1CRYPTSETUP-REENCRYPT(8) Maintenance Commands CRYPTSETUP-REENCRYPT(8)
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6 cryptsetup-reencrypt - tool for offline LUKS device re-encryption
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9 cryptsetup-reencrypt <options> <device>
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12 Cryptsetup-reencrypt can be used to change reencryption parameters
13 which otherwise require full on-disk data change (re-encryption).
14 You can regenerate volume key (the real key used in on-disk encryption
16 unclocked by passphrase), cipher, cipher mode.
17 Cryptsetup-reencrypt reencrypts data on LUKS device in-place. During
19 reencryption process the LUKS device is marked unavailable.
20 WARNING: The cryptsetup-reencrypt program is not resistant to hardware
22 or kernel failures during reencryption (you can lose your data in this
23 case).
24 ALWAYS BE SURE YOU HAVE RELIABLE BACKUP BEFORE USING THIS TOOL.
26 The reencryption can be temporarily suspended (by TERM signal or by
27 using ctrl+c) but you need to retain temporary files named
28 LUKS-<uuid>.[log|org|new]. LUKS device is unavailable until reencryp‐
29 tion is finished though.
30 Current working directory must be writable and temporary files created
32 during reencryption must be present.
33 For more info about LUKS see cryptsetup(8).
35
37 To start (or continue) re-encryption for <device> use:
38 cryptsetup-reencrypt <device>
40 <options> can be [--batch-mode, --block-size, --cipher | --keep-key,
42 --debug, --device-size, --hash, --header, --iter-time |
43 --pbkdf-force-iterations, --key-file, --key-size, --key-slot, --key‐
44 file-offset, --keyfile-size, --master-key-file, --tries, --pbkdf,
45 --pbkdf-memory, --pbkdf-parallel, --progress-frequency, --use-directio,
46 --use-random | --use-urandom, --use-fsync, --uuid, --verbose, --write-
47 log]
48 To encrypt data on (not yet encrypted) device, use --new with combina‐
50 tion with --reduce-device-size or with --header option for detached
51 header.
52 To remove encryption from device, use --decrypt.
54 For detailed description of encryption and key file options see crypt‐
56 setup(8) man page.
57 --batch-mode, -q
59 Suppresses all warnings and reencryption progress output.
60 --block-size, -B value
62 Use re-encryption block size of <value> in MiB.
63 Values can be between 1 and 64 MiB.
65 --cipher, -c <cipher-spec>
67 Set the cipher specification string.
68 --debug
70 Run in debug mode with full diagnostic logs. Debug output lines
71 are always prefixed by '#'.
72 --decrypt
74 Remove encryption (decrypt already encrypted device and remove
75 LUKS header).
76 WARNING: This is destructive operation and cannot be reverted.
78 --device-size size[units]
80 Instead of real device size, use specified value.
81 It means that only specified area (from the start of the device
83 to the specified size) will be reencrypted.
84 If no unit suffix is specified, the size is in bytes.
86 Unit suffix can be S for 512 byte sectors, K/M/G/T (or
88 KiB,MiB,GiB,TiB) for units with 1024 base or KB/MB/GB/TB for
89 1000 base (SI scale).
90 WARNING: This is destructive operation.
92 --hash, -h <hash-spec>
94 Specifies the hash used in the LUKS1 key setup scheme and volume
95 key digest.
96 NOTE: if this parameter is not specified, default hash algorithm
98 is always used for new LUKS1 device header.
99 NOTE: with LUKS2 format this option is only relevant when new
101 keyslot pbkdf algorithm is set to PBKDF2 (see --pbkdf).
102 --header <LUKS header file>
104 Use a detached (separated) metadata device or file where the
105 LUKS header is stored. This option allows one to store cipher‐
106 text and LUKS header on different devices.
107 WARNING: There is no check whether the ciphertext device speci‐
109 fied actually belongs to the header given. If used with --new
110 option, the header file will created (or overwritten). Use with
111 care.
112 --iter-time, -i <milliseconds>
114 The number of milliseconds to spend with PBKDF2 passphrase pro‐
115 cessing for the new LUKS header.
116 --keep-key
118 Do not change encryption key, just reencrypt the LUKS header and
119 keyslots.
120 This option can be combined only with --hash, --iter-time,
122 --pbkdf-force-iterations, --pbkdf (LUKS2 only), --pbkdf-memory
123 (Argon2i/id and LUKS2 only) and --pbkdf-parallel (Argon2i/id and
124 LUKS2 only) options.
125 --key-file, -d name
127 Read the passphrase from file.
128 WARNING: --key-file option can be used only if there is only one
130 active keyslot, or alternatively, also if --key-slot option is
131 specified (then all other keyslots will be disabled in new LUKS
132 device).
133 If this option is not used, cryptsetup-reencrypt will ask for
135 all active keyslot passphrases.
136 --key-size, -s <bits>
138 Set key size in bits. The argument has to be a multiple of 8.
139 The possible key-sizes are limited by the cipher and mode used.
141 If you are increasing key size, there must be enough space in
143 the LUKS header for enlarged keyslots (data offset must be large
144 enough) or reencryption cannot be performed.
145 If there is not enough space for keyslots with new key size, you
147 can destructively shrink device with --reduce-device-size
148 option.
