cryptsetup-luksAddKey(8) — Linux manual page

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

CRYPTSETUP-LUKSADDKEY(8)   Maintenance Commands  CRYPTSETUP-LUKSADDKEY(8)

NAME         top

       cryptsetup-luksAddKey - add a new passphrase

SYNOPSIS         top

       cryptsetup luksAddKey [<options>] <device> [<key file with new
       key>]

DESCRIPTION         top

       Adds a keyslot protected by a new passphrase. An existing
       passphrase must be supplied interactively, via --key-file or LUKS2
       token (plugin). Alternatively to the existing passphrase, the user
       may pass directly the volume key (via --volume-key-file or
       --volume-key-keyring). The new passphrase to be added can be
       specified interactively, read from the file given as the
       positional argument (also via --new-keyfile parameter) or via
       LUKS2 token.

       The --unbound option creates a new unbound LUKS2 keyslot. An
       unbound keyslot stores an independent key that cannot be used for
       device activation. A new random key is generated if you don’t pass
       a new key via the --volume-key-file option. The existing
       passphrase for any active keyslot is not required.

       Some parameters are effective only if used with the LUKS2 format
       that supports per-keyslot parameters. For LUKS1, the PBKDF type
       and hash algorithm are always the same for all keyslots.

       <options> can be [--key-file, --keyfile-offset, --keyfile-size,
       --new-keyfile, --new-keyfile-offset, --new-keyfile-size,
       --key-slot, --new-key-slot, --volume-key-file,
       --volume-key-keyring, --force-password, --hash, --header,
       --disable-locks, --iter-time, --pbkdf, --pbkdf-force-iterations,
       --pbkdf-memory, --pbkdf-parallel, --unbound, --type,
       --keyslot-cipher, --keyslot-key-size, --key-size, --timeout,
       --token-id, --token-type, --token-only, --new-token-id,
       --verify-passphrase, --external-tokens-path].

OPTIONS         top

       --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.

       --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).

       --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).

       --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>
           The specified hash is used for PBKDF2 and the AF splitter.

       --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.

           For commands that change the LUKS header (e.g., luksAddKey),
           specify the device or file with the LUKS header directly as
           the LUKS device.

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

       --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.

           The passphrase supplied via --key-file is always the
           passphrase for the existing keyslot requested by the command.

           If you want to set a new passphrase via key file, you have to
           use a positional argument or parameter --new-keyfile.

           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
           Provide volume key size in bits. The argument has to be a
           multiple of 8.

           This option is required when the parameter --volume-key-file
           is used to provide current volume key. Also, it is used when a
           new unbound keyslot is created by specifying --unbound
           parameter.

       --key-slot, -S <0-N>
           When used together with the parameter --new-key-slot, this
           option allows you to specify which keyslot is selected for
           unlocking the volume key.

           This option is ignored if the existing volume key gets
           unlocked via LUKS2 token (--token-id, --token-type or
           --token-only parameters) or when volume key is provided
           directly via --volume-key-file parameter.

           To maintain backward compatibility, without --new-key-slot
           parameter, 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.

       --new-keyfile name
           Read the passphrase for a new keyslot from a file.

           If the name given is "-", then the passphrase will be read
           from stdin. In this case, reading will not stop at newline
           characters.

           This is an alternative method to positional argument when
           adding a new passphrase via keyfile.

       --new-keyfile-offset value
           Skip value bytes at the start when adding a new passphrase
           from the key file.

       --new-keyfile-size value
           Read a maximum of value bytes when adding a new passphrase
           from the key file. The default is to read the whole file up to
           the compiled-in maximum length that can be queried with
           --help. Supplying more than the compiled-in maximum aborts the
           operation. When --new-keyfile-offset is also given, reading
           starts after the offset.

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

       --new-key-slot <0-N>
           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.

       --new-token-id <id>
           Specify what token to use to get the passphrase for a new
           keyslot.

       --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.

       --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 when unlocking the existing keyslot
           to get the volume key.

       --token-only
           Use only LUKS2 tokens to unlock the existing volume key.

           To create a new keyslot using the passphrase provided by a
           token, use --new-token-id parameter.

       --token-type type
           Specify what token type (all type tokens) to use when
           unlocking the existing keyslot to get the volume key.

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

       --unbound
           Creates a new LUKS2 unbound keyslot.

       --usage
           Show short option help.

       --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.

           This allows adding a new keyslot without having to know the
           passphrase to the existing one. It may also be used when no
           keyslot is active.

           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.

       --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).

EXAMPLES         top

       The interactive passphrase prompt is always the default method
       when not specified otherwise.

       Add new keyslot using interactive passphrase prompt for both
       existing and new passphrases:

       cryptsetup luksAddKey /dev/device

       Add a new keyslot using LUKS2 tokens to unlock the existing
       keyslot with an interactive passphrase prompt for the new
       passphrase:

       cryptsetup luksAddKey --token-only /dev/device

       Add new keyslot using LUKS2 systemd-tpm2 tokens to unlock existing
       keyslot with interactive passphrase prompt for new passphrase
       (systemd-tpm2 token plugin must be available):

       cryptsetup luksAddKey --token-type systemd-tpm2 /dev/device

       Add new keyslot using interactive passphrase prompt for existing
       keyslot, reading new passphrase from key_file:

       cryptsetup luksAddKey --new-keyfile key_file /dev/device or
       cryptsetup luksAddKey /dev/device key_file

       Add new keyslot using volume stored in volume_key_file and LUKS2
       token in slot 5 to get new keyslot passphrase (token in slot 5
       must exist and respective token plugin must be available):

       cryptsetup luksAddKey --volume-key-file volume_key_file
       --new-token-id 5 /dev/device

REPORTING BUGS         top

       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         top

       Cryptsetup FAQ
       <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>

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

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 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
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       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-LUKSADDKEY(8)

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