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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REPORTING BUGS | SEE ALSO | CRYPTSETUP |
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CRYPTSETU...CHANGEKEY(8) Maintenance Commands CRYPTSETU...CHANGEKEY(8)
cryptsetup-luksChangeKey - change an existing passphrase
cryptsetup luksChangeKey [<options>] <device> [<new key file>]
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
inaccessible. LUKS2 mitigates that by never overwriting existing
keyslot area as long as there’s a free space in keyslots area at
least for one more LUKS2 keyslot.
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].
--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 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).
--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 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
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 parameter selects the compiled-in
default.
--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.
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.
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-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.
--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.
--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.
--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 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 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).
--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.
--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.
--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.
--type <device-type>
Specifies required device type, for more info read BASIC
ACTIONS section in cryptsetup(8).
--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.
Report bugs at cryptsetup mailing list
<[email protected]> 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 [email protected]. This
page was obtained from the project's upstream Git repository
⟨https://gitlab.com/cryptsetup/cryptsetup.git⟩ on 2024-06-14. (At
that time, the date of the most recent commit that was found in
the repository was 2024-06-11.) 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
[email protected]
cryptsetup 2.8.0-git 2023-12-22 CRYPTSETU...CHANGEKEY(8)
Pages that refer to this page: cryptsetup(8)
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HTML rendering created 2024-06-26 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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