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.
23
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).
42
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.
53
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           With LUKS, the passphrase supplied via --key-file is always the
58           existing passphrase requested by a command, except in the case of
59           luksFormat where --key-file is equivalent to the positional key
60           file argument.
61
62           If you want to set a new passphrase via key file, you have to use a
63           positional argument to luksAddKey.
64
65           See section NOTES ON PASSPHRASE PROCESSING in cryptsetup(8) for
66           more information.
67
68       --keyfile-offset value
69           Skip value bytes at the beginning of the key file.
70
71       --keyfile-size, -l value
72           Read a maximum of value bytes from the key file. The default is to
73           read the whole file up to the compiled-in maximum that can be
74           queried with --help. Supplying more data than the compiled-in
75           maximum aborts the operation.
76
77           This option is useful to cut trailing newlines, for example. If
78           --keyfile-offset is also given, the size count starts after the
79           offset.
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81       --new-keyfile-offset value
82           Skip value bytes at the start when adding a new passphrase from key
83           file with luksAddKey.
84
85       --new-keyfile-size value
86           Read a maximum of value bytes when adding a new passphrase from key
87           file with luksAddKey. The default is to read the whole file up to
88           the compiled-in maximum length that can be queried with --help.
89           Supplying more than the compiled in maximum aborts the operation.
90           When --new-keyfile-offset is also given, reading starts after the
91           offset.
92
93       --key-slot, -S <0-N>
94           For LUKS operations that add key material, this option allows you
95           to specify which key slot is selected for the new key.
96
97           The maximum number of key slots depends on the LUKS version. LUKS1
98           can have up to 8 key slots. LUKS2 can have up to 32 key slots based
99           on key slot area size and key size, but a valid key slot ID can
100           always be between 0 and 31 for LUKS2.
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102       --pbkdf <PBKDF spec>
103           Set Password-Based Key Derivation Function (PBKDF) algorithm for
104           LUKS keyslot. The PBKDF can be: pbkdf2 (for PBKDF2 according to
105           RFC2898), argon2i for Argon2i or argon2id for Argon2id (see Argon2
106           <https://www.cryptolux.org/index.php/Argon2> for more info).
107
108           For LUKS1, only PBKDF2 is accepted (no need to use this option).
109           The default PBKDF for LUKS2 is set during compilation time and is
110           available in cryptsetup --help output.
111
112           A PBKDF is used for increasing dictionary and brute-force attack
113           cost for keyslot passwords. The parameters can be time, memory and
114           parallel cost.
115
116           For PBKDF2, only time cost (number of iterations) applies. For
117           Argon2i/id, there is also memory cost (memory required during the
118           process of key derivation) and parallel cost (number of threads
119           that run in parallel during the key derivation.
120
121           Note that increasing memory cost also increases time, so the final
122           parameter values are measured by a benchmark. The benchmark tries
123           to find iteration time (--iter-time) with required memory cost
124           --pbkdf-memory. If it is not possible, the memory cost is decreased
125           as well. The parallel cost --pbkdf-parallel is constant and is
126           checked against available CPU cores.
127
128           You can see all PBKDF parameters for particular LUKS2 keyslot with
129           cryptsetup-luksDump(8) command.
130
131           NOTE: If you do not want to use benchmark and want to specify all
132           parameters directly, use --pbkdf-force-iterations with
133           --pbkdf-memory and --pbkdf-parallel. This will override the values
134           without benchmarking. Note it can cause extremely long unlocking
135           time. Use only in specific cases, for example, if you know that the
136           formatted device will be used on some small embedded system.
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138           MINIMAL AND MAXIMAL PBKDF COSTS: For PBKDF2, the minimum iteration
139           count is 1000 and maximum is 4294967295 (maximum for 32bit unsigned
140           integer). Memory and parallel costs are unused for PBKDF2. For
141           Argon2i and Argon2id, minimum iteration count (CPU cost) is 4 and
