cryptsetup-luksChangeKey(8) — Linux manual page



NAME         top

       cryptsetup-luksChangeKey - change an existing passphrase

SYNOPSIS         top

       cryptsetup luksChangeKey [<options>] <device> [<new key file>]

DESCRIPTION         top

       Changes an existing passphrase. The passphrase to be changed must
       be supplied interactively or via --key-file. The new passphrase
       can be supplied interactively or in a file given as the
       positional argument.

       If a key-slot is specified (via --key-slot), the passphrase for
       that key-slot must be given and the new passphrase will overwrite
       the specified key-slot. If no key-slot is specified and there is
       still a free key-slot, then the new passphrase will be put into a
       free key-slot before the key-slot containing the old passphrase
       is purged. If there is no free key-slot, then the key-slot with
       the old passphrase is overwritten directly.

       WARNING: If a key-slot is overwritten, a media failure during
       this operation can cause the overwrite to fail after the old
       passphrase has been wiped and make the LUKS container

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

       <options> can be [--key-file, --keyfile-offset, --keyfile-size,
       --new-keyfile-offset, --iter-time, --pbkdf,
       --pbkdf-force-iterations, --pbkdf-memory, --pbkdf-parallel,
       --new-keyfile-size, --key-slot, --force-password, --hash,
       --header, --disable-locks, --type, --keyslot-cipher,
       --keyslot-key-size, --timeout, --verify-passphrase].

OPTIONS         top

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

       --hash, -h <hash-spec>
           The specified hash is used for PBKDF2 and AF splitter.

       --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

           The passphrase supplied via --key-file is always the
           passphrase for 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.

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

       --new-keyfile-size value
           Read a maximum of value bytes when adding a new passphrase
           from 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.

       --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.

       --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
           <> 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

           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

           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

       --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.

       --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

           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.

       --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.

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

           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 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).

       --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.

       --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.

           Show short option help.

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

REPORTING BUGS         top

       Report bugs at cryptsetup mailing list
       <> or in Issues project section

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

SEE ALSO         top

       Cryptsetup FAQ

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

CRYPTSETUP         top

       Part of cryptsetup project
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cryptsetup 2.6.1-git           2022-12-14       CRYPTSETU...CHANGEKEY(8)

Pages that refer to this page: cryptsetup(8)