1CRYPTSETUP(8) Maintenance Commands CRYPTSETUP(8)
2
6 cryptsetup - manage plain dm-crypt and LUKS encrypted volumes
7
9 cryptsetup <options> <action> <action args>
10
12 cryptsetup is used to conveniently setup dm-crypt managed device-mapper
13 mappings. These include plain dm-crypt volumes and LUKS volumes. The
14 difference is that LUKS uses a metadata header and can hence offer more
15 features than plain dm-crypt. On the other hand, the header is visible
16 and vulnerable to damage.
17 In addition, cryptsetup provides limited support for the use of loop-
19 AES volumes and for TrueCrypt compatible volumes.
20
23 Unless you understand the cryptographic background well, use LUKS.
24 With plain dm-crypt there are a number of possible user errors that
25 massively decrease security. While LUKS cannot fix them all, it can
26 lessen the impact for many of them.
27
29 A lot of good information on the risks of using encrypted storage, on
30 handling problems and on security aspects can be found in the Crypt‐
31 setup FAQ. Read it. Nonetheless, some risks deserve to be mentioned
32 here.
33 Backup: Storage media die. Encryption has no influence on that. Backup
35 is mandatory for encrypted data as well, if the data has any worth. See
36 the Cryptsetup FAQ for advice on how to do a backup of an encrypted
37 volume.
38 Character encoding: If you enter a passphrase with special symbols, the
40 passphrase can change depending on character encoding. Keyboard set‐
41 tings can also change, which can make blind input hard or impossible.
42 For example, switching from some ASCII 8-bit variant to UTF-8 can lead
43 to a different binary encoding and hence different passphrase seen by
44 cryptsetup, even if what you see on the terminal is exactly the same.
45 It is therefore highly recommended to select passphrase characters only
46 from 7-bit ASCII, as the encoding for 7-bit ASCII stays the same for
47 all ASCII variants and UTF-8.
48 LUKS header: If the header of a LUKS volume gets damaged, all data is
50 permanently lost unless you have a header-backup. If a key-slot is
51 damaged, it can only be restored from a header-backup or if another
52 active key-slot with known passphrase is undamaged. Damaging the LUKS
53 header is something people manage to do with surprising frequency. This
54 risk is the result of a trade-off between security and safety, as LUKS
55 is designed for fast and secure wiping by just overwriting header and
56 key-slot area.
57 Previously used partitions: If a partition was previously used, it is a
59 very good idea to wipe filesystem signatures, data, etc. before creat‐
60 ing a LUKS or plain dm-crypt container on it. For a quick removal of
61 filesystem signatures, use "wipefs". Take care though that this may not
62 remove everything. In particular, MD RAID signatures at the end of a
63 device may survive. It also does not remove data. For a full wipe,
64 overwrite the whole partition before container creation. If you do not
65 know how to do that, the cryptsetup FAQ describes several options.
66
69 The following are valid actions for all supported device types.
70 open <device> <name> --type <device_type>
72 Opens (creates a mapping with) <name> backed by device <device>.
74 Device type can be plain, luks (default), luks1, luks2, loopaes
76 or tcrypt.
77 For backward compatibility there are open command aliases:
79 create (argument-order <name> <device>): open --type plain
81 plainOpen: open --type plain
82 luksOpen: open --type luks
83 loopaesOpen: open --type loopaes
84 tcryptOpen: open --type tcrypt
85 <options> are type specific and are described below for individ‐
87 ual device types. For create, the order of the <name> and
88 <device> options is inverted for historical reasons, all other
89 aliases use the standard <device> <name> order.
90 close <name>
92 Removes the existing mapping <name> and wipes the key from ker‐
94 nel memory.
95 For backward compatibility there are close command aliases:
97 remove, plainClose, luksClose, loopaesClose, tcryptClose (all
98 behaves exactly the same, device type is determined automati‐
99 cally from active device).
100 <options> can be [--deferred]
102 status <name>
105 Reports the status for the mapping <name>.
107 resize <name>
109 Resizes an active mapping <name>.
111 If --size (in 512-bytes sectors) is not specified, the size is
113 computed from the underlying device. For LUKS it is the size of
114 the underlying device without the area reserved for LUKS header
115 (see data payload offset in luksDump command). For plain crypt
116 device, the whole device size is used.
117 Note that this does not change the raw device geometry, it just
119 changes how many sectors of the raw device are represented in
120 the mapped device.
121 If cryptsetup detected volume key for active device loaded in
123 kernel keyring service, resize action would first try to
124 retrieve the key using a token and only if it failed it'd ask
125 for a passphrase to unlock a keyslot (LUKS) or to derive a vol‐
126 ume key again (plain mode). The kernel keyring is used by
127 default for LUKS2 devices.
128 With LUKS2 device additional <options> can be [--token-id,
130 --token-only, --key-slot, --key-file, --keyfile-size, --key‐
131 file-offset, --timeout, --disable-locks, --disable-keyring].
132 refresh <name>
135 Refreshes parameters of active mapping <name>.
137 Updates parameters of active device <name> without need to deac‐
139 tivate the device (and umount filesystem). Currently it supports
140 parameters refresh on following devices: LUKS1, LUKS2 (including
141 authenticated encryption), plain crypt and loopaes.
142 Mandatory parametrs are identical to those of an open action for
144 respective device type.
145 You may change following parameters on all devices
147 --perf-same_cpu_crypt, --perf-submit_from_crypt_cpus and
148 --allow-discards.
149 Refreshing device without any optional parameter will refresh
151 the device with default setting (respective to device type).
152 LUKS2 only:
154 --integrity-no-journal parameter affects only LUKS2 devices with
156 underlying dm-integrity device.
157 Adding option --persistent stores any combination of device
159 parameters above in LUKS2 metadata (only after successful
160 refresh operation).
161 --disable-keyring parameter refreshes a device with volume key
163 passed in dm-crypt driver.
164
167 Plain dm-crypt encrypts the device sector-by-sector with a single, non-
168 salted hash of the passphrase. No checks are performed, no metadata is
169 used. There is no formatting operation. When the raw device is mapped
170 (opened), the usual device operations can be used on the mapped device,
171 including filesystem creation. Mapped devices usually reside in
172 /dev/mapper/<name>.
173 The following are valid plain device type actions:
175 open --type plain <device> <name>
177 create <name> <device> (OBSOLETE syntax)
178 Opens (creates a mapping with) <name> backed by device <device>.
180 <options> can be [--hash, --cipher, --verify-passphrase, --sec‐
182 tor-size, --key-file, --keyfile-offset, --key-size, --offset,
183 --skip, --size, --readonly, --shared, --allow-discards,
184 --refresh]
185 Example: 'cryptsetup open --type plain /dev/sda10 e1' maps the
187 raw encrypted device /dev/sda10 to the mapped (decrypted) device
188 /dev/mapper/e1, which can then be mounted, fsck-ed or have a
189 filesystem created on it.
190
192 LUKS, the Linux Unified Key Setup, is a standard for disk encryption.
193 It adds a standardized header at the start of the device, a key-slot
194 area directly behind the header and the bulk data area behind that. The
195 whole set is called a 'LUKS container'. The device that a LUKS con‐
196 tainer resides on is called a 'LUKS device'. For most purposes, both
197 terms can be used interchangeably. But note that when the LUKS header
198 is at a nonzero offset in a device, then the device is not a LUKS
199 device anymore, but has a LUKS container stored in it at an offset.
