITLK (a BitLocker compatible) <device> and sets up a
mapping <name>.
Note that --test-passphrase doesn’t work with --volume-key-file
because we cannot check whether the provided volume key is correct
for this device. When using --volume-key-file, the device will be
opened even if the provided key is incorrect.
<options> can be [--key-file, --keyfile-offset, --keyfile-size,
--key-size, --readonly, --test-passphrase, --allow-discards
--volume-key-file, --tries, --timeout, --verify-passphrase].
FileVault2
open --type fvault2 <device> <name>
fvault2Open <device> <name> (old syntax)
Opens the FVAULT2 (a FileVault2 compatible) <device> and sets up a
mapping <name>.
<options> can be [--key-file, --keyfile-offset, --keyfile-size,
--key-size, --readonly, --test-passphrase, --allow-discards
--volume-key-file, --tries, --timeout, --verify-passphrase].
--allow-discards
Allow the use of discard (TRIM) requests for the device. This
is also not supported for LUKS2 devices with data integrity
protection.
WARNING: This command can have a negative security impact
because it can make filesystem-level operations visible on the
physical device. For example, information leaking filesystem
type, used space, etc., may be extractable from the physical
device if the discarded blocks can be located later. If in
doubt, do not use it.
A kernel version of 3.1 or later is needed. For earlier
kernels, this option is ignored.
--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 for the plain device type.
For the tcrypt device type, it restricts checked cipher chains
when looking for the header.
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.
--device-size size[units]
Instead of the real device size, use the specified value.
Usable only with plain device type.
If no unit suffix is specified, the size is in bytes.
Unit suffix can be S for 512 byte sectors, K/M/G/T (or KiB,
MiB, GiB, TiB) for units with 1024 base or KB/MB/GB/TB for
1000 base (SI scale).
--disable-external-tokens
Disable loading of plugins for external LUKS2 tokens.
--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).
--disable-veracrypt
This option can be used to disable VeraCrypt compatible mode
(only TrueCrypt devices are recognized). See the TCRYPT
section in cryptsetup(8) for more info.
--external-tokens-path <absolute path>
Override the system directory path where cryptsetup searches
for external token handlers (or token plugins). It must be an
absolute path (starting with '/' character).
--hash, -h <hash-spec>
Specifies the passphrase hash. Applies to plain and loopaes
device types only.
For the tcrypt device type, it restricts the checked PBKDF2
variants when looking for the header.
--header <device or file storing the LUKS header>
Specify a detached (separated) metadata device or file where
the header is stored.
WARNING: There is no check whether the ciphertext device
specified actually belongs to the header given. In fact, you
can specify an arbitrary device as the ciphertext device with
the --header option. Use with care.
--help, -?
Show help text and default parameters.
--iv-large-sectors
Count Initialization Vector (IV) in larger sector size (if
set) instead of 512-byte sectors. This option can be used only
with the plain device type.
This option does not have any performance or security impact;
use it only for accessing incompatible existing disk images
from other systems that require this option.
--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.
With plain device type, the passphrase obtained via --key-file
option is passed directly in dm-crypt. Unlike the interactive
mode (stdin), where the digest of the passphrase is passed in
dm-crypt instead.
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 plain and luks devices. For LUKS2
devices in reencryption, you may use the parameter twice to
specify both old and new volume key sizes. Each --key-size
option corresponds to the respective --volume-key-file
parameter (also allowed to be used up to two times).
--key-slot, -S <0-N>
This option selects a specific keyslot to compare the
passphrase against. If the given passphrase would only matches
a different keyslot, the operation fails.
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.
--link-vk-to-keyring <keyring description>::<key description>
Link the volume key in a keyring with the specified key name.
The volume key is linked only if the requested action is
successfully finished (with --test-passphrase, the verified
volume key is linked in a keyring without taking further
action).
The <keyring description> string has to contain the existing
kernel keyring description. The keyring name may be optionally
prefixed with "%:" or "%keyring:" type descriptions. Or, the
keyring may also be specified directly by numeric key id.
