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45ae1a05 LP |
1 | <?xml version="1.0"?> |
2 | <!--*-nxml-*--> | |
3a54a157 ZJS |
3 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
4 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
45ae1a05 | 5 | <!-- |
572eb058 ZJS |
6 | SPDX-License-Identifier: LGPL-2.1+ |
7 | ||
45ae1a05 LP |
8 | This is based on crypttab(5) from Fedora's initscripts package, which in |
9 | turn is based on Debian's version. | |
10 | ||
11 | The Red Hat version has been written by Miloslav Trmac <mitr@redhat.com>. | |
45ae1a05 | 12 | --> |
c2d54475 | 13 | <refentry id="crypttab" conditional='HAVE_LIBCRYPTSETUP' xmlns:xi="http://www.w3.org/2001/XInclude"> |
45ae1a05 | 14 | |
798d3a52 ZJS |
15 | <refentryinfo> |
16 | <title>crypttab</title> | |
17 | <productname>systemd</productname> | |
798d3a52 ZJS |
18 | </refentryinfo> |
19 | ||
20 | <refmeta> | |
21 | <refentrytitle>crypttab</refentrytitle> | |
22 | <manvolnum>5</manvolnum> | |
23 | </refmeta> | |
24 | ||
25 | <refnamediv> | |
26 | <refname>crypttab</refname> | |
27 | <refpurpose>Configuration for encrypted block devices</refpurpose> | |
28 | </refnamediv> | |
29 | ||
30 | <refsynopsisdiv> | |
31 | <para><filename>/etc/crypttab</filename></para> | |
32 | </refsynopsisdiv> | |
33 | ||
34 | <refsect1> | |
35 | <title>Description</title> | |
36 | ||
37 | <para>The <filename>/etc/crypttab</filename> file describes | |
38 | encrypted block devices that are set up during system boot.</para> | |
39 | ||
40 | <para>Empty lines and lines starting with the <literal>#</literal> | |
41 | character are ignored. Each of the remaining lines describes one | |
ed3657d5 | 42 | encrypted block device. Fields are delimited by white space.</para> |
b2a1a5c7 | 43 | |
6e41f4dd | 44 | <para>Each line is in the form<programlisting><replaceable>volume-name</replaceable> <replaceable>encrypted-device</replaceable> <replaceable>key-file</replaceable> <replaceable>options</replaceable></programlisting> |
b2a1a5c7 | 45 | The first two fields are mandatory, the remaining two are |
798d3a52 ZJS |
46 | optional.</para> |
47 | ||
48 | <para>Setting up encrypted block devices using this file supports | |
49 | three encryption modes: LUKS, TrueCrypt and plain. See | |
3ba3a79d | 50 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
51 | for more information about each mode. When no mode is specified in |
52 | the options field and the block device contains a LUKS signature, | |
53 | it is opened as a LUKS device; otherwise, it is assumed to be in | |
54 | raw dm-crypt (plain mode) format.</para> | |
55 | ||
6e41f4dd LP |
56 | <para>The first field contains the name of the resulting encrypted volume; its block device is set up |
57 | below <filename>/dev/mapper/</filename>.</para> | |
798d3a52 ZJS |
58 | |
59 | <para>The second field contains a path to the underlying block | |
60 | device or file, or a specification of a block device via | |
61 | <literal>UUID=</literal> followed by the UUID.</para> | |
62 | ||
6e41f4dd LP |
63 | <para>The third field specifies an absolute path to a file to read the encryption key from. If the field |
64 | is not present or set to <literal>none</literal> or <literal>-</literal>, a key file named after the | |
65 | volume to unlock (i.e. the first column of the line), suffixed with <filename>.key</filename> is | |
66 | automatically loaded from the <filename>/etc/cryptsetup-keys.d/</filename> and | |
67 | <filename>/run/cryptsetup-keys.d/</filename> directories, if present. Otherwise, the password has to be | |
68 | manually entered during system boot. For swap encryption, <filename>/dev/urandom</filename> may be used | |
69 | as key file.</para> | |
798d3a52 ZJS |
70 | |
71 | <para>The fourth field, if present, is a comma-delimited list of | |
72 | options. The following options are recognized:</para> | |
73 | ||
74 | <variablelist class='fstab-options'> | |
75 | ||
798d3a52 ZJS |
76 | <varlistentry> |
77 | <term><option>cipher=</option></term> | |
78 | ||
79 | <listitem><para>Specifies the cipher to use. See | |
3ba3a79d | 80 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
81 | for possible values and the default value of this option. A |
82 | cipher with unpredictable IV values, such as | |
83 | <literal>aes-cbc-essiv:sha256</literal>, is | |
84 | recommended.</para></listitem> | |
85 | </varlistentry> | |
86 | ||
ed3657d5 ZJS |
87 | <varlistentry> |
88 | <term><option>discard</option></term> | |
89 | ||