200 LUKS can manage multiple passphrases that can be individually revoked
202 or changed and that can be securely scrubbed from persistent media due
203 to the use of anti-forensic stripes. Passphrases are protected against
204 brute-force and dictionary attacks by PBKDF2, which implements hash
205 iteration and salting in one function.
206 LUKS2 is a new version of header format that allows additional exten‐
208 sions like different PBKDF algorithm or authenticated encryption. You
209 can format device with LUKS2 header if you specify --type luks2 in
210 luksFormat command. For activation, the format is already recognized
211 automatically.
212 Each passphrase, also called a key in this document, is associated with
214 one of 8 key-slots. Key operations that do not specify a slot affect
215 the first slot that matches the supplied passphrase or the first empty
216 slot if a new passphrase is added.
217 The <device> parameter can also be specified by a LUKS UUID in the for‐
219 mat UUID=<uuid>. Translation to real device name uses symlinks in
220 /dev/disk/by-uuid directory.
221 To specify a detached header, the --header parameter can be used in all
223 LUKS commands and always takes precedence over the positional <device>
224 parameter.
225 The following are valid LUKS actions:
227 luksFormat <device> [<key file>]
229 Initializes a LUKS partition and sets the initial passphrase
231 (for key-slot 0), either via prompting or via <key file>. Note
232 that if the second argument is present, then the passphrase is
233 taken from the file given there, without the need to use the
234 --key-file option. Also note that for both forms of reading the
235 passphrase from a file you can give '-' as file name, which
236 results in the passphrase being read from stdin and the safety-
237 question being skipped.
238 You can only call luksFormat on a LUKS device that is not
240 mapped.
241 To use LUKS2, specify --type luks2.
243 <options> can be [--hash, --cipher, --verify-passphrase,
245 --key-size, --key-slot, --key-file (takes precedence over
246 optional second argument), --keyfile-offset, --keyfile-size,
247 --use-random | --use-urandom, --uuid, --master-key-file,
248 --iter-time, --header, --pbkdf-force-iterations, --force-pass‐
249 word, --disable-locks].
250 For LUKS2, additional <options> can be [--integrity,
252 --integrity-no-wipe, --sector-size, --label, --subsystem,
253 --pbkdf, --pbkdf-memory, --pbkdf-parallel, --disable-locks,
254 --disable-keyring, --luks2-metadata-size, --luks2-keyslots-size,
255 --keyslot-cipher, --keyslot-key-size].
256 WARNING: Doing a luksFormat on an existing LUKS container will
258 make all data the old container permanently irretrievable unless
259 you have a header backup.
260 open --type luks <device> <name>
262 luksOpen <device> <name> (old syntax)
263 Opens the LUKS device <device> and sets up a mapping <name>
265 after successful verification of the supplied passphrase.
266 First, the passphrase is searched in LUKS tokens. If it's not
268 found in any token and also the passphrase is not supplied via
269 --key-file, the command prompts for it interactively.
270 <options> can be [--key-file, --keyfile-offset, --keyfile-size,
272 --readonly, --test-passphrase, --allow-discards, --header,
273 --key-slot, --master-key-file, --token-id, --token-only, --dis‐
274 able-keyring, --disable-locks, --type, --refresh].
275 luksSuspend <name>
277 Suspends an active device (all IO operations will block and
279 accesses to the device will wait indefinitely) and wipes the
280 encryption key from kernel memory. Needs kernel 2.6.19 or later.
281 After this operation you have to use luksResume to reinstate the
283 encryption key and unblock the device or close to remove the
284 mapped device.
285 WARNING: never suspend the device on which the cryptsetup binary
287 resides.
288 <options> can be [--header, --disable-locks].
290 luksResume <name>
292 Resumes a suspended device and reinstates the encryption key.
294 Prompts interactively for a passphrase if --key-file is not
295 given.
296 <options> can be [--key-file, --keyfile-size, --header, --dis‐
298 able-keyring, --disable-locks, --type]
299 luksAddKey <device> [<key file with new key>]
301 Adds a new passphrase. An existing passphrase must be supplied
303 interactively or via --key-file. The new passphrase to be added
304 can be specified interactively or read from the file given as
305 positional argument.
306 NOTE: with --unbound option the action creates new unbound LUKS2
308 keyslot. The keyslot cannot be used for device activation. If
309 you don't pass new key via --master-key-file option, new random
310 key is generated. Existing passphrase for any active keyslot is
311 not required.
312 <options> can be [--key-file, --keyfile-offset, --keyfile-size,
314 --new-keyfile-offset, --new-keyfile-size, --key-slot, --mas‐
315 ter-key-file, --iter-time, --force-password, --header, --dis‐
316 able-locks, --unbound, --type, --keyslot-cipher,
317 --keyslot-key-size].
318 luksRemoveKey <device> [<key file with passphrase to be removed>]
320 Removes the supplied passphrase from the LUKS device. The
322 passphrase to be removed can be specified interactively, as the
323 positional argument or via --key-file.
324 <options> can be [--key-file, --keyfile-offset, --keyfile-size,
326 --header, --disable-locks, --type]
327 WARNING: If you read the passphrase from stdin (without further
329 argument or with '-' as an argument to --key-file), batch-mode
330 (-q) will be implicitly switched on and no warning will be given
331 when you remove the last remaining passphrase from a LUKS con‐
332 tainer. Removing the last passphrase makes the LUKS container
333 permanently inaccessible.
334 luksChangeKey <device> [<new key file>]
336 Changes an existing passphrase. The passphrase to be changed
338 must be supplied interactively or via --key-file. The new
339 passphrase can be supplied interactively or in a file given as
340 positional argument.
341 If a key-slot is specified (via --key-slot), the passphrase for
343 that key-slot must be given and the new passphrase will over‐
344 write the specified key-slot. If no key-slot is specified and
345 there is still a free key-slot, then the new passphrase will be
346 put into a free key-slot before the key-slot containing the old
347 passphrase is purged. If there is no free key-slot, then the
348 key-slot with the old passphrase is overwritten directly.
349 WARNING: If a key-slot is overwritten, a media failure during
351 this operation can cause the overwrite to fail after the old
352 passphrase has been wiped and make the LUKS container inaccessi‐
353 ble.
354 <options> can be [--key-file, --keyfile-offset, --keyfile-size,
356 --new-keyfile-offset, --new-keyfile-size, --key-slot,
357 --force-password, --header, --disable-locks, --type,
358 --keyslot-cipher, --keyslot-key-size].
359 luksConvertKey <device>
361 Converts an existing LUKS2 keyslot to new pbkdf parameters. The
363 passphrase for keyslot to be converted must be supplied interac‐
364 tively or via --key-file. If no --pbkdf parameters are specified
365 LUKS2 default pbkdf values will apply.
366 If a keyslot is specified (via --key-slot), the passphrase for
368 that keyslot must be given. If no keyslot is specified and there
369 is still a free keyslot, then the new parameters will be put
370 into a free keyslot before the keyslot containing the old param‐
371 eters is purged. If there is no free keyslot, then the keyslot
372 with the old parameters is overwritten directly.
373 WARNING: If a keyslot is overwritten, a media failure during
375 this operation can cause the overwrite to fail after the old
376 parameters have been wiped and make the LUKS container inacces‐
377 sible.
