1CRYPTSETUP-LUKSCHANGEKEY(8)  Maintenance Commands  CRYPTSETUP-LUKSCHANGEKEY(8)
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NAME

6       cryptsetup-luksChangeKey - change an existing passphrase
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SYNOPSIS

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

12       Changes an existing passphrase. The passphrase to be changed must be
13       supplied interactively or via --key-file. The new passphrase can be
14       supplied interactively or in a file given as the positional argument.
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16       If a key-slot is specified (via --key-slot), the passphrase for that
17       key-slot must be given and the new passphrase will overwrite the
18       specified key-slot. If no key-slot is specified and there is still a
19       free key-slot, then the new passphrase will be put into a free key-slot
20       before the key-slot containing the old passphrase is purged. If there
21       is no free key-slot, then the key-slot with the old passphrase is
22       overwritten directly.
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24       WARNING: If a key-slot is overwritten, a media failure during this
25       operation can cause the overwrite to fail after the old passphrase has
26       been wiped and make the LUKS container inaccessible.
27
28       NOTE: some parameters are effective only if used with LUKS2 format that
29       supports per-keyslot parameters. For LUKS1, PBKDF type and hash
30       algorithm is always the same for all keyslots.
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32       <options> can be [--key-file, --keyfile-offset, --keyfile-size,
33       --new-keyfile-offset, --iter-time, --pbkdf, --pbkdf-force-iterations,
34       --pbkdf-memory, --pbkdf-parallel, --new-keyfile-size, --key-slot,
35       --force-password, --hash, --header, --disable-locks, --type,
36       --keyslot-cipher, --keyslot-key-size, --timeout, --verify-passphrase].
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OPTIONS