90 | <listitem><para>Allow discard requests to be passed through the encrypted block | |
91 | device. This improves performance on SSD storage but has security implications. | |
92 | </para></listitem> | |
93 | </varlistentry> | |
94 | ||
798d3a52 ZJS |
95 | <varlistentry> |
96 | <term><option>hash=</option></term> | |
97 | ||
98 | <listitem><para>Specifies the hash to use for password | |
99 | hashing. See | |
3ba3a79d | 100 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
101 | for possible values and the default value of this |
102 | option.</para></listitem> | |
103 | </varlistentry> | |
104 | ||
105 | <varlistentry> | |
106 | <term><option>header=</option></term> | |
107 | ||
108 | <listitem><para>Use a detached (separated) metadata device or | |
109 | file where the LUKS header is stored. This option is only | |
110 | relevant for LUKS devices. See | |
3ba3a79d | 111 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
112 | for possible values and the default value of this |
113 | option.</para></listitem> | |
114 | </varlistentry> | |
115 | ||
116 | <varlistentry> | |
117 | <term><option>keyfile-offset=</option></term> | |
118 | ||
119 | <listitem><para>Specifies the number of bytes to skip at the | |
120 | start of the key file. See | |
3ba3a79d | 121 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
122 | for possible values and the default value of this |
123 | option.</para></listitem> | |
124 | </varlistentry> | |
125 | ||
126 | <varlistentry> | |
127 | <term><option>keyfile-size=</option></term> | |
128 | ||
129 | <listitem><para>Specifies the maximum number of bytes to read | |
130 | from the key file. See | |
3ba3a79d | 131 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
132 | for possible values and the default value of this option. This |
133 | option is ignored in plain encryption mode, as the key file | |
134 | size is then given by the key size.</para></listitem> | |
135 | </varlistentry> | |
136 | ||
6e41f4dd LP |
137 | <varlistentry> |
138 | <term><option>keyfile-erase</option></term> | |
139 | ||
140 | <listitem><para>If enabled, the specified key file is erased after the volume is activated or when | |
141 | activation fails. This is in particular useful when the key file is only acquired transiently before | |
142 | activation (e.g. via a file in <filename>/run/</filename>, generated by a service running before | |
143 | activation), and shall be removed after use. Defaults to off.</para></listitem> | |
144 | </varlistentry> | |
145 | ||
798d3a52 ZJS |
146 | <varlistentry> |
147 | <term><option>key-slot=</option></term> | |
148 | ||
149 | <listitem><para>Specifies the key slot to compare the | |
150 | passphrase or key against. If the key slot does not match the | |
151 | given passphrase or key, but another would, the setup of the | |
152 | device will fail regardless. This option implies | |
153 | <option>luks</option>. See | |
3ba3a79d | 154 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
155 | for possible values. The default is to try all key slots in |
156 | sequential order.</para></listitem> | |
157 | </varlistentry> | |
158 | ||
4e133451 | 159 | <varlistentry> |
160 | <term><option>keyfile-timeout=</option></term> | |
161 | ||
162 | <listitem><para> Specifies the timeout for the device on | |
163 | which the key file resides and falls back to a password if | |
164 | it could not be mounted. See | |
165 | <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
166 | for key files on external devices. | |
167 | </para></listitem> | |
168 | </varlistentry> | |
169 | ||
798d3a52 ZJS |
170 | <varlistentry> |
171 | <term><option>luks</option></term> | |
172 | ||
173 | <listitem><para>Force LUKS mode. When this mode is used, the | |
174 | following options are ignored since they are provided by the | |
175 | LUKS header on the device: <option>cipher=</option>, | |
176 | <option>hash=</option>, | |
177 | <option>size=</option>.</para></listitem> | |
178 | </varlistentry> | |
179 | ||
b001ad61 ZJS |
180 | <varlistentry> |
181 | <term><option>_netdev</option></term> | |
182 | ||
183 | <listitem><para>Marks this cryptsetup device as requiring network. It will be | |
184 | started after the network is available, similarly to | |
185 | <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
186 | units marked with <option>_netdev</option>. The service unit to set up this device | |
a0dd2097 | 187 | will be ordered between <filename>remote-fs-pre.target</filename> and |
b001ad61 ZJS |
