1 .TH CRYPTSETUP "8" "" "cryptsetup" "Maintenance Commands"
3 cryptsetup - setup cryptographic volumes for dm-crypt (including LUKS extension)
5 .B cryptsetup <options> <action> <action args>
8 cryptsetup is used to conveniently setup dm-crypt managed device-mapper mappings.
10 For basic (plain) dm-crypt mappings, there are four operations.
12 \fIcreate\fR <name> <device>
14 creates a mapping with <name> backed by device <device>.
16 \fB<options>\fR can be [\-\-hash, \-\-cipher, \-\-verify-passphrase,
17 \-\-key-file, \-\-keyfile-offset, \-\-key-size, \-\-offset, \-\-skip, \-\-size,
18 \-\-readonly, \-\-shared, \-\-allow-discards]
22 removes an existing mapping <name>.
26 reports the status for the mapping <name>.
30 resizes an active mapping <name>.
32 If \-\-size (in sectors) is not specified, the size of the underlying block device is used.
34 LUKS, Linux Unified Key Setup, is a standard for hard disk encryption.
35 It standardizes a partition header as well as the format of the bulk data.
36 LUKS can manage multiple passwords that can be individually revoked and
37 effectively scrubbed from persistent media, and that are protected
38 against dictionary attacks with PBKDF2.
40 Each password, usually called a
42 in this document, is associated with a slot, of which there are typically 8.
43 Key operations that do not specify a slot affect the first slot
44 matching the supplied key.
46 These are valid LUKS actions:
48 \fIluksFormat\fR <device> [<key file>]
50 initializes a LUKS partition and sets the initial key, either via prompting or via <key file>.
52 \fB<options>\fR can be [\-\-cipher, \-\-verify-passphrase, \-\-key-size,
53 \-\-key-slot, \-\-key-file (takes precedence over optional second argument),
54 \-\-keyfile-offset, \-\-keyfile-size, \-\-use-random | \-\-use-urandom, \-\-uuid,
57 \fIluksOpen\fR <device> <name>
59 opens the LUKS partition <device> and sets up a mapping <name> after
60 successful verification of the supplied key material
61 (either via key file by \-\-key-file, or via prompting).
63 Device parameter can be also specified by LUKS UUID in the format UUID=<uuid>
64 (then cryptsetup will use /dev/disk/by-uuid symlinks).
66 \fB<options>\fR can be [\-\-key-file, \-\-keyfile-offset, \-\-keyfile-size, \-\-readonly,
67 \-\-allow-discards, \-\-header, \-\-key-slot, \-\-master-key-file].
69 \fIluksClose\fR <name>
71 identical to \fIremove\fR.
73 \fIluksSuspend\fR <name>
75 suspends active device (all IO operations are frozen) and wipes encryption
76 key from kernel. Kernel version 2.6.19 or later is required.
78 After that operation you have to use \fIluksResume\fR to reinstate
79 encryption key (and resume device) or \fIluksClose\fR to remove mapped device.
81 \fBWARNING:\fR never try to suspend device where is the cryptsetup binary itself.
83 \fB<options>\fR can be [\-\-header].
85 \fIluksResume\fR <name>
87 Resumes suspended device and reinstates encryption key. You will need provide passphrase
88 identical to \fIluksOpen\fR command (using prompting or key file).
90 \fB<options>\fR can be [\-\-key-file, \-\-keyfile-size, \-\-header]
92 \fIluksAddKey\fR <device> [<new key file>]
94 add a new key file/passphrase. An existing passphrase or key file
95 (via \-\-key-file) must be supplied.
96 The key file with the new material is supplied as a positional argument.
98 \fB<options>\fR can be [\-\-key-file, \-\-keyfile-offset, \-\-keyfile-size, \-\-new-keyfile-offset,
99 \-\-new-keyfile-size, \-\-key-slot, \-\-master-key-file].