378 <options> can be [--key-file, --keyfile-offset, --keyfile-size,
380 --key-slot, --header, --disable-locks, --iter-time, --pbkdf,
381 --pbkdf-force-iterations, --pbkdf-memory, --pbkdf-parallel,
382 --keyslot-cipher, --keyslot-key-size].
383 luksKillSlot <device> <key slot number>
385 Wipe the key-slot number <key slot> from the LUKS device. Except
387 running in batch-mode (-q) a remaining passphrase must be sup‐
388 plied, either interactively or via --key-file. This command can
389 remove the last remaining key-slot, but requires an interactive
390 confirmation when doing so. Removing the last passphrase makes a
391 LUKS container permanently inaccessible.
392 <options> can be [--key-file, --keyfile-offset, --keyfile-size,
394 --header, --disable-locks, --type].
395 WARNING: If you read the passphrase from stdin (without further
397 argument or with '-' as an argument to --key-file), batch-mode
398 (-q) will be implicitly switched on and no warning will be given
399 when you remove the last remaining passphrase from a LUKS con‐
400 tainer. Removing the last passphrase makes the LUKS container
401 permanently inaccessible.
402 NOTE: If there is no passphrase provided (on stdin or through
404 --key-file argument) and batch-mode (-q) is active, the key-slot
405 is removed without any other warning.
406 erase <device>
409 luksErase <device>
410 Erase all keyslots and make the LUKS container permanently inac‐
412 cessible. You do not need to provide any password for this
413 operation.
414 WARNING: This operation is irreversible.
416 luksUUID <device>
418 Print the UUID of a LUKS device.
420 Set new UUID if --uuid option is specified.
421 isLuks <device>
423 Returns true, if <device> is a LUKS device, false otherwise.
425 Use option -v to get human-readable feedback. 'Command success‐
426 ful.' means the device is a LUKS device.
427 By specifying --type you may query for specific LUKS version.
429 luksDump <device>
431 Dump the header information of a LUKS device.
433 If the --dump-master-key option is used, the LUKS device master
435 key is dumped instead of the keyslot info. Together with --mas‐
436 ter-key-file option, master key is dumped to a file instead of
437 standard output. Beware that the master key cannot be changed
438 without reencryption and can be used to decrypt the data stored
439 in the LUKS container without a passphrase and even without the
440 LUKS header. This means that if the master key is compromised,
441 the whole device has to be erased to prevent further access. Use
442 this option carefully.
443 To dump the master key, a passphrase has to be supplied, either
445 interactively or via --key-file.
446 <options> can be [--dump-master-key, --key-file, --keyfile-off‐
448 set, --keyfile-size, --header, --disable-locks, --mas‐
449 ter-key-file, --type].
450 WARNING: If --dump-master-key is used with --key-file and the
452 argument to --key-file is '-', no validation question will be
453 asked and no warning given.
454 luksHeaderBackup <device> --header-backup-file <file>
456 Stores a binary backup of the LUKS header and keyslot area.
458 Note: Using '-' as filename writes the header backup to a file
459 named '-'.
460 WARNING: This backup file and a passphrase valid at the time of
462 backup allows decryption of the LUKS data area, even if the
463 passphrase was later changed or removed from the LUKS device.
464 Also note that with a header backup you lose the ability to
465 securely wipe the LUKS device by just overwriting the header and
466 key-slots. You either need to securely erase all header backups
467 in addition or overwrite the encrypted data area as well. The
468 second option is less secure, as some sectors can survive, e.g.
469 due to defect management.
470 luksHeaderRestore <device> --header-backup-file <file>
472 Restores a binary backup of the LUKS header and keyslot area
474 from the specified file.
475 Note: Using '-' as filename reads the header backup from a file
476 named '-'.
477 WARNING: Header and keyslots will be replaced, only the
479 passphrases from the backup will work afterward.
480 This command requires that the master key size and data offset
482 of the LUKS header already on the device and of the header
483 backup match. Alternatively, if there is no LUKS header on the
484 device, the backup will also be written to it.
485 token <add|remove|import|export> <device>
487 Action add creates new keyring token to enable auto-activation
489 of the device. For the auto-activation, the passphrase must be
490 stored in keyring with the specified description. Usually, the
491 passphrase should be stored in user or user-session keyring.
492 The token command is supported only for LUKS2.
493 For adding new keyring token, option --key-description is manda‐
495 tory. Also, new token is assigned to key slot specified with
496 --key-slot option or to all active key slots in the case
497 --key-slot option is omitted.
498 To remove existing token, specify the token ID which should be
500 removed with --token-id option.
501 WARNING: The action token remove removes any token type, not
503 just keyring type from token slot specified by --token-id
504 option.
505 Action import can store arbitrary valid token json in LUKS2
507 header. It may be passed via standard input or via file passed
508 in --json-file option. If you specify --key-slot then success‐
509 fully imported token is also assigned to the key slot.
510 Action export writes requested token json to a file passed with
512 --json-file or to standard output.
513 <options> can be [--header, --token-id, --key-slot,
515 --key-description, --disable-locks, --disable-keyring,
516 --json-file].
517 convert <device> --type <format>
519 Converts the device between LUKS1 and LUKS2 format (if possi‐
521 ble). The conversion will not be performed if there is an addi‐
522 tional LUKS2 feature or LUKS1 has unsupported header size.
523 Conversion (both directions) must be performed on inactive
525 device. There must not be active dm-crypt mapping established
526 for LUKS header requested for conversion.
527 --type option is mandatory with following accepted values: luks1
529 or luks2.
530 WARNING: The convert action can destroy the LUKS header in the
532 case of a crash during conversion or if a media error occurs.
533 Always create a header backup before performing this operation!
534 <options> can be [--header, --type].
536 config <device>
538 Set permanent configuration options (store to LUKS header). The
540 config command is supported only for LUKS2.
541 The permanent options can be --priority to set priority (normal,
543 prefer, ignore) for keyslot (specified by --key-slot) or --label
544 and --subsystem.
545 <options> can be [--priority, --label, --subsystem, --key-slot,
547 --header].
548
551 cryptsetup supports mapping loop-AES encrypted partition using a com‐
552 patibility mode.
553 open --type loopaes <device> <name> --key-file <keyfile>
555 loopaesOpen <device> <name> --key-file <keyfile> (old syntax)
556 Opens the loop-AES <device> and sets up a mapping <name>.
558 If the key file is encrypted with GnuPG, then you have to use
560 --key-file=- and decrypt it before use, e.g. like this:
561 gpg --decrypt <keyfile> | cryptsetup loopaesOpen --key-file=-
562 <device> <name>
563 WARNING: The loop-AES extension cannot use the direct input of
565 key file on real terminal because the keys are separated by end-
566 of-line and only part of the multi-key file would be read.
567 If you need it in script, just use the pipe redirection:
568 echo $keyfile | cryptsetup loopaesOpen --key-file=- <device>
569 <name>
570 Use --keyfile-size to specify the proper key length if needed.
572 Use --offset to specify device offset. Note that the units need
574 to be specified in number of 512 byte sectors.
575 Use --skip to specify the IV offset. If the original device used
577 an offset and but did not use it in IV sector calculations, you
578 have to explicitly use --skip 0 in addition to the offset param‐
579 eter.
580 Use --hash to override the default hash function for passphrase
582 hashing (otherwise it is detected according to key size).