188 | <filename>remote-cryptsetup.target</filename>, instead of |
189 | <filename>cryptsetup-pre.target</filename> and | |
288c2616 ZJS |
190 | <filename>cryptsetup.target</filename>.</para> |
191 | ||
192 | <para>Hint: if this device is used for a mount point that is specified in | |
193 | <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
194 | the <option>_netdev</option> option should also be used for the mount | |
195 | point. Otherwise, a dependency loop might be created where the mount point | |
196 | will be pulled in by <filename>local-fs.target</filename>, while the | |
197 | service to configure the network is usually only started <emphasis>after</emphasis> | |
198 | the local file system has been mounted.</para> | |
199 | </listitem> | |
b001ad61 ZJS |
200 | </varlistentry> |
201 | ||
798d3a52 ZJS |
202 | <varlistentry> |
203 | <term><option>noauto</option></term> | |
204 | ||
5d0e4851 ZJS |
205 | <listitem><para>This device will not be added to <filename>cryptsetup.target</filename>. |
206 | This means that it will not be automatically unlocked on boot, unless something else pulls | |
207 | it in. In particular, if the device is used for a mount point, it'll be unlocked | |
208 | automatically during boot, unless the mount point itself is also disabled with | |
209 | <option>noauto</option>.</para></listitem> | |
798d3a52 ZJS |
210 | </varlistentry> |
211 | ||
212 | <varlistentry> | |
213 | <term><option>nofail</option></term> | |
214 | ||
5d0e4851 | 215 | <listitem><para>This device will not be a hard dependency of |
7792d9cd | 216 | <filename>cryptsetup.target</filename>. It'll still be pulled in and started, but the system |
5d0e4851 ZJS |
217 | will not wait for the device to show up and be unlocked, and boot will not fail if this is |
218 | unsuccessful. Note that other units that depend on the unlocked device may still fail. In | |
7792d9cd AZ |
219 | particular, if the device is used for a mount point, the mount point itself also needs to |
220 | have the <option>nofail</option> option, or the boot will fail if the device is not unlocked | |
5d0e4851 | 221 | successfully.</para></listitem> |
798d3a52 ZJS |
222 | </varlistentry> |
223 | ||
ed3657d5 ZJS |
224 | <varlistentry> |
225 | <term><option>offset=</option></term> | |
226 | ||
227 | <listitem><para>Start offset in the backend device, in 512-byte sectors. This | |
228 | option is only relevant for plain devices.</para></listitem> | |
229 | </varlistentry> | |
230 | ||
798d3a52 ZJS |
231 | <varlistentry> |
232 | <term><option>plain</option></term> | |
233 | ||
234 | <listitem><para>Force plain encryption mode.</para></listitem> | |
235 | </varlistentry> | |
236 | ||
237 | <varlistentry> | |
238 | <term><option>read-only</option></term><term><option>readonly</option></term> | |
239 | ||
240 | <listitem><para>Set up the encrypted block device in read-only | |
241 | mode.</para></listitem> | |
242 | </varlistentry> | |
243 | ||
2c65512e YW |
244 | <varlistentry> |
245 | <term><option>same-cpu-crypt</option></term> | |
246 | ||
247 | <listitem><para>Perform encryption using the same cpu that IO was submitted on. The default is to use | |
248 | an unbound workqueue so that encryption work is automatically balanced between available CPUs.</para> | |
249 | <para>This requires kernel 4.0 or newer.</para> | |
250 | </listitem> | |
251 | </varlistentry> | |
252 | ||
253 | <varlistentry> | |
254 | <term><option>submit-from-crypt-cpus</option></term> | |
255 | ||
256 | <listitem><para>Disable offloading writes to a separate thread after encryption. There are some | |
257 | situations where offloading write bios from the encryption threads to a single thread degrades | |
258 | performance significantly. The default is to offload write bios to the same thread because it benefits | |
259 | CFQ to have writes submitted using the same context.</para> | |
260 | <para>This requires kernel 4.0 or newer.</para> | |
261 | </listitem> | |
262 | </varlistentry> | |
263 | ||
ed3657d5 ZJS |
264 | <varlistentry> |
265 | <term><option>skip=</option></term> | |
266 | ||
267 | <listitem><para>How many 512-byte sectors of the encrypted data to skip at the | |
268 | beginning. This is different from the <option>offset=</option> option with respect | |
269 | to the sector numbers used in initialization vector (IV) calculation. Using | |
270 | <option>offset=</option> will shift the IV calculation by the same negative | |
271 | amount. Hence, if <option>offset=<replaceable>n</replaceable></option> is given, | |