101 \fIluksRemoveKey\fR <device> [<key file>]
103 remove supplied key or key file from LUKS device in the manner of \fIluksKillSlot\fR.
105 \fIluksChangeKey\fR <device> [<new key file>]
107 change existing key file or passphrase. An existing passphrase
108 or key file (via \-\-key-file) must be supplied.
109 The key file with the new material is supplied as a positional argument.
111 If no key slot is specified (and there is still free key slot on device)
112 new slot is allocated before the old is purged.
114 If \fB\-\-key\-slot\fR option is specified (or there is no free slot)
115 command will overwrite existing slot.
117 \fBWARNING:\fR Be sure you have another slot active or header backup
118 when using explicit key slot (so you can unlock the device even after
119 possible media failure during slot swap).
121 \fB<options>\fR can be [\-\-key-file, \-\-keyfile-offset, \-\-keyfile-size, \-\-new-keyfile-offset,
122 \-\-new-keyfile-size, \-\-key-slot].
124 \fIluksKillSlot\fR <device> <key slot number>
126 wipe key with number <key slot> from LUKS device. A remaining passphrase or
127 key file (via \-\-key-file) must be supplied.
129 \fB<options>\fR can be [\-\-key-file, \-\-keyfile-offset, \-\-keyfile-size].
131 \fIluksUUID\fR <device>
133 print UUID, if <device> has a LUKS header.
135 set new UUID if \fI\-\-uuid\fR option is specified.
137 \fIisLuks\fR <device>
139 returns true, if <device> is a LUKS partition. Otherwise, false.
141 \fIluksDump\fR <device>
143 dumps the header information of a LUKS partition.
145 If \-\-dump-master-key option is used, the volume (master) key is dumped
146 instead of keyslot info.
148 Because this information can be used to access encrypted device without
149 passphrase knowledge (even without LUKS header) use this option
152 Dump with volume key (either printed or stored to file) should be always
153 stored encrypted and on safe place.
155 LUKS passphrase or key file is required for volume key dump.
157 \fB<options>\fR can be [\-\-dump-master-key, \-\-key-file, \-\-keyfile-offset, \-\-keyfile-size].
159 \fIluksHeaderBackup\fR <device> \-\-header-backup-file <file>
161 Stores binary backup of LUKS header and keyslot areas.
163 \fBWARNING:\fR Please note that with this backup file (and old passphrase
164 knowledge) you can decrypt data even if old passphrase was wiped from real device.
166 Also note that anti-forensic splitter is not used during manipulation with backup file.
168 \fIluksHeaderRestore\fR <device> \-\-header-backup-file <file>
170 Restores binary backup of LUKS header and keyslot areas from specified file.
172 \fBWARNING:\fR All the keyslot areas are overwritten, only active keyslots
173 form backup file are available after issuing this command.
175 This command allows restoring header if device do not contain LUKS header
176 or if the master key size and data offset in LUKS header on device match the backup file.
178 \fIrepair\fR <device>
180 Tries to repair (LUKS) device metadata if possible.
182 This command is useful to fix known benign LUKS metadata header corruptions.
183 Only basic corruptions of unused keyslot are fixable, any rewrite
184 of keyslot data or used keyslot or header metadata means lost of device.
186 \fBWARNING:\fR Always store binary copy of the original header, for
187 LUKS, \fIrepair\fR will not touch more than 4kB from the start of device
188 (visible LUKS header).
190 For more information about LUKS, see
191 \fBhttp://code.google.com/p/cryptsetup/wiki/Specification\fR
192 .SH loop-AES EXTENSION
193 cryptsetup supports mapping of loop-AES encrypted partition using
194 compatible dm-crypt mode.
196 \fIloopaesOpen\fR <device> <name> \-\-key-file <keyfile>
198 opens the loop-AES <device> and sets up a mapping <name>.
200 N.B. If key file is in GPG encrypted format, you have to use
201 \-\-key-file=- and decrypt it before use.