583 <options> can be [--key-file, --key-size, --offset, --skip,
585 --hash, --readonly, --allow-discards, --refresh].
586 See also section 7 of the FAQ and http://loop-aes.sourceforge.net for
588 more information regarding loop-AES.
589
591 cryptsetup supports mapping of TrueCrypt, tcplay or VeraCrypt (with
592 --veracrypt option) encrypted partition using a native Linux kernel
593 API. Header formatting and TCRYPT header change is not supported,
594 cryptsetup never changes TCRYPT header on-device.
595 TCRYPT extension requires kernel userspace crypto API to be available
597 (introduced in Linux kernel 2.6.38). If you are configuring kernel
598 yourself, enable "User-space interface for symmetric key cipher algo‐
599 rithms" in "Cryptographic API" section (CRYPTO_USER_API_SKCIPHER .con‐
600 fig option).
601 Because TCRYPT header is encrypted, you have to always provide valid
603 passphrase and keyfiles.
604 Cryptsetup should recognize all header variants, except legacy cipher
606 chains using LRW encryption mode with 64 bits encryption block (namely
607 Blowfish in LRW mode is not recognized, this is limitation of kernel
608 crypto API).
609 To recognize a VeraCrypt device use the --veracrypt option. VeraCrypt
611 is just extension of TrueCrypt header with increased iteration count so
612 unlocking can take quite a lot of time (in comparison with TCRYPT
613 device).
614 To open a VeraCrypt device with a custom Personal Iteration Multiplier
616 (PIM) value, additionally to --veracrypt use either the --ver‐
617 acrypt-pim=<PIM> option to directly specify the PIM on the command-
618 line or use --veracrypt-query-pim to be prompted for the PIM.
619 The PIM value affects the number of iterations applied during key
621 derivation. Please refer to https://www.veracrypt.fr/en/Per‐
622 sonal%20Iterations%20Multiplier%20%28PIM%29.html for more detailed
623 information.
624 NOTE: Activation with tcryptOpen is supported only for cipher chains
626 using LRW or XTS encryption modes.
627 The tcryptDump command should work for all recognized TCRYPT devices
629 and doesn't require superuser privilege.
630 To map system device (device with boot loader where the whole encrypted
632 system resides) use --tcrypt-system option. You can use partition
633 device as the parameter (parameter must be real partition device, not
634 an image in a file), then only this partition is mapped.
635 If you have the whole TCRYPT device as a file image and you want to map
637 multiple partition encrypted with system encryption, please create
638 loopback mapping with partitions first (losetup -P, see losetup(8) man
639 page for more info), and use loop partition as the device parameter.
640 If you use the whole base device as a parameter, one device for the
642 whole system encryption is mapped. This mode is available only for
643 backward compatibility with older cryptsetup versions which mapped
644 TCRYPT system encryption using the whole device.
645 To use hidden header (and map hidden device, if available), use
647 --tcrypt-hidden option.
648 To explicitly use backup (secondary) header, use --tcrypt-backup
650 option.
651 NOTE: There is no protection for a hidden volume if the outer volume is
653 mounted. The reason is that if there were any protection, it would
654 require some metadata describing what to protect in the outer volume
655 and the hidden volume would become detectable.
656 open --type tcrypt <device> <name>
659 tcryptOpen <device> <name> (old syntax)
660 Opens the TCRYPT (a TrueCrypt-compatible) <device> and sets up a
662 mapping <name>.
663 <options> can be [--key-file, --tcrypt-hidden, --tcrypt-system,
665 --tcrypt-backup, --readonly, --test-passphrase, --allow-dis‐
666 cards, --veracrypt, --veracrypt-pim, --veracrypt-query-pim].
667 The keyfile parameter allows a combination of file content with
669 the passphrase and can be repeated. Note that using keyfiles is
670 compatible with TCRYPT and is different from LUKS keyfile logic.
671 WARNING: Option --allow-discards cannot be combined with option
673 --tcrypt-hidden. For normal mapping, it can cause the destruc‐
674 tion of hidden volume (hidden volume appears as unused space for
675 outer volume so this space can be discarded).
676 tcryptDump <device>
679 Dump the header information of a TCRYPT device.
681 If the --dump-master-key option is used, the TCRYPT device mas‐
683 ter key is dumped instead of TCRYPT header info. Beware that the
684 master key (or concatenated master keys if cipher chain is used)
685 can be used to decrypt the data stored in the TCRYPT container
686 without a passphrase. This means that if the master key is com‐
687 promised, the whole device has to be erased to prevent further
688 access. Use this option carefully.
689 <options> can be [--dump-master-key, --key-file, --tcrypt-hid‐
691 den, --tcrypt-system, --tcrypt-backup].
692 The keyfile parameter allows a combination of file content with
694 the passphrase and can be repeated.
695 See also https://en.wikipedia.org/wiki/TrueCrypt for more information
697 regarding TrueCrypt.
698 Please note that cryptsetup does not use TrueCrypt code, please report
700 all problems related to this compatibility extension to the cryptsetup
701 project.
702
704 repair <device>
705 Tries to repair the device metadata if possible. Currently sup‐
707 ported only for LUKS device type.
708 This command is useful to fix some known benign LUKS metadata
710 header corruptions. Only basic corruptions of unused keyslot are
711 fixable. This command will only change the LUKS header, not any
712 key-slot data. You may enforce LUKS version by adding --type
713 option.
714 WARNING: Always create a binary backup of the original header
716 before calling this command.
717 benchmark <options>
719 Benchmarks ciphers and KDF (key derivation function). Without
721 parameters, it tries to measure few common configurations.
722 To benchmark other ciphers or modes, you need to specify
724 --cipher and --key-size options or --hash for KDF test.
725 NOTE: This benchmark is using memory only and is only informa‐
727 tive. You cannot directly predict real storage encryption speed
728 from it.
729 For testing block ciphers, this benchmark requires kernel
731 userspace crypto API to be available (introduced in Linux kernel
732 2.6.38). If you are configuring kernel yourself, enable "User-
733 space interface for symmetric key cipher algorithms" in "Crypto‐
734 graphic API" section (CRYPTO_USER_API_SKCIPHER .config option).
735 <options> can be [--cipher, --key-size, --hash].
737
739 --verbose, -v
740 Print more information on command execution.
741 --debug or --debug-json
743 Run in debug mode with full diagnostic logs. Debug output lines
744 are always prefixed by '#'. If --debug-json is used, additional
745 LUKS2 JSON data structures are printed.
746 --type <device-type>
748 Specifies required device type, for more info read BASIC COM‐
749 MANDS section.
750 --hash, -h <hash-spec>
752 Specifies the passphrase hash for open (for plain and loopaes
753 device types).
754 Specifies the hash used in the LUKS key setup scheme and volume
756 key digest for luksFormat. The specified hash is used as hash-
757 parameter for PBKDF2 and for the AF splitter.
758 The specified hash name is passed to the compiled-in crypto
760 backend. Different backends may support different hashes. For
761 luksFormat, the hash algorithm must provide at least 160 bits of
762 output, which excludes, e.g., MD5. Do not use a non-crypto hash
763 like "crc32" as this breaks security.
764 Values compatible with old version of cryptsetup are "ripemd160"
766 for open --type plain and "sha1" for luksFormat.
