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1 | <?xml version="1.0"?> |
2 | <!--*-nxml-*--> | |
3 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> | |
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 LP |
29 | |
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 | |
68 | describes encrypted block devices that are set up | |
69 | during system boot.</para> | |
70 | ||
909f413d | 71 | <para>Empty lines and lines starting with the <literal>#</literal> |
45ae1a05 LP |
72 | character are ignored. Each of the remaining lines |
73 | describes one encrypted block device, fields on the | |
74 | line are delimited by white space. The first two | |
75 | fields are mandatory, the remaining two are | |
76 | optional.</para> | |
77 | ||
8cf3ca80 JJ |
78 | <para>Setting up encrypted block devices using this file |
79 | supports three encryption modes: LUKS, TrueCrypt and plain. | |
80 | See <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
81 | for more information about each mode. When no mode is specified | |
82 | in the options field and the block device contains a LUKS | |
83 | signature, it is opened as a LUKS device; otherwise, it is | |
84 | assumed to be in raw dm-crypt (plain mode) format.</para> | |
85 | ||
45ae1a05 LP |
86 | <para>The first field contains the name of the |
87 | resulting encrypted block device; the device is set up | |
88 | within <filename>/dev/mapper/</filename>.</para> | |
89 | ||
90 | <para>The second field contains a path to the | |
8cf3ca80 | 91 | underlying block device or file, or a specification of a block |
45ae1a05 | 92 | device via <literal>UUID=</literal> followed by the |
8cf3ca80 | 93 | UUID.</para> |
45ae1a05 LP |
94 | |
95 | <para>The third field specifies the encryption | |
96 | password. If the field is not present or the password | |
8cf3ca80 JJ |
97 | is set to <literal>none</literal> or <literal>-</literal>, |
98 | the password has to be manually entered during system boot. | |
99 | Otherwise, the field is interpreted as a absolute path to | |
100 | a file containing the encryption password. For swap encryption, | |
45ae1a05 LP |
101 | <filename>/dev/urandom</filename> or the hardware |
102 | device <filename>/dev/hw_random</filename> can be used | |
103 | as the password file; using | |
104 | <filename>/dev/random</filename> may prevent boot | |
105 | completion if the system does not have enough entropy | |
106 | to generate a truly random encryption key.</para> | |
107 | ||
108 | <para>The fourth field, if present, is a | |
109 | comma-delimited list of options. The following | |
110 | options are recognized:</para> | |
111 | ||
ccc9a4f9 | 112 | <variablelist class='crypttab-options'> |
8cf3ca80 JJ |
113 | |
114 | <varlistentry> | |
1acbb95c | 115 | <term><varname>discard</varname></term> |
8cf3ca80 JJ |
116 | |
117 | <listitem><para>Allow discard requests to be | |
118 | passed through the encrypted block device. This | |
119 | improves performance on SSD storage but has | |
120 | security implications.</para></listitem> | |
121 | </varlistentry> | |
122 | ||
45ae1a05 LP |
123 | <varlistentry> |
124 | <term><varname>cipher=</varname></term> | |
125 | ||
8cf3ca80 | 126 | <listitem><para>Specifies the cipher to use. See |
45ae1a05 | 127 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
8cf3ca80 JJ |
128 | for possible values and the default value of |
129 | this option. A cipher with unpredictable IV | |
130 | values, such as <literal>aes-cbc-essiv:sha256</literal>, | |
131 | is recommended.</para></listitem> | |
45ae1a05 LP |
132 | </varlistentry> |
133 | ||
45ae1a05 | 134 | <varlistentry> |
8cf3ca80 | 135 | <term><varname>hash=</varname></term> |
45ae1a05 | 136 | |
8cf3ca80 JJ |
137 | <listitem><para>Specifies the hash to use for |