202 gpg \-\-decrypt <keyfile> | cryptsetup loopaesOpen \-\-key-file=- <device> <name>
204 Use \fB\-\-key-file\fR to specify proper key length, default compiled-in
205 parameters are visible in \fB\-\-help\fR output.
207 Use \fB\-\-offset\fR to specify device offset. Note the units need to be
208 specified in 512 bytes sectors.
210 Use \fB\-\-skip\fR to specify IV offset. If original device used offset
211 and not used it in IV sector calculations, you have to explicitly use
212 \fB\-\-skip 0\fR in addition to offset parameter.
214 Use \fB\-\-hash\fR to override hash function for password hashing
215 (otherwise it is detected according to key size).
217 \fB<options>\fR can be [\-\-key-file, \-\-key-size, \-\-offset, \-\-skip,
218 \-\-hash, \-\-readonly, \-\-allow-discards].
220 \fIloopaesClose\fR <name>
222 identical to \fIremove\fR.
224 For more information about loop-AES, see \fBhttp://loop-aes.sourceforge.net\fR
227 .B "\-\-verbose, \-v"
228 Print more verbose messages.
231 Run in debug mode with full diagnostic logs.
234 For \fIcreate\fR and \fIloopaesOpen\fR action specifies hash to use for password hashing.
236 For \fIluksFormat\fR action specifies hash used in LUKS key setup scheme
237 and volume key digest.
239 \fBWARNING:\fR setting hash other than \fBsha1\fR causes LUKS device
240 incompatible with older version of cryptsetup.
242 The hash string is passed to libgcrypt, so all hash algorithms are supported
243 (for \fIluksFormat\fR algorithm must provide at least 20 byte long hash).
244 Default is set during compilation, compatible values with old version of cryptsetup are
245 \fB"ripemd160"\fR for \fIcreate\fR action and \fB"sha1"\fR for \fIluksFormat\fR.
247 Use \fIcryptsetup \-\-help\fR to show defaults.
250 set cipher specification string.
252 Default mode is configurable during compilation,
253 you can see compiled-in default using \fIcryptsetup \-\-help\fR.
254 If not changed, the default is for plain dm-crypt and LUKS mappings
255 "aes-cbc-essiv:sha256".
257 For XTS mode, kernel version 2.6.24 or more recent is required.
258 Use "aes-xts-plain64" cipher specification and set key size to 256
259 (or 512) bits (see \-s option).
260 Note that plain64 IV (Initialization Vector) is available since kernel version 2.6.33
261 and it is full 64bit version of plain IV. For more info please see FAQ.
263 .B "\-\-verify-passphrase, \-y"
264 query for passwords twice. Useful when creating a (regular) mapping
265 for the first time, or when running \fIluksFormat\fR.
267 Password verification option is ignored if requested on non terminal
268 input (like pipe of file).
270 .B "\-\-key-file, \-d"
271 use file as key material.
273 With LUKS, key material supplied in key files via \-d are always used
274 for existing passphrases, except in \fIluksFormat\fR action where
275 \-d is equivalent to positional key file argument.
277 If you want to set a new key via a key file, you have to use
278 a positional arg to \fIluksAddKey\fR.
280 If the key file is "-", stdin will be used. With the "-" key file
281 reading will not stop when new line character is detected.
283 See section \fBNOTES ON PASSWORD PROCESSING\fR for more information.
285 .B "\-\-keyfile-offset \fIvalue\fR"
286 Begins read from key file at \fIvalue\fR bytes.
287 Usable together with all commands using key file.
289 .B "\-\-keyfile-size, \-l \fIvalue\fR"
290 Limits read from key file to \fIvalue\fR bytes.
291 Usable together with all commands using key file.
293 .B "\-\-new-keyfile-offset \fIvalue\fR"
294 Begins read from new key file at \fIvalue\fR bytes in \fIluksAddKey\fR when
295 adding new key file. Default is to start at the beginning of key file.