767 Use cryptsetup --help to show the defaults.
769 --cipher, -c <cipher-spec>
771 Set the cipher specification string.
772 cryptsetup --help shows the compiled-in defaults. The current
774 default in the distributed sources is "aes-cbc-essiv:sha256" for
775 plain dm-crypt and "aes-xts-plain64" for LUKS.
776 If a hash is part of the cipher specification, then it is used
778 as part of the IV generation. For example, ESSIV needs a hash
779 function, while "plain64" does not and hence none is specified.
780 For XTS mode you can optionally set a key size of 512 bits with
782 the -s option. Key size for XTS mode is twice that for other
783 modes for the same security level.
784 XTS mode requires kernel 2.6.24 or later and plain64 requires
786 kernel 2.6.33 or later. More information can be found in the
787 FAQ.
788 --verify-passphrase, -y
790 When interactively asking for a passphrase, ask for it twice and
791 complain if both inputs do not match. Advised when creating a
792 regular mapping for the first time, or when running luksFormat.
793 Ignored on input from file or stdin.
794 --key-file, -d name
796 Read the passphrase from file.
797 If the name given is "-", then the passphrase will be read from
799 stdin. In this case, reading will not stop at newline charac‐
800 ters.
801 With LUKS, passphrases supplied via --key-file are always the
803 existing passphrases requested by a command, except in the case
804 of luksFormat where --key-file is equivalent to the positional
805 key file argument.
806 If you want to set a new passphrase via key file, you have to
808 use a positional argument to luksAddKey.
809 See section NOTES ON PASSPHRASE PROCESSING for more information.
811 --keyfile-offset value
813 Skip value bytes at the beginning of the key file. Works with
814 all commands that accept key files.
815 --keyfile-size, -l value
817 Read a maximum of value bytes from the key file. The default is
818 to read the whole file up to the compiled-in maximum that can be
819 queried with --help. Supplying more data than the compiled-in
820 maximum aborts the operation.
821 This option is useful to cut trailing newlines, for example. If
823 --keyfile-offset is also given, the size count starts after the
824 offset. Works with all commands that accept key files.
825 --new-keyfile-offset value
827 Skip value bytes at the start when adding a new passphrase from
828 key file with luksAddKey.
829 --new-keyfile-size value
831 Read a maximum of value bytes when adding a new passphrase from
832 key file with luksAddKey. The default is to read the whole file
833 up to the compiled-in maximum length that can be queried with
834 --help. Supplying more than the compiled in maximum aborts the
835 operation. When --new-keyfile-offset is also given, reading
836 starts after the offset.
837 --master-key-file
839 Use a master key stored in a file.
840 For luksFormat this allows creating a LUKS header with this spe‐
842 cific master key. If the master key was taken from an existing
843 LUKS header and all other parameters are the same, then the new
844 header decrypts the data encrypted with the header the master
845 key was taken from.
846 Action luksDump together with --dump-master-key option: The vol‐
848 ume (master) key is stored in a file instead of being printed
849 out to standard output.
850 WARNING: If you create your own master key, you need to make
852 sure to do it right. Otherwise, you can end up with a low-
853 entropy or otherwise partially predictable master key which will
854 compromise security.
855 For luksAddKey this allows adding a new passphrase without hav‐
857 ing to know an existing one.
858 For open this allows one to open the LUKS device without giving
860 a passphrase.
861 --dump-master-key
863 For luksDump this option includes the master key in the dis‐
864 played information. Use with care, as the master key can be used
865 to bypass the passphrases, see also option --master-key-file.
866 --json-file
868 Read token json from a file or write token to it. See token
869 action for more information. --json-file=- reads json from stan‐
870 dard input or writes it to standard output respectively.
871 --use-random
873 --use-urandom
875 For luksFormat these options define which kernel random number
876 generator will be used to create the master key (which is a
877 long-term key).
878 See NOTES ON RANDOM NUMBER GENERATORS for more information. Use
880 cryptsetup --help to show the compiled-in default random number
881 generator.
882 WARNING: In a low-entropy situation (e.g. in an embedded sys‐
884 tem), both selections are problematic. Using /dev/urandom can
885 lead to weak keys. Using /dev/random can block a long time,
886 potentially forever, if not enough entropy can be harvested by
887 the kernel.
888 --key-slot, -S <0-7>
890 For LUKS operations that add key material, this options allows
891 you to specify which key slot is selected for the new key. This
892 option can be used for luksFormat, and luksAddKey.
893 In addition, for open, this option selects a specific key-slot
894 to compare the passphrase against. If the given passphrase
895 would only match a different key-slot, the operation fails.
896 --key-size, -s <bits>
898 Sets key size in bits. The argument has to be a multiple of 8.
899 The possible key-sizes are limited by the cipher and mode used.
900 See /proc/crypto for more information. Note that key-size in
902 /proc/crypto is stated in bytes.
903 This option can be used for open --type plain or luksFormat.
905 All other LUKS actions will use the key-size specified in the
906 LUKS header. Use cryptsetup --help to show the compiled-in
907 defaults.
908 --size, -b <number of 512 byte sectors>
910 Set the size of the device in sectors of 512 bytes. This option
911 is only relevant for the open and resize actions.
912 --offset, -o <number of 512 byte sectors>
914 Start offset in the backend device in 512-byte sectors. This
915 option is only relevant for the open action with plain or
916 loopaes device types or for LUKS devices in luksFormat.
917 For LUKS, the --offset option sets the data offset (payload) of
919 data device and must be be aligned to 4096-byte sectors (must be
920 multiple of 8). This option cannot be combined with
921 --align-payload option.
922 --skip, -p <number of 512 byte sectors>
924 Start offset used in IV calculation in 512-byte sectors (how
925 many sectors of the encrypted data to skip at the beginning).
926 This option is only relevant for the open action with plain or
927 loopaes device types.
928 Hence, if --offset n, and --skip s, sector n (the first sector
930 of the encrypted device) will get a sector number of s for the
931 IV calculation.
932 --readonly, -r
934 set up a read-only mapping.
935 --shared
937 Creates an additional mapping for one common ciphertext device.
938 Arbitrary mappings are supported. This option is only relevant
939 for the open --type plain action. Use --offset, --size and
940 --skip to specify the mapped area.
941 --pbkdf <PBKDF spec>
943 Set Password-Based Key Derivation Function (PBKDF) algorithm for
944 LUKS keyslot. The PBKDF can be: pbkdf2 (for PBKDF2 according to
945 RFC2898), argon2i for Argon2i or argon2id for Argon2id (see
946 https://www.cryptolux.org/index.php/Argon2 for more info).
947 For LUKS1, only PBKDF2 is accepted (no need to use this option).
949 The default PBKDF2 for LUKS2 is set during compilation time and
950 is available in cryptsetup --help output.
951 A PBKDF is used for increasing dictionary and brute-force attack
953 cost for keyslot passwords. The parameters can be time, memory
954 and parallel cost.
955 For PBKDF2, only time cost (number of iterations) applies. For
957 Argon2i/id, there is also memory cost (memory required during
958 the process of key derivation) and parallel cost (number of
959 threads that run in parallel during the key derivation.
960 Note that increasing memory cost also increases time, so the
962 final parameter values are measured by a benchmark. The bench‐
963 mark tries to find iteration time (--iter-time) with required
964 memory cost --pbkdf-memory. If it is not possible, the memory
965 cost is decreased as well. The parallel cost --pbkdf-parallel
966 is constant, is is checked against available CPU cores (if not
967 available, it is decreased) and the maximum parallel cost is 4.