Also, special keyring notations starting with "@" may be used
to select existing predefined kernel keyrings.
The string "::" is a delimiter used to separate the keyring
description and key description.
<key description> part describes key type and key name of
volume key linked in the keyring described in <keyring
description>. The type may be specified by adding a
"%<type_name>:" prefix in front of the key name. If the type
is missing, the default user type is applied. If the key of
the same name and type already exists (already linked in the
keyring), it will get replaced in the process.
See also the KEY IDENTIFIERS section of keyctl(1).
--offset, -o <number of 512 byte sectors>
Start offset in the backend device in 512-byte sectors. This
option is only relevant with plain or loopaes device types.
--perf-high_priority
Set dm-crypt workqueues and the writer thread to high
priority. This improves throughput and latency of dm-crypt
while degrading the general responsiveness of the system.
This option is available only for low-level dm-crypt
performance tuning, use only if you need a change to the
default dm-crypt behaviour. Needs kernel 6.10 or later.
--perf-no_read_workqueue, --perf-no_write_workqueue
Bypass dm-crypt internal workqueue and process read or write
requests synchronously.
These options are available only for low-level dm-crypt
performance tuning, use only if you need a change to the
default dm-crypt behaviour. Needs kernel 5.9 or later.
--perf-same_cpu_crypt
Perform encryption using the same CPU on which that IO was
submitted. The default is to use an unbound workqueue so that
encryption work is automatically balanced between available
CPUs.
This option is available only for low-level dm-crypt
performance tuning, use only if you need a change to the
default dm-crypt behaviour.
--perf-submit_from_crypt_cpus
Disable offloading writes to a separate thread after
encryption. There are some situations where offloading write
bios from the encryption threads to a single thread degrades
performance significantly. The default is to offload write
bios to the same thread.
This option is available only for low-level dm-crypt
performance tuning, use only if you need a change to the
default dm-crypt behaviour.
--persistent
If used with LUKS2 devices and activation commands like open
or refresh, the specified activation flags are persistently
written into metadata and used next time automatically, even
for normal activation. (No need to use cryptab or other system
configuration files.)
If you need to remove a persistent flag, use --persistent
without the flag you want to remove (e.g., to disable the
persistently stored discard flag, use --persistent without
--allow-discards).
Only --allow-discards, --perf-same_cpu_crypt,
--perf-submit_from_crypt_cpus, --perf-no_read_workqueue,
--perf-no_write_workqueue and --integrity-no-journal can be
stored persistently.
--readonly, -r
Set up a read-only mapping.
--refresh
Refreshes an active device with a new set of parameters. See
cryptsetup-refresh(8) for more details.
--sector-size bytes
Set encryption sector size for use with plain device type. It
must be a power of two and in the 512 - 4096 bytes range. The
default encryption sector size is 512 bytes.
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.
--serialize-memory-hard-pbkdf
Use a global lock to serialize unlocking of keyslots using
memory-hard PBKDF.
This is a workaround for a specific situation when multiple
devices are activated in parallel, and the system, instead of
reporting out of memory, starts unconditionally stop processes
using the out-of-memory killer.
DO NOT USE this switch until you are implementing the boot
environment with parallel devices activation!
--shared
Creates an additional mapping for one common ciphertext
device. Arbitrary mappings are supported. This option is only
relevant for the plain device type. Use --offset, --size and
--skip to specify the mapped area.
--size, -b <number of 512 byte sectors>
Set the size of the device in sectors of 512 bytes. Usable
only with plain device type.
--skip, -p <number of 512 byte sectors>
Start offset used in IV calculation in 512-byte sectors (how
many sectors of the encrypted data to skip at the beginning).
This option is only relevant with plain or loopaes device
types.
Hence, if --offset n, and --skip s, sector n (the first sector
of the encrypted device) will get a sector number of s for the
IV calculation.
--tcrypt-backup, --tcrypt-hidden, --tcrypt-system
Specify which TrueCrypt on-disk header will be used to open
the device. See the TCRYPT section in cryptsetup(8) for more
info.