272 | sector <replaceable>n</replaceable> will get a sector number of 0 for the IV | |
273 | calculation. Using <option>skip=</option> causes sector | |
274 | <replaceable>n</replaceable> to also be the first sector of the mapped device, but | |
275 | with its number for IV generation being <replaceable>n</replaceable>.</para> | |
276 | ||
277 | <para>This option is only relevant for plain devices.</para> | |
278 | </listitem> | |
279 | </varlistentry> | |
280 | ||
798d3a52 ZJS |
281 | <varlistentry> |
282 | <term><option>size=</option></term> | |
283 | ||
284 | <listitem><para>Specifies the key size in bits. See | |
3ba3a79d | 285 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
286 | for possible values and the default value of this |
287 | option.</para></listitem> | |
288 | </varlistentry> | |
289 | ||
a9fc6406 DJL |
290 | <varlistentry> |
291 | <term><option>sector-size=</option></term> | |
292 | ||
293 | <listitem><para>Specifies the sector size in bytes. See | |
294 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
295 | for possible values and the default value of this | |
296 | option.</para></listitem> | |
297 | </varlistentry> | |
298 | ||
798d3a52 ZJS |
299 | <varlistentry> |
300 | <term><option>swap</option></term> | |
301 | ||
302 | <listitem><para>The encrypted block device will be used as a | |
303 | swap device, and will be formatted accordingly after setting | |
304 | up the encrypted block device, with | |
305 | <citerefentry project='man-pages'><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
306 | This option implies <option>plain</option>.</para> | |
307 | ||
308 | <para>WARNING: Using the <option>swap</option> option will | |
309 | destroy the contents of the named partition during every boot, | |
310 | so make sure the underlying block device is specified | |
311 | correctly.</para></listitem> | |
312 | </varlistentry> | |
313 | ||
314 | <varlistentry> | |
315 | <term><option>tcrypt</option></term> | |
316 | ||
317 | <listitem><para>Use TrueCrypt encryption mode. When this mode | |
318 | is used, the following options are ignored since they are | |
319 | provided by the TrueCrypt header on the device or do not | |
320 | apply: | |
321 | <option>cipher=</option>, | |
322 | <option>hash=</option>, | |
323 | <option>keyfile-offset=</option>, | |
324 | <option>keyfile-size=</option>, | |
325 | <option>size=</option>.</para> | |
326 | ||
327 | <para>When this mode is used, the passphrase is read from the | |
328 | key file given in the third field. Only the first line of this | |
329 | file is read, excluding the new line character.</para> | |
330 | ||
331 | <para>Note that the TrueCrypt format uses both passphrase and | |
332 | key files to derive a password for the volume. Therefore, the | |
333 | passphrase and all key files need to be provided. Use | |
334 | <option>tcrypt-keyfile=</option> to provide the absolute path | |
335 | to all key files. When using an empty passphrase in | |
336 | combination with one or more key files, use | |
337 | <literal>/dev/null</literal> as the password file in the third | |
338 | field.</para></listitem> | |
339 | </varlistentry> | |
340 | ||
341 | <varlistentry> | |
342 | <term><option>tcrypt-hidden</option></term> | |
343 | ||
344 | <listitem><para>Use the hidden TrueCrypt volume. This option | |
345 | implies <option>tcrypt</option>.</para> | |
346 | ||
347 | <para>This will map the hidden volume that is inside of the | |
348 | volume provided in the second field. Please note that there is | |
349 | no protection for the hidden volume if the outer volume is | |
350 | mounted instead. See | |
3ba3a79d | 351 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
352 | for more information on this limitation.</para></listitem> |
353 | </varlistentry> | |
354 | ||
355 | <varlistentry> | |
356 | <term><option>tcrypt-keyfile=</option></term> | |
357 | ||
358 | <listitem><para>Specifies the absolute path to a key file to | |
359 | use for a TrueCrypt volume. This implies | |
360 | <option>tcrypt</option> and can be used more than once to | |
361 | provide several key files.</para> | |
362 | ||
363 | <para>See the entry for <option>tcrypt</option> on the | |
364 | behavior of the passphrase and key files when using TrueCrypt | |
365 | encryption mode.</para></listitem> | |
366 | </varlistentry> | |
367 | ||
368 | <varlistentry> | |
369 | <term><option>tcrypt-system</option></term> | |
370 | ||
371 | <listitem><para>Use TrueCrypt in system encryption mode. This | |
