1CRYPTTAB(5) crypttab CRYPTTAB(5)
2
6 crypttab - Configuration for encrypted block devices
7
9 /etc/crypttab
10
12 The /etc/crypttab file describes encrypted block devices that are set
13 up during system boot.
14 Empty lines and lines starting with the "#" character are ignored. Each
16 of the remaining lines describes one encrypted block device. Fields are
17 delimited by white space.
18 Each line is in the form
20 volume-name encrypted-device key-file options
22 The first two fields are mandatory, the remaining two are optional.
24 Setting up encrypted block devices using this file supports four
26 encryption modes: LUKS, TrueCrypt, BitLocker and plain. See
27 cryptsetup(8) for more information about each mode. When no mode is
28 specified in the options field and the block device contains a LUKS
29 signature, it is opened as a LUKS device; otherwise, it is assumed to
30 be in raw dm-crypt (plain mode) format.
31 The four fields of /etc/crypttab are defined as follows:
33 1. The first field contains the name of the resulting volume with
35 decrypted data; its block device is set up below /dev/mapper/.
36 2. The second field contains a path to the underlying block device or
38 file, or a specification of a block device via "UUID=" followed by
39 the UUID.
40 3. The third field specifies an absolute path to a file with the
42 encryption key. Optionally, the path may be followed by ":" and an
43 /etc/fstab style device specification (e.g. starting with "LABEL="
44 or similar); in which case the path is taken relative to the
45 specified device's file system root. If the field is not present or
46 is "none" or "-", a key file named after the volume to unlock (i.e.
47 the first column of the line), suffixed with .key is automatically
48 loaded from the /etc/cryptsetup-keys.d/ and /run/cryptsetup-keys.d/
49 directories, if present. Otherwise, the password has to be manually
50 entered during system boot. For swap encryption, /dev/urandom may
51 be used as key file, resulting in a randomized key.
52 If the specified key file path refers to an AF_UNIX stream socket
54 in the file system, the key is acquired by connecting to the socket
55 and reading it from the connection. This allows the implementation
56 of a service to provide key information dynamically, at the moment
57 when it is needed. For details see below.
58 4. The fourth field, if present, is a comma-delimited list of options.
60 The supported options are listed below.
61
63 Six different mechanisms for acquiring the decryption key or passphrase
64 unlocking the encrypted volume are supported. Specifically:
65 1. Most prominently, the user may be queried interactively during
67 volume activation (i.e. typically at boot), asking them to type in
68 the necessary passphrase(s).
69 2. The (unencrypted) key may be read from a file on disk, possibly on
71 removable media. The third field of each line encodes the location,
72 for details see above.
73 3. The (unencrypted) key may be requested from another service, by
75 specifying an AF_UNIX file system socket in place of a key file in
76 the third field. For details see above and below.
77 4. The key may be acquired via a PKCS#11 compatible hardware security
79 token or smartcard. In this case an encrypted key is stored on
80 disk/removable media, acquired via AF_UNIX, or stored in the LUKS2
81 JSON token metadata header. The encrypted key is then decrypted by
82 the PKCS#11 token with an RSA key stored on it, and then used to
83 unlock the encrypted volume. Use the pkcs11-uri= option described
84 below to use this mechanism.
85 5. Similar, the key may be acquired via a FIDO2 compatible hardware
87 security token (which must implement the "hmac-secret" extension).
88 In this case a (during enrollment) randomly generated key is stored
89 on disk/removable media, acquired via AF_UNIX, or stored in the
90 LUKS2 JSON token metadata header. The random key is hashed via a
91 keyed hash function (HMAC) on the FIDO2 token, using a secret key
92 stored on the token that never leaves it. The resulting hash value
93 is then used as key to unlock the encrypted volume. Use the
94 fido2-device= option described below to use this mechanism.
95 6. Similar, the key may be acquired via a TPM2 security chip. In this
97 case a (during enrollment) randomly generated key — encrypted by an
98 asymmetric key derived from the TPM2 chip's seed key — is stored on
99 disk/removable media, acquired via AF_UNIX, or stored in the LUKS2
100 JSON token metadata header. Use the tpm2-device= option described
101 below to use this mechanism.