138 | password hashing. See | |
45ae1a05 | 139 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
8cf3ca80 JJ |
140 | for possible values and the default value of |
141 | this option.</para></listitem> | |
45ae1a05 LP |
142 | </varlistentry> |
143 | ||
8cf3ca80 JJ |
144 | <varlistentry> |
145 | <term><varname>keyfile-offset=</varname></term> | |
146 | ||
147 | <listitem><para>Specifies the number of bytes to | |
148 | skip at the start of the key file. See | |
149 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
150 | for possible values and the default value of | |
151 | this option.</para></listitem> | |
152 | </varlistentry> | |
45ae1a05 | 153 | |
4271d823 TG |
154 | <varlistentry> |
155 | <term><varname>keyfile-size=</varname></term> | |
156 | ||
157 | <listitem><para>Specifies the maximum number | |
8cf3ca80 | 158 | of bytes to read from the key file. See |
4271d823 | 159 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> |
8cf3ca80 JJ |
160 | for possible values and the default value of |
161 | this option. This option is ignored in plain | |
162 | encryption mode, as the key file size is then | |
163 | given by the key size.</para></listitem> | |
4271d823 TG |
164 | </varlistentry> |
165 | ||
880a599e | 166 | <varlistentry> |
8cf3ca80 | 167 | <term><varname>luks</varname></term> |
880a599e | 168 | |
8cf3ca80 | 169 | <listitem><para>Force LUKS mode. When this mode |
fbce1139 | 170 | is used, the following options are ignored since |
8cf3ca80 JJ |
171 | they are provided by the LUKS header on the |
172 | device: <varname>cipher=</varname>, | |
173 | <varname>hash=</varname>, | |
174 | <varname>size=</varname>.</para></listitem> | |
880a599e TG |
175 | </varlistentry> |
176 | ||
45ae1a05 | 177 | <varlistentry> |
8cf3ca80 | 178 | <term><varname>noauto</varname></term> |
45ae1a05 | 179 | |
8cf3ca80 JJ |
180 | <listitem><para>This device will not be |
181 | automatically unlocked on boot.</para></listitem> | |
45ae1a05 LP |
182 | </varlistentry> |
183 | ||
184 | <varlistentry> | |
8cf3ca80 | 185 | <term><varname>nofail</varname></term> |
45ae1a05 | 186 | |
8cf3ca80 JJ |
187 | <listitem><para>The system will not wait for the |
188 | device to show up and be unlocked at boot, and | |
189 | not fail the boot if it does not show up.</para></listitem> | |
45ae1a05 LP |
190 | </varlistentry> |
191 | ||
192 | <varlistentry> | |
8cf3ca80 | 193 | <term><varname>plain</varname></term> |
45ae1a05 | 194 | |
8cf3ca80 | 195 | <listitem><para>Force plain encryption mode.</para></listitem> |
45ae1a05 LP |
196 | </varlistentry> |
197 | ||
198 | <varlistentry> | |
18cf1a1b | 199 | <term><varname>read-only</varname></term><term><varname>readonly</varname></term> |
45ae1a05 | 200 | |
8cf3ca80 JJ |
201 | <listitem><para>Set up the encrypted block |
202 | device in read-only mode.</para></listitem> | |
45ae1a05 LP |
203 | </varlistentry> |
204 | ||
205 | <varlistentry> | |
8cf3ca80 | 206 | <term><varname>size=</varname></term> |
45ae1a05 | 207 | |
8cf3ca80 JJ |
208 | <listitem><para>Specifies the key size |
209 | in bits. See | |
210 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
211 | for possible values and the default value of | |
212 | this option.</para></listitem> | |
45ae1a05 LP |
213 | </varlistentry> |
214 | ||
215 | <varlistentry> | |
8cf3ca80 | 216 | <term><varname>swap</varname></term> |
45ae1a05 | 217 | |
8cf3ca80 JJ |
218 | <listitem><para>The encrypted block device will |
219 | be used as a swap device, and will be formatted | |
220 | accordingly after setting up the encrypted | |
221 | block device, with | |
222 | <citerefentry><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
223 | This option implies <varname>plain</varname>.</para> | |
224 | ||
225 | <para>WARNING: Using the <varname>swap</varname> | |