372 | option implies <option>tcrypt</option>.</para></listitem> | |
373 | </varlistentry> | |
374 | ||
52028838 GH |
375 | <varlistentry> |
376 | <term><option>tcrypt-veracrypt</option></term> | |
377 | ||
378 | <listitem><para>Check for a VeraCrypt volume. VeraCrypt is a fork of | |
379 | TrueCrypt that is mostly compatible, but uses different, stronger key | |
380 | derivation algorithms that cannot be detected without this flag. | |
381 | Enabling this option could substantially slow down unlocking, because | |
382 | VeraCrypt's key derivation takes much longer than TrueCrypt's. This | |
383 | option implies <option>tcrypt</option>.</para></listitem> | |
384 | </varlistentry> | |
385 | ||
798d3a52 ZJS |
386 | <varlistentry> |
387 | <term><option>timeout=</option></term> | |
388 | ||
389 | <listitem><para>Specifies the timeout for querying for a | |
390 | password. If no unit is specified, seconds is used. Supported | |
391 | units are s, ms, us, min, h, d. A timeout of 0 waits | |
392 | indefinitely (which is the default).</para></listitem> | |
393 | </varlistentry> | |
394 | ||
798d3a52 ZJS |
395 | <varlistentry> |
396 | <term><option>tmp</option></term> | |
397 | ||
398 | <listitem><para>The encrypted block device will be prepared | |
399 | for using it as <filename>/tmp</filename>; it will be | |
400 | formatted using | |
401 | <citerefentry project='man-pages'><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
402 | This option implies <option>plain</option>.</para> | |
403 | ||
404 | <para>WARNING: Using the <option>tmp</option> option will | |
405 | destroy the contents of the named partition during every boot, | |
406 | so make sure the underlying block device is specified | |
407 | correctly.</para></listitem> | |
408 | </varlistentry> | |
409 | ||
410 | <varlistentry> | |
411 | <term><option>tries=</option></term> | |
412 | ||
413 | <listitem><para>Specifies the maximum number of times the user | |
414 | is queried for a password. The default is 3. If set to 0, the | |
415 | user is queried for a password indefinitely.</para></listitem> | |
416 | </varlistentry> | |
417 | ||
418 | <varlistentry> | |
419 | <term><option>verify</option></term> | |
420 | ||
c2d54475 LP |
421 | <listitem><para>If the encryption password is read from console, it has to be entered twice to |
422 | prevent typos.</para></listitem> | |
423 | </varlistentry> | |
424 | ||
425 | <varlistentry> | |
426 | <term><option>pkcs11-uri=</option></term> | |
427 | ||
428 | <listitem><para>Takes a <ulink url="https://tools.ietf.org/html/rfc7512">RFC7512 PKCS#11 URI</ulink> | |
429 | pointing to a private RSA key which is used to decrypt the key specified in the third column of the | |
430 | line. This is useful for unlocking encrypted volumes through security tokens or smartcards. See below | |
431 | for an example how to set up this mechanism for unlocking a LUKS volume with a YubiKey security | |
432 | token. The specified URI can refer directly to a private RSA key stored on a token or alternatively | |
2ccf0ff6 LP |
433 | just to a slot or token, in which case a search for a suitable private RSA key will be performed. In |
434 | this case if multiple suitable objects are found the token is refused. The key configured in the | |
435 | third column is passed as is to RSA decryption. The resulting decrypted key is then base64 encoded | |
436 | before it is used to unlock the LUKS volume.</para></listitem> | |
798d3a52 ZJS |
437 | </varlistentry> |
438 | ||
6e41f4dd LP |
439 | <varlistentry> |
440 | <term><option>try-empty-password=</option></term> | |
441 | ||
442 | <listitem><para>Takes a boolean argument. If enabled, right before asking the user for a password it | |
443 | is first attempted to unlock the volume with an empty password. This is useful for systems that are | |
444 | initialized with an encrypted volume with only an empty password set, which shall be replaced with a | |
445 | suitable password during first boot, but after activation.</para></listitem> | |
446 | </varlistentry> | |
447 | ||
ed3657d5 ZJS |
448 | <varlistentry> |
449 | <term><option>x-systemd.device-timeout=</option></term> | |
450 | ||
451 | <listitem><para>Specifies how long systemd should wait for a device to show up | |
452 | before giving up on the entry. The argument is a time in seconds or explicitly | |
453 | specified units of | |
454 | <literal>s</literal>, | |
455 | <literal>min</literal>, | |
456 | <literal>h</literal>, | |