297 .B "\-\-new-keyfile-size \fIvalue\fR"
298 Limits read from new key file to \fIvalue\fR bytes in \fIluksAddKey\fR when
299 adding new key file. Default is exhaustive read from key file.
301 .B "\-\-master-key-file"
302 Use pre-generated master key stored in file. For \fIluksFormat\fR it allows
303 LUKS header reformatting with the same master key (if all other parameters
304 are the same existing encrypted data remains intact).
306 For \fIluksAddKey\fR it allows adding new passphrase with only master key knowledge.
308 For \fIluksOpen\fR it allows to open the LUKS device with only master key knowledge.
311 .B "\-\-dump-master-key"
312 For \fIluksDump\fR it allows LUKS header dump including volume (master) key.
313 Use with care (this information allows access to device without passphrase knowledge).
315 See \fIluksDump\fR for more info.
320 For \fIluksFormat\fR it defines which kernel random number generator will
321 be used for long-term key (volume key).
323 See \fBNOTES ON RNG\fR for more information. Use \fIcryptsetup \-\-help\fR
326 .B "\-\-key-slot, \-S"
327 For LUKS operations that add key material, this options allows you
328 to specify which key slot is selected for the new key.
329 This option can be used for \fIluksFormat\fR, \fIluksOpen\fR and \fIluksAddKey\fR.
331 .B "\-\-key-size, \-s"
332 set key size in bits.
334 Has to be a multiple of 8 bits. The key size is limited by the used cipher.
336 See output of /proc/crypto for more information.
338 Can be used for \fIcreate\fR or \fIluksFormat\fR, all other LUKS actions
339 will use key-size specified by the LUKS header.
340 Default is set during compilation, if not changed it is 256 bits.
342 Use \fIcryptsetup \-\-help\fR to show defaults.
345 force the size of the underlying device in sectors.
346 This option is only relevant for \fIcreate\fR and \fIresize\fR action.
349 start offset in the backend device (in 512-byte sectors).
350 This option is only relevant for \fIcreate\fR and \fIloopaesOpen\fR action.
353 how many sectors of the encrypted data to skip at the beginning.
354 This is different from the \-\-offset options with respect to IV calculations.
355 Using \-\-offset will shift the IV calculation by the same negative amount.
356 Hence, if \-\-offset \fIn\fR, sector \fIn\fR will be the first sector
357 on the mapping with IV \fI0\fR. Using \-\-skip would have resulted in sector
358 \fIn\fR being the first sector also, but with IV \fIn\fR.
359 This option is only relevant for \fIcreate\fR and \fIloopaesOpen\fR action.
362 set up a read-only mapping.
365 create another non-overlapping mapping to one common ciphertext device,
366 e.g. to create hidden device inside another encrypted device.
367 This option is only relevant for \fIcreate\fR action.
368 Use \-\-offset, \-\-size and \-\-skip to specify mapped area.
370 .B "\-\-iter-time, \-i"
371 The number of milliseconds to spend with PBKDF2 password processing.
372 This option is only relevant to the LUKS operations as
373 \fIluksFormat\fR or \fIluksAddKey\fR.
374 Note that 0 means default.
376 .B "\-\-batch-mode, \-q"
377 Do not ask for confirmation. Use with care!
379 If \-y option is not specified, batch mode option also switches off
380 passphrase verification for \fIluksFormat\fR.
382 .B "\-\-timeout, \-t"
383 The number of seconds to wait before timeout. This option is relevant every
384 time a password is asked, like \fIcreate\fR, \fIluksOpen\fR, \fIluksFormat\fR
385 or \fIluksAddKey\fR. It has no effect if used in conjunction with \-\-key-file.
388 How often the input of the passphrase shall be retried. This option is relevant
389 every time a password is asked, like \fIcreate\fR, \fIluksOpen\fR, \fIluksFormat\fR
390 or \fIluksAddKey\fR. The default is 3 tries.