149 --key-slot, -S <0-MAX>
151 Specify which key slot is used. For LUKS1, max keyslot number is
152 7. For LUKS2, it's 31.
153 WARNING: All other keyslots will be disabled if this option is
155 used.
156 --keyfile-offset value
158 Skip value bytes at the beginning of the key file.
159 --keyfile-size, -l
161 Read a maximum of value bytes from the key file. Default is to
162 read the whole file up to the compiled-in maximum.
163 --master-key-file
165 Use new volume (master) key stored in a file.
166 --new, -N
168 Create new header (encrypt not yet encrypted device).
169 This option must be used together with --reduce-device-size.
171 WARNING: This is destructive operation and cannot be reverted.
173 --pbkdf
175 Set Password-Based Key Derivation Function (PBKDF) algorithm for
176 LUKS keyslot. The PBKDF can be: pbkdf2, argon2i for Argon2i or
177 argon2id for Argon2id.
178 For LUKS1, only pbkdf2 is accepted (no need to use this option).
180 --pbkdf-force-iterations <num>
182 Avoid PBKDF benchmark and set time cost (iterations) directly.
183 --pbkdf-memory <number>
185 Set the memory cost for PBKDF (for Argon2i/id the number repre‐
186 sents kilobytes). Note that it is maximal value, PBKDF bench‐
187 mark or available physical memory can decrease it. This option
188 is not available for PBKDF2.
189 --pbkdf-parallel <number>
191 Set the parallel cost for PBKDF (number of threads, up to 4).
192 Note that it is maximal value, it is decreased automatically if
193 CPU online count is lower. This option is not available for
194 PBKDF2.
195 --progress-frequency <seconds>
197 Print separate line every <seconds> with reencryption progress.
198 --reduce-device-size size[units]
200 Enlarge data offset to specified value by shrinking device size.
201 This means that last sectors on the original device will be
203 lost, ciphertext data will be effectively shifted by specified
204 number of sectors.
205 It can be useful if you e.g. added some space to underlying par‐
207 tition (so last sectors contains no data).
208 For units suffix see --device-size parameter description.
210 You cannot shrink device more than by 64 MiB (131072 sectors).
212 WARNING: This is destructive operation and cannot be reverted.
214 Use with extreme care - shrunk filesystems are usually unrecov‐
215 erable.
216 --tries, -T
218 Number of retries for invalid passphrase entry.
219 --type <type>
221 Use only while encrypting not yet encrypted device (see --new).
222 Specify LUKS version when performing in-place encryption. If the
224 parameter is omitted default value (LUKS1) is used. Type may be
225 one of: luks (default), luks1 or luks2.
226 --use-directio
228 Use direct-io (O_DIRECT) for all read/write data operations
229 related to block device undergoing reencryption.
230 Useful if direct-io operations perform better than normal
232 buffered operations (e.g. in virtual environments).
233 --use-fsync
235 Use fsync call after every written block. This applies for reen‐
236 cryption log files as well.
237 --use-random
239 --use-urandom
241 Define which kernel random number generator will be used to cre‐
242 ate the volume key.
243 --uuid <uuid>
245 Use only while resuming an interrupted decryption process (see
246 --decrypt).
247 To find out what <uuid> to pass look for temporary files
249 LUKS-<uuid>.[|log|org|new] of the interrupted decryption
250 process.
251 --verbose, -v
253 Print more information on command execution.
254 --version
256 Show the program version.
257 --write-log
259 Update log file after every block write. This can slow down
260 reencryption but will minimize data loss in the case of system
261 crash.
262
265 Cryptsetup-reencrypt returns 0 on success and a non-zero value on
266 error.
267 Error codes are: 1 wrong parameters, 2 no permission, 3 out of memory,
269 4 wrong device specified, 5 device already exists or device is busy.
270
272 Reencrypt /dev/sdb1 (change volume key)
273 cryptsetup-reencrypt /dev/sdb1
274 Reencrypt and also change cipher and cipher mode
276 cryptsetup-reencrypt /dev/sdb1 -c aes-xts-plain64
277 Add LUKS encryption to not yet encrypted device
279 First, be sure you have space added to disk.
281 Or alternatively shrink filesystem in advance.
283 Here we need 4096 512-bytes sectors (enough for 2x128 bit key).
284 fdisk -u /dev/sdb # move sdb1 partition end + 4096 sectors (or
286 use resize2fs or tool for your filesystem and shrink it)
287 cryptsetup-reencrypt /dev/sdb1 --new --reduce-device-size 4096S
289 Remove LUKS encryption completely
291 cryptsetup-reencrypt /dev/sdb1 --decrypt
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296 Report bugs, including ones in the documentation, on the cryptsetup
297 mailing list at <dm-crypt@saout.de> or in the 'Issues' section on LUKS
298 website. Please attach the output of the failed command with the
299 --debug option added.
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302 Cryptsetup-reencrypt was written by Milan Broz <gmazyland@gmail.com>.
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305 Copyright © 2012-2018 Milan Broz
306 Copyright © 2012-2018 Red Hat, Inc.
307 This is free software; see the source for copying conditions. There is
309 NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
310 PURPOSE.
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313 The project website at https://gitlab.com/cryptsetup/cryptsetup
314cryptsetup-reencrypt January 2018 CRYPTSETUP-REENCRYPT(8)