457 | <literal>ms</literal>. | |
458 | </para></listitem> | |
459 | </varlistentry> | |
460 | ||
1dc85eff FB |
461 | <varlistentry> |
462 | <term><option>x-initrd.attach</option></term> | |
463 | ||
464 | <listitem><para>Setup this encrypted block device in the initramfs, similarly to | |
465 | <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
466 | units marked with <option>x-initrd.mount</option>.</para> | |
467 | ||
468 | <para>Although it's not necessary to mark the mount entry for the root file system with | |
469 | <option>x-initrd.mount</option>, <option>x-initrd.attach</option> is still recommended with | |
470 | the encrypted block device containing the root file system as otherwise systemd will | |
471 | attempt to detach the device during the regular system shutdown while it's still in | |
472 | use. With this option the device will still be detached but later after the root file | |
473 | system is unmounted.</para> | |
474 | ||
475 | <para>All other encrypted block devices that contain file systems mounted in the initramfs | |
476 | should use this option.</para> | |
477 | </listitem> | |
478 | </varlistentry> | |
479 | ||
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480 | </variablelist> |
481 | ||
482 | <para>At early boot and when the system manager configuration is | |
483 | reloaded, this file is translated into native systemd units by | |
484 | <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para> | |
485 | </refsect1> | |
486 | ||
487 | <refsect1> | |
c2d54475 | 488 | <title>Examples</title> |
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489 | <example> |
490 | <title>/etc/crypttab example</title> | |
491 | <para>Set up four encrypted block devices. One using LUKS for | |
492 | normal storage, another one for usage as a swap device and two | |
493 | TrueCrypt volumes.</para> | |
494 | ||
495 | <programlisting>luks UUID=2505567a-9e27-4efe-a4d5-15ad146c258b | |
496 | swap /dev/sda7 /dev/urandom swap | |
8cf3ca80 | 497 | truecrypt /dev/sda2 /etc/container_password tcrypt |
4e133451 | 498 | hidden /mnt/tc_hidden /dev/null tcrypt-hidden,tcrypt-keyfile=/etc/keyfile |
499 | external /dev/sda3 keyfile:LABEL=keydev keyfile-timeout=10s</programlisting> | |
798d3a52 | 500 | </example> |
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501 | |
502 | <example> | |
503 | <title>Yubikey-based Volume Unlocking Example</title> | |
504 | ||
505 | <para>The PKCS#11 logic allows hooking up any compatible security token that is capable of storing RSA | |
2ccf0ff6 LP |
506 | decryption keys. Here's an example how to set up a Yubikey security token for this purpose, using |
507 | <command>ykman</command> from the yubikey-manager project:</para> | |
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508 | |
509 | <programlisting><xi:include href="yubikey-crypttab.sh" parse="text" /></programlisting> | |
510 | ||
511 | <para>A few notes on the above:</para> | |
512 | ||
513 | <itemizedlist> | |
514 | <listitem><para>We use RSA (and not ECC), since Yubikeys support PKCS#11 Decrypt() only for RSA keys</para></listitem> | |
515 | <listitem><para>We use RSA2048, which is the longest key size current Yubikeys support</para></listitem> | |
516 | <listitem><para>LUKS key size must be shorter than 2048bit due to RSA padding, hence we use 128 bytes</para></listitem> | |
517 | <listitem><para>We use Yubikey key slot 9d, since that's apparently the keyslot to use for decryption purposes, | |
518 | <ulink url="https://developers.yubico.com/PIV/Introduction/Certificate_slots.html">see | |
519 | documentation</ulink>.</para></listitem> | |
520 | </itemizedlist> | |
521 | ||
522 | </example> | |
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523 | </refsect1> |
524 | ||
525 | <refsect1> | |
526 | <title>See Also</title> | |
527 | <para> | |
528 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
529 | <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
530 | <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
288c2616 | 531 | <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
3ba3a79d | 532 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
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533 | <citerefentry project='man-pages'><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
534 | <citerefentry project='man-pages'><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
535 | </para> | |
536 | </refsect1> | |
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537 | |
538 | </refentry> |