102 For the latter five mechanisms the source for the key material used for
104 unlocking the volume is primarily configured in the third field of each
105 /etc/crypttab line, but may also configured in /etc/cryptsetup-keys.d/
106 and /run/cryptsetup-keys.d/ (see above) or in the LUKS2 JSON token
107 header (in case of the latter three). Use the systemd-cryptenroll(1)
108 tool to enroll PKCS#11, FIDO2 and TPM2 devices in LUKS2 volumes.
109
111 The following options may be used in the fourth field of each line:
112 cipher=
114 Specifies the cipher to use. See cryptsetup(8) for possible values
115 and the default value of this option. A cipher with unpredictable
116 IV values, such as "aes-cbc-essiv:sha256", is recommended. Embedded
117 commas in the cipher specification need to be escaped by preceding
118 them with a backslash, see example below.
119 discard
121 Allow discard requests to be passed through the encrypted block
122 device. This improves performance on SSD storage but has security
123 implications.
124 hash=
126 Specifies the hash to use for password hashing. See cryptsetup(8)
127 for possible values and the default value of this option.
128 header=
130 Use a detached (separated) metadata device or file where the LUKS
131 header is stored. This option is only relevant for LUKS devices.
132 See cryptsetup(8) for possible values and the default value of this
133 option.
134 Optionally, the path may be followed by ":" and an /etc/fstab
136 device specification (e.g. starting with "UUID=" or similar); in
137 which case, the path is relative to the device file system root.
138 The device gets mounted automatically for LUKS device activation
139 duration only.
140 keyfile-offset=
142 Specifies the number of bytes to skip at the start of the key file.
143 See cryptsetup(8) for possible values and the default value of this
144 option.
145 keyfile-size=
147 Specifies the maximum number of bytes to read from the key file.
148 See cryptsetup(8) for possible values and the default value of this
149 option. This option is ignored in plain encryption mode, as the key
150 file size is then given by the key size.
151 keyfile-erase
153 If enabled, the specified key file is erased after the volume is
154 activated or when activation fails. This is in particular useful
155 when the key file is only acquired transiently before activation
156 (e.g. via a file in /run/, generated by a service running before
157 activation), and shall be removed after use. Defaults to off.
158 key-slot=
160 Specifies the key slot to compare the passphrase or key against. If
161 the key slot does not match the given passphrase or key, but
162 another would, the setup of the device will fail regardless. This
163 option implies luks. See cryptsetup(8) for possible values. The
164 default is to try all key slots in sequential order.
165 keyfile-timeout=
167 Specifies the timeout for the device on which the key file resides
168 and falls back to a password if it could not be mounted. See
169 systemd-cryptsetup-generator(8) for key files on external devices.
170 luks
172 Force LUKS mode. When this mode is used, the following options are
173 ignored since they are provided by the LUKS header on the device:
174 cipher=, hash=, size=.
175 bitlk
177 Decrypt BitLocker drive. Encryption parameters are deduced by
178 cryptsetup from BitLocker header.
179 _netdev
181 Marks this cryptsetup device as requiring network. It will be
182 started after the network is available, similarly to
183 systemd.mount(5) units marked with _netdev. The service unit to set
184 up this device will be ordered between remote-fs-pre.target and
185 remote-cryptsetup.target, instead of cryptsetup-pre.target and
186 cryptsetup.target.
187 Hint: if this device is used for a mount point that is specified in
189 fstab(5), the _netdev option should also be used for the mount
190 point. Otherwise, a dependency loop might be created where the
191 mount point will be pulled in by local-fs.target, while the service
192 to configure the network is usually only started after the local
193 file system has been mounted.
194 noauto
196 This device will not be added to cryptsetup.target. This means that
197 it will not be automatically unlocked on boot, unless something
198 else pulls it in. In particular, if the device is used for a mount
199 point, it'll be unlocked automatically during boot, unless the
200 mount point itself is also disabled with noauto.
201 nofail
203 This device will not be a hard dependency of cryptsetup.target.
204 It'll still be pulled in and started, but the system will not wait
205 for the device to show up and be unlocked, and boot will not fail
206 if this is unsuccessful. Note that other units that depend on the
207 unlocked device may still fail. In particular, if the device is
208 used for a mount point, the mount point itself also needs to have
209 the nofail option, or the boot will fail if the device is not
210 unlocked successfully.