968 You can see all PBKDF parameters for particular LUKS2 keyslot
970 with luksDump command.
971 NOTE: If you do not want to use benchmark and want to specify
973 all parameters directly, use --pbkdf-force-iterations with
974 --pbkdf-memory and --pbkdf-parallel. This will override the
975 values without benchmarking. Note it can cause extremely long
976 unlocking time. Use only is specified cases, for example, if you
977 know that the formatted device will be used on some small embed‐
978 ded system. In this case, the LUKS PBKDF2 digest will be set to
979 the minimum iteration count.
980 --iter-time, -i <number of milliseconds>
982 The number of milliseconds to spend with PBKDF passphrase pro‐
983 cessing. This option is only relevant for LUKS operations that
984 set or change passphrases, such as luksFormat or luksAddKey.
985 Specifying 0 as parameter selects the compiled-in default.
986 --pbkdf-memory <number>
988 Set the memory cost for PBKDF (for Argon2i/id the number repre‐
989 sents kilobytes). Note that it is maximal value, PBKDF bench‐
990 mark or available physical memory can decrease it. This option
991 is not available for PBKDF2.
992 --pbkdf-parallel <number>
994 Set the parallel cost for PBKDF (number of threads, up to 4).
995 Note that it is maximal value, it is decreased automatically if
996 CPU online count is lower. This option is not available for
997 PBKDF2.
998 --pbkdf-force-iterations <num>
1000 Avoid PBKDF benchmark and set time cost (iterations) directly.
1001 It can be used for LUKS/LUKS2 device only. See --pbkdf option
1002 for more info.
1003 --batch-mode, -q
1005 Suppresses all confirmation questions. Use with care!
1006 If the -y option is not specified, this option also switches off
1008 the passphrase verification for luksFormat.
1009 --progress-frequency <seconds>
1011 Print separate line every <seconds> with wipe progress.
1012 --timeout, -t <number of seconds>
1014 The number of seconds to wait before timeout on passphrase input
1015 via terminal. It is relevant every time a passphrase is asked,
1016 for example for open, luksFormat or luksAddKey. It has no
1017 effect if used in conjunction with --key-file.
1018 This option is useful when the system should not stall if the
1019 user does not input a passphrase, e.g. during boot. The default
1020 is a value of 0 seconds, which means to wait forever.
1021 --tries, -T
1023 How often the input of the passphrase shall be retried. This
1024 option is relevant every time a passphrase is asked, for example
1025 for open, luksFormat or luksAddKey. The default is 3 tries.
1026 --align-payload <number of 512 byte sectors>
1028 Align payload at a boundary of value 512-byte sectors. This
1029 option is relevant for luksFormat.
1030 If not specified, cryptsetup tries to use the topology info pro‐
1032 vided by the kernel for the underlying device to get the optimal
1033 alignment. If not available (or the calculated value is a mul‐
1034 tiple of the default) data is by default aligned to a 1MiB
1035 boundary (i.e. 2048 512-byte sectors).
1036 For a detached LUKS header, this option specifies the offset on
1038 the data device. See also the --header option.
1039 WARNING: This option is DEPRECATED and has often unexpected
1041 impact to the data offset and keyslot area size (for LUKS2) due
1042 to the complex rounding. For fixed data device offset use
1043 --offset option instead.
1044 --uuid=UUID
1047 Use the provided UUID for the luksFormat command instead of gen‐
1048 erating a new one. Changes the existing UUID when used with the
1049 luksUUID command.
1050 The UUID must be provided in the standard UUID format, e.g.
1052 12345678-1234-1234-1234-123456789abc.
1053 --allow-discards
1055 Allow the use of discard (TRIM) requests for the device. This
1056 option is only relevant for open action.
1057 WARNING: This command can have a negative security impact
1059 because it can make filesystem-level operations visible on the
1060 physical device. For example, information leaking filesystem
1061 type, used space, etc. may be extractable from the physical
1062 device if the discarded blocks can be located later. If in
1063 doubt, do not use it.
1064 A kernel version of 3.1 or later is needed. For earlier kernels,
1066 this option is ignored.
1067 --perf-same_cpu_crypt
1069 Perform encryption using the same cpu that IO was submitted on.
1070 The default is to use an unbound workqueue so that encryption
1071 work is automatically balanced between available CPUs. This
1072 option is only relevant for open action.
1073 NOTE: This option is available only for low-level dm-crypt per‐
1075 formance tuning, use only if you need a change to default dm-
1076 crypt behaviour. Needs kernel 4.0 or later.
1077 --perf-submit_from_crypt_cpus
1079 Disable offloading writes to a separate thread after encryption.
1080 There are some situations where offloading write bios from the
1081 encryption threads to a single thread degrades performance sig‐
1082 nificantly. The default is to offload write bios to the same
1083 thread. This option is only relevant for open action.
1084 NOTE: This option is available only for low-level dm-crypt per‐
1086 formance tuning, use only if you need a change to default dm-
1087 crypt behaviour. Needs kernel 4.0 or later.
1088 --test-passphrase
1090 Do not activate the device, just verify passphrase. This option
1091 is only relevant for open action (the device mapping name is not
1092 mandatory if this option is used).
1093 --header <device or file storing the LUKS header>
1095 Use a detached (separated) metadata device or file where the
1096 LUKS header is stored. This option allows one to store cipher‐
1097 text and LUKS header on different devices.
1098 This option is only relevant for LUKS devices and can be used
1100 with the luksFormat, open, luksSuspend, luksResume, status and
1101 resize commands.
1102 For luksFormat with a file name as the argument to --header, the
1104 file will be automatically created if it does not exist. See
1105 the cryptsetup FAQ for header size calculation.
1106 For other commands that change the LUKS header (e.g. luksAdd‐
1108 Key), specify the device or file with the LUKS header directly
1109 as the LUKS device.
1110 If used with luksFormat, the --align-payload option is taken as
1112 absolute sector alignment on ciphertext device and can be zero.
1113 WARNING: There is no check whether the ciphertext device speci‐
1115 fied actually belongs to the header given. In fact, you can
1116 specify an arbitrary device as the ciphertext device for open
1117 with the --header option. Use with care.
1118 --header-backup-file <file>
1120 Specify file with header backup for luksHeaderBackup or luk‐
1121 sHeaderBackup actions.
1122 --force-password
1124 Do not use password quality checking for new LUKS passwords.
1125 This option applies only to luksFormat, luksAddKey and
1127 luksChangeKey and is ignored if cryptsetup is built without
1128 password quality checking support.
1129 For more info about password quality check, see the manual page
1131 for pwquality.conf(5) and passwdqc.conf(5).
1132 --deferred
1134 Defers device removal in close command until the last user
1135 closes it.
1136 --disable-locks
1138 Disable lock protection for metadata on disk. This option is
1139 valid only for LUKS2 and ignored for other formats.
1140 WARNING: Do not use this option unless you run cryptsetup in a
1142 restricted environment where locking is impossible to perform
1143 (where /run directory cannot be used).
1144 --disable-keyring
1146 Do not load volume key in kernel keyring but use store key
1147 directly in the dm-crypt target. This option is supported only
1148 for the LUKS2 format.