392 .B "\-\-align-payload=\fIvalue\fR"
393 Align payload at a boundary of \fIvalue\fR 512-byte sectors.
394 This option is relevant for \fIluksFormat\fR.
396 If not specified, cryptsetup tries to use topology info provided by kernel
397 for underlying device to get optimal alignment.
398 If not available (or calculated value is multiple of default) data is by
399 default aligned to 1 MiB boundary (2048 512-byte sectors).
401 For detached LUKS header it specifies offset on data device.
402 See also \-\-header option.
404 .B "\-\-uuid=\fIUUID\fR"
405 Use provided \fIUUID\fR in \fIluksFormat\fR command instead of generating
406 new one or change existing UUID in \fIluksUUID\fR command.
408 The UUID must be provided in standard UUID format
409 (e.g. 12345678-1234-1234-1234-123456789abc).
411 .B "\-\-allow-discards\fR"
412 Allow using of discards (TRIM) requests for device.
413 This option is only relevant for \fIcreate\fR, \fIluksOpen\fR or \fIloopaesOpen\fR.
415 \fBWARNING:\fR Assess the specific security risks carefully before enabling this
416 option. For example, allowing discards on encrypted devices may lead to the leak
417 of information about the ciphertext device (filesystem type, used space etc.)
418 if the discarded blocks can be located easily on the device later.
420 Kernel version 3.1 or more recent is required.
421 For older versions is the option ignored.
424 Set detached (separated) metadata device or file with LUKS header.
426 This options allows separation of ciphertext device and on-disk metadata header.
428 This option is only relevant for LUKS devices and can be used in \fIluksFormat\fR,
429 \fIluksOpen\fR, \fIluksSuspend\fR, \fIluksResume\fR, \fIstatus\fR and
430 \fIresize\fR commands.
432 If used with \fIluksFormat\fR the \-\-align-payload option is taken
433 as absolute sector alignment on ciphertext device and can be zero.
435 For other commands with separated metadata device you have to always specify
436 path to metadata device (not to the ciphertext device).
438 \fBWARNING:\fR There is no possible check that specified ciphertext device
439 is correct if on-disk header is detached. Use with care.
444 Crypsetup returns 0 on success or non-zero on error.
446 Error codes are: 1 wrong parameters, 2 no permission (bad passphrase),
447 3 out of memory, 4 wrong device specified, 5 device already exists
449 .SH NOTES ON PASSWORD PROCESSING FOR PLAIN MODE
450 \fBFrom a terminal\fR: Password processing is new-line sensitive,
451 meaning the reading will stop after encountering \\n.
452 It will process the read material (without newline) with the default
453 hash or the hash given by \-\-hash.
454 After hashing, it will be cropped to the key size given by \-s.
456 \fBFrom stdin\fR: Reading will continue until EOF (or until
457 maximum input size is reached), with the trailing newline stripped.
458 The maximum input size is defined by the same compiled-in default
459 as for the maximum key file size or can be overwrittten
460 using \-\-keysfile-size option.
462 After that the read data will be hashed with the default hash
463 or the hash given by \-\-hash and the result will be cropped
464 to the keysize given by \-s.
466 If "plain" is used as an argument to the hash option, the input
467 data will not be hashed.
468 Instead, it will be zero padded (if shorter than the keysize) or
469 truncated (if longer than the keysize) and used directly as the key.
470 No warning will be given if the amount of data read from stdin is
471 less than the keysize.
473 \fBFrom a key file\fR: It will be cropped to the size given by \-s.
474 If there is insufficient key material in the key file, cryptsetup
475 will quit with an error.
477 If \-\-key-file=- is used for reading the key from stdin, no
478 trailing newline is stripped from the input. Without that option,
479 cryptsetup strips trailing newlines from stdin input.