211 offset=
213 Start offset in the backend device, in 512-byte sectors. This
214 option is only relevant for plain devices.
215 plain
217 Force plain encryption mode.
218 read-only, readonly
220 Set up the encrypted block device in read-only mode.
221 same-cpu-crypt
223 Perform encryption using the same CPU that IO was submitted on. The
224 default is to use an unbound workqueue so that encryption work is
225 automatically balanced between available CPUs.
226 This requires kernel 4.0 or newer.
228 submit-from-crypt-cpus
230 Disable offloading writes to a separate thread after encryption.
231 There are some situations where offloading write requests from the
232 encryption threads to a dedicated thread degrades performance
233 significantly. The default is to offload write requests to a
234 dedicated thread because it benefits the CFQ scheduler to have
235 writes submitted using the same context.
236 This requires kernel 4.0 or newer.
238 no-read-workqueue
240 Bypass dm-crypt internal workqueue and process read requests
241 synchronously. The default is to queue these requests and process
242 them asynchronously.
243 This requires kernel 5.9 or newer.
245 no-write-workqueue
247 Bypass dm-crypt internal workqueue and process write requests
248 synchronously. The default is to queue these requests and process
249 them asynchronously.
250 This requires kernel 5.9 or newer.
252 skip=
254 How many 512-byte sectors of the encrypted data to skip at the
255 beginning. This is different from the offset= option with respect
256 to the sector numbers used in initialization vector (IV)
257 calculation. Using offset= will shift the IV calculation by the
258 same negative amount. Hence, if offset=n is given, sector n will
259 get a sector number of 0 for the IV calculation. Using skip= causes
260 sector n to also be the first sector of the mapped device, but with
261 its number for IV generation being n.
262 This option is only relevant for plain devices.
264 size=
266 Specifies the key size in bits. See cryptsetup(8) for possible
267 values and the default value of this option.
268 sector-size=
270 Specifies the sector size in bytes. See cryptsetup(8) for possible
271 values and the default value of this option.
272 swap
274 The encrypted block device will be used as a swap device, and will
275 be formatted accordingly after setting up the encrypted block
276 device, with mkswap(8). This option implies plain.
277 WARNING: Using the swap option will destroy the contents of the
279 named partition during every boot, so make sure the underlying
280 block device is specified correctly.
281 tcrypt
283 Use TrueCrypt encryption mode. When this mode is used, the
284 following options are ignored since they are provided by the
285 TrueCrypt header on the device or do not apply: cipher=, hash=,
286 keyfile-offset=, keyfile-size=, size=.
287 When this mode is used, the passphrase is read from the key file
289 given in the third field. Only the first line of this file is read,
290 excluding the new line character.
291 Note that the TrueCrypt format uses both passphrase and key files
293 to derive a password for the volume. Therefore, the passphrase and
294 all key files need to be provided. Use tcrypt-keyfile= to provide
295 the absolute path to all key files. When using an empty passphrase
296 in combination with one or more key files, use "/dev/null" as the
297 password file in the third field.
298 tcrypt-hidden
300 Use the hidden TrueCrypt volume. This option implies tcrypt.
301 This will map the hidden volume that is inside of the volume
303 provided in the second field. Please note that there is no
304 protection for the hidden volume if the outer volume is mounted
305 instead. See cryptsetup(8) for more information on this limitation.
306 tcrypt-keyfile=
308 Specifies the absolute path to a key file to use for a TrueCrypt
309 volume. This implies tcrypt and can be used more than once to
310 provide several key files.
311 See the entry for tcrypt on the behavior of the passphrase and key
313 files when using TrueCrypt encryption mode.
314 tcrypt-system
316 Use TrueCrypt in system encryption mode. This option implies
317 tcrypt.
318 tcrypt-veracrypt
320 Check for a VeraCrypt volume. VeraCrypt is a fork of TrueCrypt that
321 is mostly compatible, but uses different, stronger key derivation
322 algorithms that cannot be detected without this flag. Enabling this
323 option could substantially slow down unlocking, because VeraCrypt's
324 key derivation takes much longer than TrueCrypt's. This option
325 implies tcrypt.