1149 --key-description <text>
1151 Set key description in keyring for use with token command.
1152 --priority <normal|prefer|ignore>
1154 Set a priority for LUKS2 keyslot. The prefer priority marked
1155 slots are tried before normal priority. The ignored priority
1156 means, that slot is never used, if not explicitly requested by
1157 --key-slot option.
1158 --token-id
1160 Specify what token to use in actions token, open or resize. If
1161 omitted, all available tokens will be checked before proceeding
1162 further with passphrase prompt.
1163 --token-only
1165 Do not proceed further with action (any of token, open or
1166 resize) if token activation failed. Without the option, action
1167 asks for passphrase to proceed further.
1168 --sector-size <bytes>
1170 Set sector size for use with disk encryption. It must be power
1171 of two and in range 512 - 4096 bytes. The default is 512 bytes
1172 sectors. This option is available only in the LUKS2 mode.
1173 Note that if sector size is higher than underlying device hard‐
1175 ware sector and there is not integrity protection that uses data
1176 journal, using this option can increase risk on incomplete sec‐
1177 tor writes during a power fail.
1178 If used together with --integrity option and dm-integrity jour‐
1180 nal, the atomicity of writes is guaranteed in all cases (but it
1181 cost write performance - data has to be written twice).
1182 Increasing sector size from 512 bytes to 4096 bytes can provide
1184 better performance on most of the modern storage devices and
1185 also with some hw encryption accelerators.
1186 --persistent
1188 If used with LUKS2 devices and activation commands like open,
1189 the specified activation flags are persistently written into
1190 metadata and used next time automatically even for normal acti‐
1191 vation. (No need to use cryptab or other system configuration
1192 files.) Only --allow-discards, --perf-same_cpu_crypt,
1193 --perf-submit_from_crypt_cpus and --integrity-no-journal can be
1194 stored persistently.
1195 --refresh
1197 Refreshes an active device with new set of parameters. See
1198 action refresh description for more details.
1199 --label <LABEL>
1201 --subsystem <SUBSYSTEM> Set label and subsystem description for
1202 LUKS2 device, can be used in config and format actions. The
1203 label and subsystem are optional fields and can be later used in
1204 udev scripts for triggering user actions once device marked by
1205 these labels is detected.
1206 --integrity <integrity algorithm>
1208 Specify integrity algorithm to be used for authenticated disk
1209 encryption in LUKS2.
1210 WARNING: This extension is EXPERIMENTAL and requires dm-
1212 integrity kernel target (available since kernel version 4.12).
1213 For native AEAD modes, also enable "User-space interface for
1214 AEAD cipher algorithms" in "Cryptographic API" section (CON‐
1215 FIG_CRYPTO_USER_API_AEAD .config option).
1216 For more info, see AUTHENTICATED DISK ENCRYPTION section.
1218 --luks2-metadata-size <size>
1220 This option can be used to enlarge the LUKS2 metadata (JSON)
1221 area. The size includes 4096 bytes for binary metadata (usable
1222 JSON area is smaller of the binary area). According to LUKS2
1223 specification, only these values are valid: 16, 32, 64, 128,
1224 256, 512, 1024, 2048 and 4096 kB The <size> can be specified
1225 with unit suffix (for example 128k).
1226 --luks2-keyslots-size <size>
1228 This option can be used to set specific size of the LUKS2 binary
1229 keyslot area (key material is encrypted there). The value must
1230 be aligned to multiple of 4096 bytes with maximum size 128MB.
1231 The <size> can be specified with unit suffix (for example 128k).
1232 --keyslot-cipher <cipher-spec>
1234 This option can be used to set specific cipher encryption for
1235 the LUKS2 keyslot area.
1236 --keyslot-key-size <bits>
1238 This option can be used to set specific key size for the LUKS2
1239 keyslot area.
1240 --integrity-no-journal
1242 Activate device with integrity protection without using data
1243 journal (direct write of data and integrity tags). Note that
1244 without journal power fail can cause non-atomic write and data
1245 corruption. Use only if journalling is performed on a different
1246 storage layer.
1247 --integrity-no-wipe
1249 Skip wiping of device authentication (integrity) tags. If you
1250 skip this step, sectors will report invalid integrity tag until
1251 an application write to the sector.
1252 NOTE: Even some writes to the device can fail if the write is
1254 not aligned to page size and page-cache initiates read of a sec‐
1255 tor with invalid integrity tag.
1256 --unbound
1258 Creates new LUKS2 unbound keyslot. See luksAddKey action for
1260 more details.
1261 --tcrypt-hidden
1263 --tcrypt-system --tcrypt-backup Specify which TrueCrypt on-disk
1264 header will be used to open the device. See TCRYPT section for
1265 more info.
1266 --veracrypt
1268 Allow VeraCrypt compatible mode. Only for TCRYPT extension. See
1269 TCRYPT section for more info.
1270 --veracrypt-pim
1272 --veracrypt-query-pim Use a custom Personal Iteration Multiplier
1273 (PIM) for VeraCrypt device. See TCRYPT section for more info.
1274 --version
1276 Show the program version.
1277 --usage
1279 Show short option help.
1280 --help, -?
1282 Show help text and default parameters.
1283
1285 Cryptsetup returns 0 on success and a non-zero value on error.
1286 Error codes are: 1 wrong parameters, 2 no permission (bad passphrase),
1288 3 out of memory, 4 wrong device specified, 5 device already exists or
1289 device is busy.
1290
1292 Note that no iterated hashing or salting is done in plain mode. If
1293 hashing is done, it is a single direct hash. This means that low-
1294 entropy passphrases are easy to attack in plain mode.
1295 From a terminal: The passphrase is read until the first newline, i.e.
1297 '\n'. The input without the newline character is processed with the
1298 default hash or the hash specified with --hash. The hash result will
1299 be truncated to the key size of the used cipher, or the size specified
1300 with -s.
1301 From stdin: Reading will continue until a newline (or until the maximum
1303 input size is reached), with the trailing newline stripped. The maximum
1304 input size is defined by the same compiled-in default as for the maxi‐
1305 mum key file size and can be overwritten using --keyfile-size option.
1306 The data read will be hashed with the default hash or the hash speci‐
1308 fied with --hash. The hash result will be truncated to the key size of
1309 the used cipher, or the size specified with -s.
1310 Note that if --key-file=- is used for reading the key from stdin,
1312 trailing newlines are not stripped from the input.
1313 If "plain" is used as argument to --hash, the input data will not be
1315 hashed. Instead, it will be zero padded (if shorter than the key size)
1316 or truncated (if longer than the key size) and used directly as the
1317 binary key. This is useful for directly specifying a binary key. No
1318 warning will be given if the amount of data read from stdin is less
1319 than the key size.
1320 From a key file: It will be truncated to the key size of the used
1322 cipher or the size given by -s and directly used as a binary key.
1323 WARNING: The --hash argument is being ignored. The --hash option is
1325 usable only for stdin input in plain mode.
1326 If the key file is shorter than the key, cryptsetup will quit with an
1328 error. The maximum input size is defined by the same compiled-in
1329 default as for the maximum key file size and can be overwritten using
1330 --keyfile-size option.
1331
1335 LUKS uses PBKDF2 to protect against dictionary attacks and to give some
1336 protection to low-entropy passphrases (see RFC 2898 and the cryptsetup
1337 FAQ).
1338 From a terminal: The passphrase is read until the first newline and
1340 then processed by PBKDF2 without the newline character.
