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1 | <?xml version="1.0"?> |
2 | <!--*-nxml-*--> | |
12b42c76 | 3 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | <!-- |
5 | This file is part of systemd. | |
6 | ||
7 | Copyright 2012 Lennart Poettering | |
8 | ||
9 | systemd is free software; you can redistribute it and/or modify it | |
10 | under the terms of the GNU Lesser General Public License as published by | |
11 | the Free Software Foundation; either version 2.1 of the License, or | |
12 | (at your option) any later version. | |
13 | ||
14 | systemd is distributed in the hope that it will be useful, but | |
15 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | Lesser General Public License for more details. | |
18 | ||
19 | You should have received a copy of the GNU Lesser General Public License | |
20 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
21 | ||
22 | This is based on crypttab(5) from Fedora's initscripts package, which in | |
23 | turn is based on Debian's version. | |
24 | ||
25 | The Red Hat version has been written by Miloslav Trmac <mitr@redhat.com>. | |
26 | ||
27 | --> | |
56ba3c78 | 28 | <refentry id="crypttab" conditional='HAVE_LIBCRYPTSETUP'> |
45ae1a05 | 29 | |
798d3a52 ZJS |
30 | <refentryinfo> |
31 | <title>crypttab</title> | |
32 | <productname>systemd</productname> | |
33 | ||
34 | <authorgroup> | |
35 | <author> | |
36 | <contrib>Documentation</contrib> | |
37 | <firstname>Miloslav</firstname> | |
38 | <surname>Trmac</surname> | |
39 | <email>mitr@redhat.com</email> | |
40 | </author> | |
41 | <author> | |
42 | <contrib>Documentation</contrib> | |
43 | <firstname>Lennart</firstname> | |
44 | <surname>Poettering</surname> | |
45 | <email>lennart@poettering.net</email> | |
46 | </author> | |
47 | </authorgroup> | |
48 | </refentryinfo> | |
49 | ||
50 | <refmeta> | |
51 | <refentrytitle>crypttab</refentrytitle> | |
52 | <manvolnum>5</manvolnum> | |
53 | </refmeta> | |
54 | ||
55 | <refnamediv> | |
56 | <refname>crypttab</refname> | |
57 | <refpurpose>Configuration for encrypted block devices</refpurpose> | |
58 | </refnamediv> | |
59 | ||
60 | <refsynopsisdiv> | |
61 | <para><filename>/etc/crypttab</filename></para> | |
62 | </refsynopsisdiv> | |
63 | ||
64 | <refsect1> | |
65 | <title>Description</title> | |
66 | ||
67 | <para>The <filename>/etc/crypttab</filename> file describes | |
68 | encrypted block devices that are set up during system boot.</para> | |
69 | ||
70 | <para>Empty lines and lines starting with the <literal>#</literal> | |
71 | character are ignored. Each of the remaining lines describes one | |
72 | encrypted block device, fields on the line are delimited by white | |
73 | space. The first two fields are mandatory, the remaining two are | |
74 | optional.</para> | |
75 | ||
76 | <para>Setting up encrypted block devices using this file supports | |
77 | three encryption modes: LUKS, TrueCrypt and plain. See | |
3ba3a79d | 78 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
79 | for more information about each mode. When no mode is specified in |
80 | the options field and the block device contains a LUKS signature, | |
81 | it is opened as a LUKS device; otherwise, it is assumed to be in | |
82 | raw dm-crypt (plain mode) format.</para> | |
83 | ||
84 | <para>The first field contains the name of the resulting encrypted | |
85 | block device; the device is set up within | |
86 | <filename>/dev/mapper/</filename>.</para> | |
87 | ||
88 | <para>The second field contains a path to the underlying block | |
89 | device or file, or a specification of a block device via | |
90 | <literal>UUID=</literal> followed by the UUID.</para> | |
91 | ||
92 | <para>The third field specifies the encryption password. If the | |
93 | field is not present or the password is set to | |
94 | <literal>none</literal> or <literal>-</literal>, the password has | |
95 | to be manually entered during system boot. Otherwise, the field is | |
037a3ded | 96 | interpreted as an absolute path to a file containing the encryption |
798d3a52 ZJS |
97 | password. For swap encryption, <filename>/dev/urandom</filename> |
98 | or the hardware device <filename>/dev/hw_random</filename> can be | |
99 | used as the password file; using <filename>/dev/random</filename> | |
100 | may prevent boot completion if the system does not have enough | |
101 | entropy to generate a truly random encryption key.</para> | |
102 | ||
103 | <para>The fourth field, if present, is a comma-delimited list of | |