326 timeout=
328 Specifies the timeout for querying for a password. If no unit is
329 specified, seconds is used. Supported units are s, ms, us, min, h,
330 d. A timeout of 0 waits indefinitely (which is the default).
331 tmp=
333 The encrypted block device will be prepared for using it as /tmp/;
334 it will be formatted using mkfs(8). Takes a file system type as
335 argument, such as "ext4", "xfs" or "btrfs". If no argument is
336 specified defaults to "ext4". This option implies plain.
337 WARNING: Using the tmp option will destroy the contents of the
339 named partition during every boot, so make sure the underlying
340 block device is specified correctly.
341 tries=
343 Specifies the maximum number of times the user is queried for a
344 password. The default is 3. If set to 0, the user is queried for a
345 password indefinitely.
346 headless=
348 Takes a boolean argument, defaults to false. If true, never query
349 interactively for the password/PIN. Useful for headless systems.
350 verify
352 If the encryption password is read from console, it has to be
353 entered twice to prevent typos.
354 password-echo=yes|no|masked
356 Controls whether to echo passwords or security token PINs that are
357 read from console. Takes a boolean or the special string "masked".
358 The default is password-echo=masked.
359 If enabled, the typed characters are echoed literally. If disabled,
361 the typed characters are not echoed in any form, the user will not
362 get feedback on their input. If set to "masked", an asterisk ("*")
363 is echoed for each character typed. Regardless of which mode is
364 chosen, if the user hits the tabulator key ("↹") at any time, or
365 the backspace key ("⌫") before any other data has been entered,
366 then echo is turned off.
367 pkcs11-uri=
369 Takes either the special value "auto" or an RFC7512 PKCS#11 URI[1]
370 pointing to a private RSA key which is used to decrypt the
371 encrypted key specified in the third column of the line. This is
372 useful for unlocking encrypted volumes through PKCS#11 compatible
373 security tokens or smartcards. See below for an example how to set
374 up this mechanism for unlocking a LUKS2 volume with a YubiKey
375 security token.
376 If specified as "auto" the volume must be of type LUKS2 and must
378 carry PKCS#11 security token metadata in its LUKS2 JSON token
379 section. In this mode the URI and the encrypted key are
380 automatically read from the LUKS2 JSON token header. Use systemd-
381 cryptenroll(1) as simple tool for enrolling PKCS#11 security tokens
382 or smartcards in a way compatible with "auto". In this mode the
383 third column of the line should remain empty (that is, specified as
384 "-").
385 The specified URI can refer directly to a private RSA key stored on
387 a token or alternatively just to a slot or token, in which case a
388 search for a suitable private RSA key will be performed. In this
389 case if multiple suitable objects are found the token is refused.
390 The encrypted key configured in the third column of the line is
391 passed as is (i.e. in binary form, unprocessed) to RSA decryption.
392 The resulting decrypted key is then Base64 encoded before it is
393 used to unlock the LUKS volume.
394 Use systemd-cryptenroll --pkcs11-token-uri=list to list all
396 suitable PKCS#11 security tokens currently plugged in, along with
397 their URIs.
398 Note that many newer security tokens that may be used as PKCS#11
400 security token typically also implement the newer and simpler FIDO2
401 standard. Consider using fido2-device= (described below) to enroll
402 it via FIDO2 instead. Note that a security token enrolled via
403 PKCS#11 cannot be used to unlock the volume via FIDO2, unless also
404 enrolled via FIDO2, and vice versa.
405 fido2-device=
407 Takes either the special value "auto" or the path to a "hidraw"
408 device node (e.g. /dev/hidraw1) referring to a FIDO2 security
409 token that implements the "hmac-secret" extension (most current
410 hardware security tokens do). See below for an example how to set
411 up this mechanism for unlocking an encrypted volume with a FIDO2
412 security token.
413 If specified as "auto" the FIDO2 token device is automatically
415 discovered, as it is plugged in.
416 FIDO2 volume unlocking requires a client ID hash (CID) to be
418 configured via fido2-cid= (see below) and a key to pass to the
419 security token's HMAC functionality (configured in the line's third
420 column) to operate. If not configured and the volume is of type
421 LUKS2, the CID and the key are read from LUKS2 JSON token metadata
422 instead. Use systemd-cryptenroll(1) as simple tool for enrolling
423 FIDO2 security tokens, compatible with this automatic mode, which
424 is only available for LUKS2 volumes.