Using a system-encrypted device with the --tcrypt-system
option requires specific settings to work as expected.
TrueCrypt/VeraCrypt supports full system encryption (only a
partition table is not encrypted) or system partition
encryption (only a system partition is encrypted). The
metadata header then contains the offset and size of the
encrypted area. Cryptsetup needs to know the specific
partition offset to calculate encryption parameters. To
properly map a partition, you must specify a real partition
device so cryptsetup can calculate this offset.
While you can use a full device as a parameter (/dev/sdb),
always prefer to specify the partition you want to map
(/dev/sdb1), as only the system partition mode can be detected
this way.
For mapping images (stored in a file), you can use the
additional --header option with the real partition device. If
the --header is used (and it is different from the data
image), cryptsetup expects that the data image contains a
snapshot of the data partition only.
If --header is not used (or points to the same image),
cryptsetup expects that the image contains a full disk
(including the partition table). This can map a full encrypted
area that is not directly mountable as a filesystem. Please
prefer creating a loop device with partitions (losetup -P, see
losetup(8) man page) and use a real partition (/dev/loopXp1)
as the device parameter.
--test-passphrase
Do not activate the device, just verify the passphrase. The
device mapping name is not mandatory if this option is used.
--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.
--token-id
Specify what token to use and allow the token PIN prompt to
take precedence over the interactive keyslot passphrase
prompt. If omitted, all available tokens (not protected by
PIN) will be checked before proceeding further with the
passphrase prompt.
--token-only
Do not proceed further with the action if the token-based
keyslot unlock failed. Without the option, the action asks for
a passphrase to proceed further.
It allows LUKS2 tokens protected by PIN to take precedence
over the interactive keyslot passphrase prompt.
--token-type type
Restrict tokens eligible for operation to a specific token
type. Mostly useful when no --token-id is specified.
It allows LUKS2 type tokens protected by PIN to take
precedence over the interactive keyslot passphrase prompt.
--tries, -T
How often the input of the passphrase shall be retried. The
default is 3 tries.
--type type
Specifies required device type, for more info, read the BASIC
ACTIONS section in cryptsetup(8).
--unbound
Allowed only together with --test-passphrase parameter, it
allows one to test the passphrase for an unbound LUKS2
keyslot. Otherwise, an unbound keyslot passphrase can be
tested only when a specific keyslot is selected via --key-slot
parameter.
--usage
Show short option help.
--veracrypt
This option is ignored as VeraCrypt compatible mode is
supported by default.
--veracrypt-pim, --veracrypt-query-pim
Use a custom Personal Iteration Multiplier (PIM) for the
VeraCrypt device. See the TCRYPT section in cryptsetup(8) for
more info.
--verify-passphrase, -y
When interactively asking for a passphrase, ask for it twice
and complain if both inputs do not match. Advised when
creating a plain type mapping for the first time. 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.
This allows one to open luks and bitlk device types without
giving a passphrase.
For devices in reencryption, the option may be used twice to
specify both old and new volume keys. When using the option
twice, make sure you pair each --volume-key-file option with
the respective --key-size parameter as well.
--volume-key-keyring <key description>
Use a volume key stored in a keyring. This allows one to open
luks and plain device types without giving a passphrase.
For LUKS, the key and associated type have to be readable from
userspace so that the volume key digest may be verified before
activation. For devices in reencryption, the option may be
used twice to specify both old and new volume keys.
For PLAIN type, the user must ensure that the key in the
keyring is unchanged since activation. Otherwise, reloading
the key can cause data corruption after an unexpected key
change.
The <key description> uses keyctl-compatible syntax. This can
either be a numeric key ID or a string name in the format
%<key type>:<key name>. See also the KEY IDENTIFIERS section
of keyctl(1). When no %<key type>: prefix is specified, we
assume the key type is user (default type).
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.
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 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
man-pages@man7.org
cryptsetup 2.8.1-git 2025-08-09 CRYPTSETUP-OPEN(8)
Pages that refer to this page: cryptsetup(8)
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