142           maximum is 4294967295 (maximum for 32bit unsigned integer). Minimum
143           memory cost is 32 KiB and maximum is 4 GiB. (Limited by addressable
144           memory on some CPU platforms.) If the memory cost parameter is
145           benchmarked (not specified by a parameter) it is always in range
146           from 64 MiB to 1 GiB. The parallel cost minimum is 1 and maximum 4
147           (if enough CPUs cores are available, otherwise it is decreased).
148
149       --iter-time, -i <number of milliseconds>
150           The number of milliseconds to spend with PBKDF passphrase
151           processing. Specifying 0 as parameter selects the compiled-in
152           default.
153
154       --pbkdf-memory <number>
155           Set the memory cost for PBKDF (for Argon2i/id the number represents
156           kilobytes). Note that it is maximal value, PBKDF benchmark or
157           available physical memory can decrease it. This option is not
158           available for PBKDF2.
159
160       --pbkdf-parallel <number>
161           Set the parallel cost for PBKDF (number of threads, up to 4). Note
162           that it is maximal value, it is decreased automatically if CPU
163           online count is lower. This option is not available for PBKDF2.
164
165       --pbkdf-force-iterations <num>
166           Avoid PBKDF benchmark and set time cost (iterations) directly. It
167           can be used for LUKS/LUKS2 device only. See --pbkdf option for more
168           info.
169
170       --timeout, -t <number of seconds>
171           The number of seconds to wait before timeout on passphrase input
172           via terminal. It is relevant every time a passphrase is asked. It
173           has no effect if used in conjunction with --key-file.
174
175           This option is useful when the system should not stall if the user
176           does not input a passphrase, e.g. during boot. The default is a
177           value of 0 seconds, which means to wait forever.
178
179       --header <device or file storing the LUKS header>
180           Use a detached (separated) metadata device or file where the LUKS
181           header is stored. This option allows one to store ciphertext and
182           LUKS header on different devices.
183
184           For commands that change the LUKS header (e.g. luksAddKey), specify
185           the device or file with the LUKS header directly as the LUKS
186           device.
187
188       --force-password
189           Do not use password quality checking for new LUKS passwords.
190
191           This option is ignored if cryptsetup is built without password
192           quality checking support.
193
194           For more info about password quality check, see the manual page for
195           pwquality.conf(5) and passwdqc.conf(5).
196
197       --disable-locks
198           Disable lock protection for metadata on disk. This option is valid
199           only for LUKS2 and ignored for other formats.
200
201           WARNING: Do not use this option unless you run cryptsetup in a
202           restricted environment where locking is impossible to perform
203           (where /run directory cannot be used).
204
205       --keyslot-cipher <cipher-spec>
206           This option can be used to set specific cipher encryption for the
207           LUKS2 keyslot area.
208
209       --keyslot-key-size <bits>
210           This option can be used to set specific key size for the LUKS2
211           keyslot area.
212
213       --batch-mode, -q
214           Suppresses all confirmation questions. Use with care!
215
216           If the --verify-passphrase option is not specified, this option
217           also switches off the passphrase verification.
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219       --debug or --debug-json
220           Run in debug mode with full diagnostic logs. Debug output lines are
221           always prefixed by #.
222
223           If --debug-json is used, additional LUKS2 JSON data structures are
224           printed.
225
226       --version, -V
227           Show the program version.
228
229       --usage
230           Show short option help.
231
232       --help, -?
233           Show help text and default parameters.
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REPORTING BUGS

236       Report bugs at cryptsetup mailing list <cryptsetup@lists.linux.dev> or
237       in Issues project section
238       <https://gitlab.com/cryptsetup/cryptsetup/-/issues/new>.
239
240       Please attach output of the failed command with --debug option added.
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SEE ALSO

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

249       Part of cryptsetup project <https://gitlab.com/cryptsetup/cryptsetup/>.
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253cryptsetup 2.5.0                  2022-07-28       CRYPTSETUP-LUKSCHANGEKEY(8)
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