425 Use systemd-cryptenroll --fido2-device=list to list all suitable
427 FIDO2 security tokens currently plugged in, along with their device
428 nodes.
429 This option implements the following mechanism: the configured key
431 is hashed via they HMAC keyed hash function the FIDO2 device
432 implements, keyed by a secret key embedded on the device. The
433 resulting hash value is Base64 encoded and used to unlock the LUKS2
434 volume. As it should not be possible to extract the secret from the
435 hardware token, it should not be possible to retrieve the hashed
436 key given the configured key — without possessing the hardware
437 token.
438 Note that many security tokens that implement FIDO2 also implement
440 PKCS#11, suitable for unlocking volumes via the pkcs11-uri= option
441 described above. Typically the newer, simpler FIDO2 standard is
442 preferable.
443 fido2-cid=
445 Takes a Base64 encoded FIDO2 client ID to use for the FIDO2 unlock
446 operation. If specified, but fido2-device= is not,
447 fido2-device=auto is implied. If fido2-device= is used but
448 fido2-cid= is not, the volume must be of LUKS2 type, and the CID is
449 read from the LUKS2 JSON token header. Use systemd-cryptenroll(1)
450 for enrolling a FIDO2 token in the LUKS2 header compatible with
451 this automatic mode.
452 fido2-rp=
454 Takes a string, configuring the FIDO2 Relying Party (rp) for the
455 FIDO2 unlock operation. If not specified "io.systemd.cryptsetup" is
456 used, except if the LUKS2 JSON token header contains a different
457 value. It should normally not be necessary to override this.
458 tpm2-device=
460 Takes either the special value "auto" or the path to a device node
461 (e.g. /dev/tpmrm0) referring to a TPM2 security chip. See below
462 for an example how to set up this mechanism for unlocking an
463 encrypted volume with a TPM2 chip.
464 Use tpm2-pcrs= (see below) to configure the set of TPM2 PCRs to
466 bind the volume unlocking to. Use systemd-cryptenroll(1) as simple
467 tool for enrolling TPM2 security chips in LUKS2 volumes.
468 If specified as "auto" the TPM2 device is automatically discovered.
470 Use systemd-cryptenroll --tpm2-device=list to list all suitable
471 TPM2 devices currently available, along with their device nodes.
472 This option implements the following mechanism: when enrolling a
474 TPM2 device via systemd-cryptenroll on a LUKS2 volume, a randomized
475 key unlocking the volume is generated on the host and loaded into
476 the TPM2 chip where it is encrypted with an asymmetric "primary"
477 key pair derived from the TPM2's internal "seed" key. Neither the
478 seed key nor the primary key are permitted to ever leave the TPM2
479 chip — however, the now encrypted randomized key may. It is saved
480 in the LUKS2 volume JSON token header. When unlocking the encrypted
481 volume, the primary key pair is generated on the TPM2 chip again
482 (which works as long as the chip's seed key is correctly maintained
483 by the TPM2 chip), which is then used to decrypt (on the TPM2 chip)
484 the encrypted key from the LUKS2 volume JSON token header saved
485 there during enrollment. The resulting decrypted key is then used
486 to unlock the volume. When the randomized key is encrypted the
487 current values of the selected PCRs (see below) are included in the
488 operation, so that different PCR state results in different
489 encrypted keys and the decrypted key can only be recovered if the
490 same PCR state is reproduced.
491 tpm2-pcrs=
493 Takes a "+" separated list of numeric TPM2 PCR (i.e. "Platform
494 Configuration Register") indexes to bind the TPM2 volume unlocking
495 to. This option is only useful when TPM2 enrollment metadata is not
496 available in the LUKS2 JSON token header already, the way
497 systemd-cryptenroll writes it there. If not used (and no metadata
498 in the LUKS2 JSON token header defines it), defaults to a list of a
499 single entry: PCR 7. Assign an empty string to encode a policy that
500 binds the key to no PCRs, making the key accessible to local
501 programs regardless of the current PCR state.
502 token-timeout=
504 Specifies how long to wait at most for configured security devices
505 (i.e. FIDO2, PKCS#11, TPM2) to show up. Takes a time value in
506 seconds (but other time units may be specified too, see
507 systemd.time(7) for supported formats). Defaults to 30s. Once the
508 specified timeout elapsed authentication via password is attempted.