104 | options. The following options are recognized:</para> | |
105 | ||
106 | <variablelist class='fstab-options'> | |
107 | ||
108 | <varlistentry> | |
109 | <term><option>discard</option></term> | |
110 | ||
111 | <listitem><para>Allow discard requests to be passed through | |
112 | the encrypted block device. This improves performance on SSD | |
113 | storage but has security implications.</para></listitem> | |
114 | </varlistentry> | |
115 | ||
116 | <varlistentry> | |
117 | <term><option>cipher=</option></term> | |
118 | ||
119 | <listitem><para>Specifies the cipher to use. See | |
3ba3a79d | 120 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
121 | for possible values and the default value of this option. A |
122 | cipher with unpredictable IV values, such as | |
123 | <literal>aes-cbc-essiv:sha256</literal>, is | |
124 | recommended.</para></listitem> | |
125 | </varlistentry> | |
126 | ||
127 | <varlistentry> | |
128 | <term><option>hash=</option></term> | |
129 | ||
130 | <listitem><para>Specifies the hash to use for password | |
131 | hashing. See | |
3ba3a79d | 132 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
133 | for possible values and the default value of this |
134 | option.</para></listitem> | |
135 | </varlistentry> | |
136 | ||
137 | <varlistentry> | |
138 | <term><option>header=</option></term> | |
139 | ||
140 | <listitem><para>Use a detached (separated) metadata device or | |
141 | file where the LUKS header is stored. This option is only | |
142 | relevant for LUKS devices. See | |
3ba3a79d | 143 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
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144 | for possible values and the default value of this |
145 | option.</para></listitem> | |
146 | </varlistentry> | |
147 | ||
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148 | <varlistentry> |
149 | <term><option>offset=</option></term> | |
150 | ||
151 | <listitem><para>Start offset in the backend device, in 512-byte sectors. | |
152 | This option is only relevant for plain devices. | |
153 | </para></listitem> | |
154 | </varlistentry> | |
155 | ||
156 | <varlistentry> | |
157 | <term><option>skip=</option></term> | |
158 | ||
159 | <listitem><para>How many 512-byte sectors of the encrypted data to skip | |
160 | at the beginning. This is different from the <option>--offset</option> | |
161 | option with respect to the sector numbers used in initialization vector | |
162 | (IV) calculation. Using <option>--offset</option> will shift the IV | |
a8eaaee7 | 163 | calculation by the same negative amount. Hence, if <option>--offset n</option> is given, |
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164 | sector n will get a sector number of 0 for the IV calculation. |
165 | Using <option>--skip</option> causes sector n to also be the first | |
a8eaaee7 | 166 | sector of the mapped device, but with its number for IV generation being n.</para> |
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167 | |
168 | <para>This option is only relevant for plain devices.</para> | |
169 | </listitem> | |
170 | </varlistentry> | |
171 | ||
798d3a52 ZJS |
172 | <varlistentry> |
173 | <term><option>keyfile-offset=</option></term> | |
174 | ||
175 | <listitem><para>Specifies the number of bytes to skip at the | |
176 | start of the key file. See | |
3ba3a79d | 177 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
178 | for possible values and the default value of this |
179 | option.</para></listitem> | |
180 | </varlistentry> | |
181 | ||
182 | <varlistentry> | |
183 | <term><option>keyfile-size=</option></term> | |
184 | ||
185 | <listitem><para>Specifies the maximum number of bytes to read | |
186 | from the key file. See | |
3ba3a79d | 187 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
798d3a52 ZJS |
188 | for possible values and the default value of this option. This |
189 | option is ignored in plain encryption mode, as the key file | |
190 | size is then given by the key size.</para></listitem> | |
191 | </varlistentry> | |
192 | ||
193 | <varlistentry> | |
194 | <term><option>key-slot=</option></term> | |
195 | ||
196 | <listitem><para>Specifies the key slot to compare the | |
197 | passphrase or key against. If the key slot does not match the | |
198 | given passphrase or key, but another would, the setup of the | |
199 | device will fail regardless. This option implies | |
200 | <option>luks</option>. See | |