1341 From stdin: LUKS will read passphrases from stdin up to the first new‐
1343 line character or the compiled-in maximum key file length. If --key‐
1344 file-size is given, it is ignored.
1345 From key file: The complete keyfile is read up to the compiled-in maxi‐
1347 mum size. Newline characters do not terminate the input. The --key‐
1348 file-size option can be used to limit what is read.
1349 Passphrase processing: Whenever a passphrase is added to a LUKS header
1351 (luksAddKey, luksFormat), the user may specify how much the time the
1352 passphrase processing should consume. The time is used to determine the
1353 iteration count for PBKDF2 and higher times will offer better protec‐
1354 tion for low-entropy passphrases, but open will take longer to com‐
1355 plete. For passphrases that have entropy higher than the used key
1356 length, higher iteration times will not increase security.
1357 The default setting of one or two seconds is sufficient for most prac‐
1359 tical cases. The only exception is a low-entropy passphrase used on a
1360 device with a slow CPU, as this will result in a low iteration count.
1361 On a slow device, it may be advisable to increase the iteration time
1362 using the --iter-time option in order to obtain a higher iteration
1363 count. This does slow down all later luksOpen operations accordingly.
1364
1366 LUKS checks for a valid passphrase when an encrypted partition is
1367 unlocked. The behavior of plain dm-crypt is different. It will always
1368 decrypt with the passphrase given. If the given passphrase is wrong,
1369 the device mapped by plain dm-crypt will essentially still contain
1370 encrypted data and will be unreadable.
1371
1373 The available combinations of ciphers, modes, hashes and key sizes
1374 depend on kernel support. See /proc/crypto for a list of available
1375 options. You might need to load additional kernel crypto modules in
1376 order to get more options.
1377 For the --hash option, if the crypto backend is libgcrypt, then all
1379 algorithms supported by the gcrypt library are available. For other
1380 crypto backends, some algorithms may be missing.
1381
1383 Mathematics can't be bribed. Make sure you keep your passphrases safe.
1384 There are a few nice tricks for constructing a fallback, when suddenly
1385 out of the blue, your brain refuses to cooperate. These fallbacks need
1386 LUKS, as it's only possible with LUKS to have multiple passphrases.
1387 Still, if your attacker model does not prevent it, storing your
1388 passphrase in a sealed envelope somewhere may be a good idea as well.
1389
1391 Random Number Generators (RNG) used in cryptsetup are always the kernel
1392 RNGs without any modifications or additions to data stream produced.
1393 There are two types of randomness cryptsetup/LUKS needs. One type
1395 (which always uses /dev/urandom) is used for salts, the AF splitter and
1396 for wiping deleted keyslots.
1397 The second type is used for the volume (master) key. You can switch
1399 between using /dev/random and /dev/urandom here, see --use-random and
1400 --use-urandom options. Using /dev/random on a system without enough
1401 entropy sources can cause luksFormat to block until the requested
1402 amount of random data is gathered. In a low-entropy situation (embedded
1403 system), this can take a very long time and potentially forever. At the
1404 same time, using /dev/urandom in a low-entropy situation will produce
1405 low-quality keys. This is a serious problem, but solving it is out of
1406 scope for a mere man-page. See urandom(4) for more information.
1407
1409 Since Linux kernel version 4.12 dm-crypt supports authenticated disk
1410 encryption.
1411 Normal disk encryption modes are length-preserving (plaintext sector is
1413 of the same size as a ciphertext sector) and can provide only confiden‐
1414 tiality protection, but not cryptographically sound data integrity pro‐
1415 tection.
1416 Authenticated modes require additional space per-sector for authentica‐
1418 tion tag and use Authenticated Encryption with Additional Data (AEAD)
1419 algorithms.
1420 If you configure LUKS2 device with data integrity protection, there
1422 will be an underlying dm-integrity device, which provides additional
1423 per-sector metadata space and also provide data journal protection to
1424 ensure atomicity of data and metadata update. Because there must be
1425 additional space for metadata and journal, the available space for the
1426 device will be smaller than for length-preserving modes.
1427 The dm-crypt device then resides on top of such a dm-integrity device.
1429 All activation and deactivation of this device stack is performed by
1430 cryptsetup, there is no difference in using luksOpen for integrity pro‐
1431 tected devices. If you want to format LUKS2 device with data integrity
1432 protection, use --integrity option.
1433 Some integrity modes requires two independent keys (key for encryption
1435 and for authentication). Both these keys are stored in one LUKS
1436 keyslot.
1437 WARNING: All support for authenticated modes is experimental and there
1439 are only some modes available for now. Note that there are a very few
1440 authenticated encryption algorithms that are suitable for disk encryp‐
1441 tion.
1442
1445 Cryptsetup is usually used directly on a block device (disk partition
1446 or LVM volume). However, if the device argument is a file, cryptsetup
1447 tries to allocate a loopback device and map it into this file. This
1448 mode requires Linux kernel 2.6.25 or more recent which supports the
1449 loop autoclear flag (loop device is cleared on the last close automati‐
1450 cally). Of course, you can always map a file to a loop-device manually.
1451 See the cryptsetup FAQ for an example.
1452 When device mapping is active, you can see the loop backing file in the
1454 status command output. Also see losetup(8).
1455
1457 The LUKS2 on-disk metadata is updated in several steps and to achieve
1458 proper atomic update, there is a locking mechanism. For an image in
1459 file, code uses flock(2) system call. For a block device, lock is per‐
1460 formed over a special file stored in a locking directory (by default
1461 /run/lock/cryptsetup). The locking directory should be created with
1462 the proper security context by the distribution during the boot-up
1463 phase. Only LUKS2 uses locks, other formats do not use this mechanism.
1464
1466 The reload action is no longer supported. Please use dmsetup(8) if you
1467 need to directly manipulate with the device mapping table.
1468 The luksDelKey was replaced with luksKillSlot.
1470
1472 Report bugs, including ones in the documentation, on the cryptsetup
1473 mailing list at <dm-crypt@saout.de> or in the 'Issues' section on LUKS
1474 website. Please attach the output of the failed command with the
1475 --debug option added.
1476
1478 cryptsetup originally written by Jana Saout <jana@saout.de>
1479 The LUKS extensions and original man page were written by Clemens Fruh‐
1480 wirth <clemens@endorphin.org>.
1481 Man page extensions by Milan Broz <gmazyland@gmail.com>.
1482 Man page rewrite and extension by Arno Wagner <arno@wagner.name>.
1483
1485 Copyright © 2004 Jana Saout
1486 Copyright © 2004-2006 Clemens Fruhwirth
1487 Copyright © 2012-2014 Arno Wagner
1488 Copyright © 2009-2019 Red Hat, Inc.
1489 Copyright © 2009-2019 Milan Broz
1490 This is free software; see the source for copying conditions. There is
1492 NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
1493 PURPOSE.
1494
1496 The LUKS website at https://gitlab.com/cryptsetup/cryptsetup/
1497 The cryptsetup FAQ, contained in the distribution package and online at
1499 https://gitlab.com/cryptsetup/cryptsetup/wikis/FrequentlyAskedQuestions
1500 The cryptsetup mailing list and list archive, see FAQ entry 1.6.
1502 The LUKS on-disk format specification available at https://git‐
1504 lab.com/cryptsetup/cryptsetup/wikis/Specification
1505cryptsetup January 2019 CRYPTSETUP(8)