509 Note that this timeout applies to waiting for the security device
510 to show up — it does not apply to the PIN prompt for the device
511 (should one be needed) or similar. Pass 0 to turn off the time-out
512 and wait forever.
513 try-empty-password=
515 Takes a boolean argument. If enabled, right before asking the user
516 for a password it is first attempted to unlock the volume with an
517 empty password. This is useful for systems that are initialized
518 with an encrypted volume with only an empty password set, which
519 shall be replaced with a suitable password during first boot, but
520 after activation.
521 x-systemd.device-timeout=
523 Specifies how long systemd should wait for a block device to show
524 up before giving up on the entry. The argument is a time in seconds
525 or explicitly specified units of "s", "min", "h", "ms".
526 x-initrd.attach
528 Setup this encrypted block device in the initramfs, similarly to
529 systemd.mount(5) units marked with x-initrd.mount.
530 Although it's not necessary to mark the mount entry for the root
532 file system with x-initrd.mount, x-initrd.attach is still
533 recommended with the encrypted block device containing the root
534 file system as otherwise systemd will attempt to detach the device
535 during the regular system shutdown while it's still in use. With
536 this option the device will still be detached but later after the
537 root file system is unmounted.
538 All other encrypted block devices that contain file systems mounted
540 in the initramfs should use this option.
541 At early boot and when the system manager configuration is reloaded,
543 this file is translated into native systemd units by systemd-
544 cryptsetup-generator(8).
545
547 If the key file path (as specified in the third column of /etc/crypttab
548 entries, see above) refers to an AF_UNIX stream socket in the file
549 system, the key is acquired by connecting to the socket and reading the
550 key from the connection. The connection is made from an AF_UNIX socket
551 name in the abstract namespace, see unix(7) for details. The source
552 socket name is chosen according the following format:
553 NUL RANDOM "/cryptsetup/" VOLUME
555 In other words: a NUL byte (as required for abstract namespace
557 sockets), followed by a random string (consisting of alphanumeric
558 characters only), followed by the literal string "/cryptsetup/",
559 followed by the name of the volume to acquire they key for. Example
560 (for a volume "myvol"):
561 Example 1.
563 \0d7067f78d9827418/cryptsetup/myvol
565 Services listening on the AF_UNIX stream socket may query the source
567 socket name with getpeername(2), and use it to determine which key to
568 send, allowing a single listening socket to serve keys for a multitude
569 of volumes. If the PKCS#11 logic is used (see above) the socket source
570 name is picked in identical fashion, except that the literal string
571 "/cryptsetup-pkcs11/" is used (similar for FIDO2: "/cryptsetup-fido2/"
572 and TPM2: "/cryptsetup-tpm2/"). This is done so that services providing
573 key material know that not a secret key is requested but an encrypted
574 key that will be decrypted via the PKCS#11/FIDO2/TPM2 logic to acquire
575 the final secret key.
576
578 Example 2. /etc/crypttab example
579 Set up four encrypted block devices. One using LUKS for normal storage,
581 another one for usage as a swap device and two TrueCrypt volumes. For
582 the fourth device, the option string is interpreted as two options
583 "cipher=xchacha12,aes-adiantum-plain64", "keyfile-timeout=10s".
584 luks UUID=2505567a-9e27-4efe-a4d5-15ad146c258b
586 swap /dev/sda7 /dev/urandom swap
587 truecrypt /dev/sda2 /etc/container_password tcrypt
588 hidden /mnt/tc_hidden /dev/null tcrypt-hidden,tcrypt-keyfile=/etc/keyfile
589 external /dev/sda3 keyfile:LABEL=keydev keyfile-timeout=10s,cipher=xchacha12\,aes-adiantum-plain64
590 Example 3. Yubikey-based PKCS#11 Volume Unlocking Example
592 The PKCS#11 logic allows hooking up any compatible security token that
594 is capable of storing RSA decryption keys for unlocking an encrypted
595 volume. Here's an example how to set up a Yubikey security token for
596 this purpose on a LUKS2 volume, using ykmap(1) from the yubikey-manager
597 project to initialize the token and systemd-cryptenroll(1) to add it in
598 the LUKS2 volume:
599 # SPDX-License-Identifier: CC0-1.0
601 # Destroy any old key on the Yubikey (careful!)