3ba3a79d | 201 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
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202 | for possible values. The default is to try all key slots in |
203 | sequential order.</para></listitem> | |
204 | </varlistentry> | |
205 | ||
206 | <varlistentry> | |
207 | <term><option>luks</option></term> | |
208 | ||
209 | <listitem><para>Force LUKS mode. When this mode is used, the | |
210 | following options are ignored since they are provided by the | |
211 | LUKS header on the device: <option>cipher=</option>, | |
212 | <option>hash=</option>, | |
213 | <option>size=</option>.</para></listitem> | |
214 | </varlistentry> | |
215 | ||
216 | <varlistentry> | |
217 | <term><option>noauto</option></term> | |
218 | ||
219 | <listitem><para>This device will not be automatically unlocked | |
220 | on boot.</para></listitem> | |
221 | </varlistentry> | |
222 | ||
223 | <varlistentry> | |
224 | <term><option>nofail</option></term> | |
225 | ||
226 | <listitem><para>The system will not wait for the device to | |
227 | show up and be unlocked at boot, and not fail the boot if it | |
228 | does not show up.</para></listitem> | |
229 | </varlistentry> | |
230 | ||
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 | ||
244 | <varlistentry> | |
245 | <term><option>size=</option></term> | |
246 | ||
247 | <listitem><para>Specifies the key size in bits. See | |
3ba3a79d | 248 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
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249 | for possible values and the default value of this |
250 | option.</para></listitem> | |
251 | </varlistentry> | |
252 | ||
253 | <varlistentry> | |
254 | <term><option>swap</option></term> | |
255 | ||
256 | <listitem><para>The encrypted block device will be used as a | |
257 | swap device, and will be formatted accordingly after setting | |
258 | up the encrypted block device, with | |
259 | <citerefentry project='man-pages'><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
260 | This option implies <option>plain</option>.</para> | |
261 | ||
262 | <para>WARNING: Using the <option>swap</option> option will | |
263 | destroy the contents of the named partition during every boot, | |
264 | so make sure the underlying block device is specified | |
265 | correctly.</para></listitem> | |
266 | </varlistentry> | |
267 | ||
268 | <varlistentry> | |
269 | <term><option>tcrypt</option></term> | |
270 | ||
271 | <listitem><para>Use TrueCrypt encryption mode. When this mode | |
272 | is used, the following options are ignored since they are | |
273 | provided by the TrueCrypt header on the device or do not | |
274 | apply: | |
275 | <option>cipher=</option>, | |
276 | <option>hash=</option>, | |
277 | <option>keyfile-offset=</option>, | |
278 | <option>keyfile-size=</option>, | |
279 | <option>size=</option>.</para> | |
280 | ||
281 | <para>When this mode is used, the passphrase is read from the | |
282 | key file given in the third field. Only the first line of this | |
283 | file is read, excluding the new line character.</para> | |
284 | ||
285 | <para>Note that the TrueCrypt format uses both passphrase and | |
286 | key files to derive a password for the volume. Therefore, the | |
287 | passphrase and all key files need to be provided. Use | |
288 | <option>tcrypt-keyfile=</option> to provide the absolute path | |
289 | to all key files. When using an empty passphrase in | |
290 | combination with one or more key files, use | |
291 | <literal>/dev/null</literal> as the password file in the third | |
292 | field.</para></listitem> | |
293 | </varlistentry> | |
294 | ||
295 | <varlistentry> | |
296 | <term><option>tcrypt-hidden</option></term> | |
297 | ||
298 | <listitem><para>Use the hidden TrueCrypt volume. This option | |
299 | implies <option>tcrypt</option>.</para> | |
300 | ||
301 | <para>This will map the hidden volume that is inside of the | |
302 | volume provided in the second field. Please note that there is | |
303 | no protection for the hidden volume if the outer volume is | |
304 | mounted instead. See | |
3ba3a79d | 305 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
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306 | for more information on this limitation.</para></listitem> |
307 | </varlistentry> | |
308 | ||
309 | <varlistentry> | |
310 | <term><option>tcrypt-keyfile=</option></term> | |
311 | ||
312 | <listitem><para>Specifies the absolute path to a key file to | |
