x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
CRYPTSETUP-LUKSCHANGEKEY(8) Maintenance Commands CRYPTSETUP-LUKSCHANGEKEY(8)
NAME
cryptsetup-luksChangeKey - change an existing passphrase
SYNOPSIS
cryptsetup luksChangeKey [<options>] <device> [<new key file>]
DESCRIPTION
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].
OPTIONS
--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 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.
--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
<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).
--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.
--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 --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.
--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.
--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).
--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).
--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.
--usage
Show short option help.
--help, -?
Show help text and default parameters.
REPORTING BUGS
Report bugs at cryptsetup mailing list <cryptsetup@lists.linux.dev> or
in Issues project section
<https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.
Please attach output of the failed command with --debug option added.
SEE ALSO
Cryptsetup FAQ
<https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>
cryptsetup(8), integritysetup(8) and veritysetup(8)
CRYPTSETUP
Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.
cryptsetup 2.7.0 2024-08-30 CRYPTSETUP-LUKSCHANGEKEY(8)
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