603 ykman piv reset
604 # Generate a new private/public key pair on the device, store the public key in
606 # 'pubkey.pem'.
607 ykman piv generate-key -a RSA2048 9d pubkey.pem
608 # Create a self-signed certificate from this public key, and store it on the
610 # device. The "subject" should be an arbitrary user-chosen string to identify
611 # the token with.
612 ykman piv generate-certificate --subject "Knobelei" 9d pubkey.pem
613 # We don't need the public key anymore, let's remove it. Since it is not
615 # security sensitive we just do a regular "rm" here.
616 rm pubkey.pem
617 # Enroll the freshly initialized security token in the LUKS2 volume. Replace
619 # /dev/sdXn by the partition to use (e.g. /dev/sda1).
620 sudo systemd-cryptenroll --pkcs11-token-uri=auto /dev/sdXn
621 # Test: Let's run systemd-cryptsetup to test if this all worked.
623 sudo /usr/lib/systemd/systemd-cryptsetup attach mytest /dev/sdXn - pkcs11-uri=auto
624 # If that worked, let's now add the same line persistently to /etc/crypttab,
626 # for the future.
627 sudo bash -c 'echo "mytest /dev/sdXn - pkcs11-uri=auto" >> /etc/crypttab'
628 A few notes on the above:
630 • We use RSA2048, which is the longest key size current Yubikeys
632 support
633 • We use Yubikey key slot 9d, since that's apparently the keyslot to
635 use for decryption purposes, see documentation[2].
636 Example 4. FIDO2 Volume Unlocking Example
638 The FIDO2 logic allows using any compatible FIDO2 security token that
640 implements the "hmac-secret" extension for unlocking an encrypted
641 volume. Here's an example how to set up a FIDO2 security token for this
642 purpose for a LUKS2 volume, using systemd-cryptenroll(1):
643 # SPDX-License-Identifier: CC0-1.0
645 # Enroll the security token in the LUKS2 volume. Replace /dev/sdXn by the
647 # partition to use (e.g. /dev/sda1).
648 sudo systemd-cryptenroll --fido2-device=auto /dev/sdXn
649 # Test: Let's run systemd-cryptsetup to test if this worked.
651 sudo /usr/lib/systemd/systemd-cryptsetup attach mytest /dev/sdXn - fido2-device=auto
652 # If that worked, let's now add the same line persistently to /etc/crypttab,
654 # for the future.
655 sudo bash -c 'echo "mytest /dev/sdXn - fido2-device=auto" >> /etc/crypttab'
656 Example 5. TPM2 Volume Unlocking Example
658 The TPM2 logic allows using any TPM2 chip supported by the Linux kernel
660 for unlocking an encrypted volume. Here's an example how to set up a
661 TPM2 chip for this purpose for a LUKS2 volume, using systemd-
662 cryptenroll(1):
663 # SPDX-License-Identifier: CC0-1.0
665 # Enroll the TPM2 security chip in the LUKS2 volume, and bind it to PCR 7
667 # only. Replace /dev/sdXn by the partition to use (e.g. /dev/sda1).
668 sudo systemd-cryptenroll --tpm2-device=auto --tpm2-pcrs=7 /dev/sdXn
669 # Test: Let's run systemd-cryptsetup to test if this worked.
671 sudo /usr/lib/systemd/systemd-cryptsetup attach mytest /dev/sdXn - tpm2-device=auto
672 # If that worked, let's now add the same line persistently to /etc/crypttab,
674 # for the future.
675 sudo bash -c 'echo "mytest /dev/sdXn - tpm2-device=auto" >> /etc/crypttab'
676
678 systemd(1), systemd-cryptsetup@.service(8), systemd-cryptsetup-
679 generator(8), systemd-cryptenroll(1), fstab(5), cryptsetup(8),
680 mkswap(8), mke2fs(8)
681
683 1. RFC7512 PKCS#11 URI
684 https://tools.ietf.org/html/rfc7512
685 2. see documentation
687 https://developers.yubico.com/PIV/Introduction/Certificate_slots.html
688systemd 250 CRYPTTAB(5)