313 | use for a TrueCrypt volume. This implies | |
314 | <option>tcrypt</option> and can be used more than once to | |
315 | provide several key files.</para> | |
316 | ||
317 | <para>See the entry for <option>tcrypt</option> on the | |
318 | behavior of the passphrase and key files when using TrueCrypt | |
319 | encryption mode.</para></listitem> | |
320 | </varlistentry> | |
321 | ||
322 | <varlistentry> | |
323 | <term><option>tcrypt-system</option></term> | |
324 | ||
325 | <listitem><para>Use TrueCrypt in system encryption mode. This | |
326 | option implies <option>tcrypt</option>.</para></listitem> | |
327 | </varlistentry> | |
328 | ||
329 | <varlistentry> | |
330 | <term><option>timeout=</option></term> | |
331 | ||
332 | <listitem><para>Specifies the timeout for querying for a | |
333 | password. If no unit is specified, seconds is used. Supported | |
334 | units are s, ms, us, min, h, d. A timeout of 0 waits | |
335 | indefinitely (which is the default).</para></listitem> | |
336 | </varlistentry> | |
337 | ||
338 | <varlistentry> | |
339 | <term><option>x-systemd.device-timeout=</option></term> | |
340 | ||
341 | <listitem><para>Specifies how long systemd should wait for a | |
342 | device to show up before giving up on the entry. The argument | |
343 | is a time in seconds or explicitly specified units of | |
344 | <literal>s</literal>, | |
345 | <literal>min</literal>, | |
346 | <literal>h</literal>, | |
347 | <literal>ms</literal>. | |
348 | </para></listitem> | |
349 | </varlistentry> | |
350 | ||
351 | <varlistentry> | |
352 | <term><option>tmp</option></term> | |
353 | ||
354 | <listitem><para>The encrypted block device will be prepared | |
355 | for using it as <filename>/tmp</filename>; it will be | |
356 | formatted using | |
357 | <citerefentry project='man-pages'><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
358 | This option implies <option>plain</option>.</para> | |
359 | ||
360 | <para>WARNING: Using the <option>tmp</option> option will | |
361 | destroy the contents of the named partition during every boot, | |
362 | so make sure the underlying block device is specified | |
363 | correctly.</para></listitem> | |
364 | </varlistentry> | |
365 | ||
366 | <varlistentry> | |
367 | <term><option>tries=</option></term> | |
368 | ||
369 | <listitem><para>Specifies the maximum number of times the user | |
370 | is queried for a password. The default is 3. If set to 0, the | |
371 | user is queried for a password indefinitely.</para></listitem> | |
372 | </varlistentry> | |
373 | ||
374 | <varlistentry> | |
375 | <term><option>verify</option></term> | |
376 | ||
377 | <listitem><para> If the encryption password is read from | |
378 | console, it has to be entered twice to prevent | |
379 | typos.</para></listitem> | |
380 | </varlistentry> | |
381 | ||
382 | </variablelist> | |
383 | ||
384 | <para>At early boot and when the system manager configuration is | |
385 | reloaded, this file is translated into native systemd units by | |
386 | <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para> | |
387 | </refsect1> | |
388 | ||
389 | <refsect1> | |
390 | <title>Example</title> | |
391 | <example> | |
392 | <title>/etc/crypttab example</title> | |
393 | <para>Set up four encrypted block devices. One using LUKS for | |
394 | normal storage, another one for usage as a swap device and two | |
395 | TrueCrypt volumes.</para> | |
396 | ||
397 | <programlisting>luks UUID=2505567a-9e27-4efe-a4d5-15ad146c258b | |
398 | swap /dev/sda7 /dev/urandom swap | |
8cf3ca80 | 399 | truecrypt /dev/sda2 /etc/container_password tcrypt |
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400 | hidden /mnt/tc_hidden /dev/null tcrypt-hidden,tcrypt-keyfile=/etc/keyfile</programlisting> |
401 | </example> | |
402 | </refsect1> | |
403 | ||
404 | <refsect1> | |
405 | <title>See Also</title> | |
406 | <para> | |
407 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
408 | <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
409 | <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
3ba3a79d | 410 | <citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
798d3a52 ZJS |
411 | <citerefentry project='man-pages'><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
412 | <citerefentry project='man-pages'><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
413 | </para> | |
414 | </refsect1> | |
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415 | |
416 | </refentry> |