480 .SH NOTES ON PASSWORD PROCESSING FOR LUKS
481 LUKS uses PBKDF2 to protect against dictionary attacks (see RFC 2898).
483 LUKS will always do an exhaustive password reading.
484 Hence, password can not be read from /dev/random, /dev/zero or any
485 other stream that does not terminate.
486 To prevent exhausting of system memory, cryptsetup limits
487 maximum key file size. Compiled-in default is displayed in \-\-help
488 output. You can limit reads from key file using \-\-key-size option,
489 this option takes precedence over compiled-in default.
491 For any password creation action (luksAddKey, or luksFormat),
492 the user may specify how much the time the password processing
493 should consume. Increasing the time will lead to a more secure
494 password, but also will take luksOpen longer to complete.
495 The default setting of one second is sufficient for good security.
496 .SH INCOHERENT BEHAVIOUR FOR INVALID PASSWORDS/KEYS
497 LUKS checks for a valid password or key when an encrypted partition
498 is unlocked. Thus the luksOpen action fails with invalid password
499 or key, contrary to the plain dm-crypt create action.
501 Please also be sure that you are using the same keyboard and
502 language setting as during device format.
503 .SH NOTES ON SUPPORTED CIPHERS, MODES, HASHES AND KEY SIZES
504 The available combinations of ciphers, modes, hashes and key sizes
505 depend on kernel support. See /proc/crypto for a list of available
506 options. You might need to load additional kernel crypto modules
507 in order to get more options.
509 For \-\-hash option all algorithms supported by gcrypt library are available.
510 .SH NOTES ON PASSWORDS
511 Mathematics can't be bribed. Make sure you keep your passwords safe.
512 There are a few nice tricks for constructing a fallback, when suddenly
513 out of (or after being) blue, your brain refuses to cooperate.
514 These fallbacks are possible with LUKS, as it's only possible with LUKS
515 to have multiple passwords.
517 Random Number Generator (RNG) used in cryptsetup always uses kernel RNG without
518 any modifications or additions to data stream procudes by kernel (like internal
519 random pool operations or mixing with the other random sources).
521 There are two types of randomness cryptsetup/LUKS needs. One type (which always
522 uses /dev/urandom) is used for salt, AF splitter and for wiping removed
525 Second type is used for volume (master) key. You can switch between
526 using /dev/random and /dev/urandom here, see \fP\-\-use-random\fR and \fP\-\-use-urandom\fR
527 options. Using /dev/random on system without enough entropy sources
528 can cause \fPluksFormat\fR to block until the requested amount of random data is gathered.
529 See \fPurandom(4)\fR for more information.
530 .SH NOTES ON LOOPBACK DEVICE USE
531 Cryptsetup is usually used directly over block device (like disk partition or LVM volume).
532 However if the device argument is file, cryptsetup tries to allocate loopback device
533 and map it into this file. This mode requires Linux kernel 2.6.25 or more recent which
534 supports loop autoclear flag (loop device is cleared on last close automatically).
536 When device mapping is active, you can see loop backing file in status command output.
539 cryptsetup is written by Christophe Saout <christophe@saout.de>
541 LUKS extensions, and man page by Clemens Fruhwirth <clemens@endorphin.org>
542 .SH DEPRECATED ACTIONS
544 The \fIreload\fR action is no longer supported.
545 Please use \fIdmsetup(8)\fR if you need to
546 directly manipulate with the device mapping table.
548 The \fIluksDelKey\fR was replaced with \fIluksKillSlot\fR.
551 Report bugs to <dm-crypt@saout.de> or Issues section on LUKS website.
552 Please attach output of failed command with added \-\-debug option.
554 Copyright \(co 2004 Christophe Saout
556 Copyright \(co 2004-2006 Clemens Fruhwirth
558 Copyright \(co 2009-2011 Red Hat, Inc.
560 This is free software; see the source for copying conditions. There is NO
561 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
563 LUKS website, \fBhttp://code.google.com/p/cryptsetup/\fR