39       --type <device-type>
40           Specifies required device type, for more info read BASIC ACTIONS
41           section in cryptsetup(8).
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43       --hash, -h <hash-spec>
44           The specified hash is used for PBKDF2 and AF splitter.
45
46       --verify-passphrase, -y
47           When interactively asking for a passphrase, ask for it twice and
48           complain if both inputs do not match. Ignored on input from file or
49           stdin.
50
51       --key-file, -d name
52           Read the passphrase from file.
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54           If the name given is "-", then the passphrase will be read from
55           stdin. In this case, reading will not stop at newline characters.
56
57           The passphrase supplied via --key-file is always the passphrase for
58           existing keyslot requested by the command.
59
60           If you want to set a new passphrase via key file, you have to use a
61           positional argument or parameter --new-keyfile.
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63           See section NOTES ON PASSPHRASE PROCESSING in cryptsetup(8) for
64           more information.
65
66       --keyfile-offset value
67           Skip value bytes at the beginning of the key file.
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69       --keyfile-size, -l value
70           Read a maximum of value bytes from the key file. The default is to
71           read the whole file up to the compiled-in maximum that can be
72           queried with --help. Supplying more data than the compiled-in
73           maximum aborts the operation.
74
75           This option is useful to cut trailing newlines, for example. If
76           --keyfile-offset is also given, the size count starts after the
77           offset.
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79       --new-keyfile-offset value
80           Skip value bytes at the start when adding a new passphrase from key
81           file.
82
83       --new-keyfile-size value
84           Read a maximum of value bytes when adding a new passphrase from key
85           file. The default is to read the whole file up to the compiled-in
86           maximum length that can be queried with --help. Supplying more than
87           the compiled in maximum aborts the operation. When
88           --new-keyfile-offset is also given, reading starts after the
89           offset.
90
91       --key-slot, -S <0-N>
92           For LUKS operations that add key material, this option allows you
93           to specify which key slot is selected for the new key.
94
95           The maximum number of key slots depends on the LUKS version. LUKS1
96           can have up to 8 key slots. LUKS2 can have up to 32 key slots based
97           on key slot area size and key size, but a valid key slot ID can
98           always be between 0 and 31 for LUKS2.
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100       --pbkdf <PBKDF spec>
101           Set Password-Based Key Derivation Function (PBKDF) algorithm for
102           LUKS keyslot. The PBKDF can be: pbkdf2 (for PBKDF2 according to
103           RFC2898), argon2i for Argon2i or argon2id for Argon2id (see Argon2
104           <https://www.cryptolux.org/index.php/Argon2> for more info).
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106           For LUKS1, only PBKDF2 is accepted (no need to use this option).
107           The default PBKDF for LUKS2 is set during compilation time and is
108           available in cryptsetup --help output.
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110           A PBKDF is used for increasing dictionary and brute-force attack
111           cost for keyslot passwords. The parameters can be time, memory and
112           parallel cost.
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114           For PBKDF2, only time cost (number of iterations) applies. For
115           Argon2i/id, there is also memory cost (memory required during the
116           process of key derivation) and parallel cost (number of threads
117           that run in parallel during the key derivation.
118
119           Note that increasing memory cost also increases time, so the final
120           parameter values are measured by a benchmark. The benchmark tries
121           to find iteration time (--iter-time) with required memory cost
122           --pbkdf-memory. If it is not possible, the memory cost is decreased
123           as well. The parallel cost --pbkdf-parallel is constant and is
124           checked against available CPU cores.
125
126           You can see all PBKDF parameters for particular LUKS2 keyslot with
127           cryptsetup-luksDump(8) command.
128
129           NOTE: If you do not want to use benchmark and want to specify all
130           parameters directly, use --pbkdf-force-iterations with
131           --pbkdf-memory and --pbkdf-parallel. This will override the values
132           without benchmarking. Note it can cause extremely long unlocking
133           time. Use only in specific cases, for example, if you know that the
134           formatted device will be used on some small embedded system.
135
136           MINIMAL AND MAXIMAL PBKDF COSTS: For PBKDF2, the minimum iteration
137           count is 1000 and maximum is 4294967295 (maximum for 32bit unsigned
138           integer). Memory and parallel costs are unused for PBKDF2. For
139           Argon2i and Argon2id, minimum iteration count (CPU cost) is 4 and
140           maximum is 4294967295 (maximum for 32bit unsigned integer). Minimum
141           memory cost is 32 KiB and maximum is 4 GiB. (Limited by addressable
142           memory on some CPU platforms.) If the memory cost parameter is
143           benchmarked (not specified by a parameter) it is always in range
144           from 64 MiB to 1 GiB. The parallel cost minimum is 1 and maximum 4
145           (if enough CPUs cores are available, otherwise it is decreased).
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147       --iter-time, -i <number of milliseconds>
148           The number of milliseconds to spend with PBKDF passphrase
149           processing. Specifying 0 as parameter selects the compiled-in
150           default.
151
152       --pbkdf-memory <number>
153           Set the memory cost for PBKDF (for Argon2i/id the number represents
154           kilobytes). Note that it is maximal value, PBKDF benchmark or
155           available physical memory can decrease it. This option is not
156           available for PBKDF2.
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158       --pbkdf-parallel <number>
159           Set the parallel cost for PBKDF (number of threads, up to 4). Note
160           that it is maximal value, it is decreased automatically if CPU
161           online count is lower. This option is not available for PBKDF2.
162
163       --pbkdf-force-iterations <num>
164           Avoid PBKDF benchmark and set time cost (iterations) directly. It
165           can be used for LUKS/LUKS2 device only. See --pbkdf option for more
166           info.
167
168       --timeout, -t <number of seconds>
169           The number of seconds to wait before timeout on passphrase input
170           via terminal. It is relevant every time a passphrase is asked. It
171           has no effect if used in conjunction with --key-file.
172
173           This option is useful when the system should not stall if the user
174           does not input a passphrase, e.g. during boot. The default is a
175           value of 0 seconds, which means to wait forever.
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177       --header <device or file storing the LUKS header>
178           Use a detached (separated) metadata device or file where the LUKS
179           header is stored. This option allows one to store ciphertext and
180           LUKS header on different devices.
181
182           For commands that change the LUKS header (e.g. luksAddKey), specify
183           the device or file with the LUKS header directly as the LUKS
184           device.
185
186       --force-password
187           Do not use password quality checking for new LUKS passwords.
188
189           This option is ignored if cryptsetup is built without password
190           quality checking support.
191
192           For more info about password quality check, see the manual page for
193           pwquality.conf(5) and passwdqc.conf(5).
194
195       --disable-locks
196           Disable lock protection for metadata on disk. This option is valid
197           only for LUKS2 and ignored for other formats.
198
199           WARNING: Do not use this option unless you run cryptsetup in a
200           restricted environment where locking is impossible to perform
201           (where /run directory cannot be used).
202
203       --keyslot-cipher <cipher-spec>
204           This option can be used to set specific cipher encryption for the
205           LUKS2 keyslot area.
206
207       --keyslot-key-size <bits>
208           This option can be used to set specific key size for the LUKS2
209           keyslot area.
210
211       --batch-mode, -q
212           Suppresses all confirmation questions. Use with care!
213
214           If the --verify-passphrase option is not specified, this option
215           also switches off the passphrase verification.
216
217       --debug or --debug-json
218           Run in debug mode with full diagnostic logs. Debug output lines are
219           always prefixed by #.
220
221           If --debug-json is used, additional LUKS2 JSON data structures are
222           printed.
223
224       --version, -V
225           Show the program version.
226
227       --usage
228           Show short option help.
229
230       --help, -?
231           Show help text and default parameters.
232

REPORTING BUGS

234       Report bugs at cryptsetup mailing list <cryptsetup@lists.linux.dev> or
235       in Issues project section
236       <https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.
237
238       Please attach output of the failed command with --debug option added.
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SEE ALSO

241       Cryptsetup FAQ
242       <https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions>
243
244       cryptsetup(8), integritysetup(8) and veritysetup(8)
245

CRYPTSETUP

247       Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.
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251cryptsetup 2.6.1                  2023-02-10       CRYPTSETUP-LUKSCHANGEKEY(8)
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