cryptsetup-open - Man Page

• Open a Luks volume and create a decrypted mapping at /dev/mapper/mapping_name: cryptsetup open /dev/sdXY mapping_name
• Use a keyfile instead of a passphrase: cryptsetup open --key-file path/to/file /dev/sdXY mapping_name
• Allow the use of TRIM on the device: cryptsetup open --allow-discards /dev/sdXY mapping_name
• Write the --allow-discards option into the Luks header (the option will then always be used when you open the device): cryptsetup open --allow-discards --persistent /dev/sdXY mapping_name
• Open a Luks volume and make the decrypted mapping read-only: cryptsetup open --readonly /dev/sdXY mapping_name

tldr.sh

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.

--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 plain device type.

For tcrypt device type it restricts checked cipher chains when looking for 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 real device size, use 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 volume key in kernel keyring and 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 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). Only for TCRYPT extension. See TCRYPT section in cryptsetup(8) for more info.

--external-tokens-path absolute_path

Override system directory path where cryptsetup searches for external token handlers (or token plugins). It must be absolute path (starting with '/' character).

--hash,  -h <hash-spec>

Specifies the passphrase hash. Applies to plain and loopaes device types only.

For tcrypt device type, it restricts checked PBKDF2 variants when looking for header.

--header <device or file storing the LUKS header>

Specify 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 bytes sectors. This option can be used only with plain device type.

NOTE: 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-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.

NOTE: With plain device type, the passphrase obtained via --key-file option is passed directly in dm-crypt. Unlike the interactive mode (stdin) where digest (--hash option) 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 key-size in /proc/crypto is stated in bytes.

This option can be used for plain device type only.

--key-slot,  -S <0-N>

This option selects a specific key-slot to compare the passphrase against. If the given passphrase would only match a different key-slot, the operation fails.

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.

--link-vk-to-keyring <keyring_description>::<key_description>

Link volume key in a keyring with specified key name. The volume key is linked only if requested action is successfully finished (with --test-passphrase the verified volume key is linked in a keyring without taking further action).

<keyring_description> string has to contain 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 delimiter used to separate 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 "%<type_name>:" prefix in front of key name. If type is missing default user type is applied. If the key of same name and same type already exists (already linked in the keyring) it will get replaced in the process.

See also 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-no_read_workqueue,  --perf-no_write_workqueue

Bypass dm-crypt internal workqueue and process read or write requests synchronously.

NOTE: These options are available only for low-level dm-crypt performance tuning, use only if you need a change to default dm-crypt behaviour. Needs kernel 5.9 or later.

--perf-same_cpu_crypt

Perform encryption using the same cpu that IO was submitted on. The default is to use an unbound workqueue so that encryption work is automatically balanced between available CPUs.

NOTE: This option is available only for low-level dm-crypt performance tuning, use only if you need a change to default dm-crypt behaviour. Needs kernel 4.0 or later.

--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.

NOTE: This option is available only for low-level dm-crypt performance tuning, use only if you need a change to default dm-crypt behaviour. Needs kernel 4.0 or later.

--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 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 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 power of two and in range 512 - 4096 bytes. The default mode is 512 bytes.

Note that if sector size is higher than underlying device hardware sector, using this option can increase risk on incomplete sector writes during a power fail.

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.

--serialize-memory-hard-pbkdf

Use a global lock to serialize unlocking of keyslots using memory-hard PBKDF.

NOTE: This is (ugly) workaround for a specific situation when multiple devices are activated in parallel and system instead of reporting out of memory starts unconditionally stop processes using out-of-memory killer.

DO NOT USE this switch until you are implementing 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 TCRYPT section in cryptsetup(8) for more info.

--test-passphrase

Do not activate the device, just verify passphrase. The device mapping name is not mandatory if this option is used.

--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.

--token-id

Specify what token to use and allow token PIN prompt to take precedence over interactive keyslot passphrase prompt. If omitted, all available tokens (not protected by PIN) will be checked before proceeding further with passphrase prompt.

--token-only

Do not proceed further with action if token based keyslot unlock failed. Without the option, action asks for passphrase to proceed further.

It allows LUKS2 tokens protected by PIN to take precedence over interactive keyslot passphrase prompt.

--token-type type

Restrict tokens eligible for operation to specific token type. Mostly useful when no --token-id is specified.

It allows LUKS2 type tokens protected by PIN to take precedence over interactive keyslot passphrase prompt.

--tries,  -T

How often the input of the passphrase shall be retried. The default is 3 tries.

--type <device-type>

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

--unbound

Allowed only together with --test-passphrase parameter, it allows one to test passphrase for unbound LUKS2 keyslot. Otherwise, unbound keyslot passphrase can be tested only when 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 VeraCrypt device. See 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,  --master-key-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.

--volume-key-keyring <key description>

Use a volume key stored in a keyring. This allows one to open luks and device types without giving a passphrase. The key and associated type has to be readable from userspace so that volume key digest may be verified in before activation.

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 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 or in Issues project section.

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

Cryptsetup FAQ

cryptsetup(8), integritysetup(8) and veritysetup(8)

Part of cryptsetup project.

cryptsetup(8).

The man pages cryptsetup-bitlkOpen(8), cryptsetup-create(8), cryptsetup-fvault2Open(8), cryptsetup-loopaesOpen(8), cryptsetup-luksOpen(8), cryptsetup-plainOpen(8) and cryptsetup-tcryptOpen(8) are aliases of cryptsetup-open(8).