226 | option will destroy the contents of the named | |
227 | partition during every boot, so make sure the | |
228 | underlying block device is specified correctly.</para></listitem> | |
45ae1a05 LP |
229 | </varlistentry> |
230 | ||
231 | <varlistentry> | |
8cf3ca80 JJ |
232 | <term><varname>tcrypt</varname></term> |
233 | ||
234 | <listitem><para>Use TrueCrypt encryption mode. | |
fbce1139 | 235 | When this mode is used, the following options are |
8cf3ca80 JJ |
236 | ignored since they are provided by the TrueCrypt |
237 | header on the device or do not apply: | |
238 | <varname>cipher=</varname>, | |
239 | <varname>hash=</varname>, | |
240 | <varname>keyfile-offset=</varname>, | |
241 | <varname>keyfile-size=</varname>, | |
242 | <varname>size=</varname>.</para> | |
243 | ||
244 | <para>When this mode is used, the passphrase is | |
245 | read from the key file given in the third field. | |
246 | Only the first line of this file is read, | |
247 | excluding the new line character.</para> | |
248 | ||
249 | <para>Note that the TrueCrypt format uses both | |
250 | passphrase and key files to derive a password | |
251 | for the volume. Therefore, the passphrase and | |
252 | all key files need to be provided. Use | |
253 | <varname>tcrypt-keyfile=</varname> to provide | |
254 | the absolute path to all key files. When using | |
255 | an empty passphrase in combination with one or | |
256 | more key files, use <literal>/dev/null</literal> | |
257 | as the password file in the third field.</para></listitem> | |
258 | </varlistentry> | |
45ae1a05 | 259 | |
8cf3ca80 JJ |
260 | <varlistentry> |
261 | <term><varname>tcrypt-hidden</varname></term> | |
262 | ||
263 | <listitem><para>Use the hidden TrueCrypt volume. | |
264 | This implies <varname>tcrypt</varname>.</para> | |
265 | ||
266 | <para>This will map the hidden volume that is | |
267 | inside of the volume provided in the second | |
268 | field. Please note that there is no protection | |
269 | for the hidden volume if the outer volume is | |
270 | mounted instead. See | |
271 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
272 | for more information on this limitation.</para></listitem> | |
45ae1a05 LP |
273 | </varlistentry> |
274 | ||
275 | <varlistentry> | |
8cf3ca80 JJ |
276 | <term><varname>tcrypt-keyfile=</varname></term> |
277 | ||
278 | <listitem><para>Specifies the absolute path to a | |
279 | key file to use for a TrueCrypt volume. This | |
280 | implies <varname>tcrypt</varname> and can be | |
281 | used more than once to provide several key | |
282 | files.</para> | |
45ae1a05 | 283 | |
8cf3ca80 JJ |
284 | <para>See the entry for <varname>tcrypt</varname> |
285 | on the behavior of the passphrase and key files | |
286 | when using TrueCrypt encryption mode.</para></listitem> | |
45ae1a05 LP |
287 | </varlistentry> |
288 | ||
289 | <varlistentry> | |
8cf3ca80 JJ |
290 | <term><varname>tcrypt-system</varname></term> |
291 | ||
292 | <listitem><para>Use TrueCrypt in system | |
293 | encryption mode. This implies | |
294 | <varname>tcrypt</varname>.</para> | |
295 | ||
296 | <para>Please note that when using this mode, the | |
297 | whole device needs to be given in the second | |
298 | field instead of the partition. For example: if | |
299 | <literal>/dev/sda2</literal> is the system | |
300 | encrypted TrueCrypt patition, <literal>/dev/sda</literal> | |
301 | has to be given.</para></listitem> | |
302 | </varlistentry> | |
303 | ||
304 | <varlistentry> | |
305 | <term><varname>timeout=</varname></term> | |
45ae1a05 | 306 | |
8cf3ca80 JJ |
307 | <listitem><para>Specifies the timeout for |
308 | querying for a password. If no unit is | |
309 | specified, seconds is used. Supported units are | |
310 | s, ms, us, min, h, d. A timeout of 0 waits | |
311 | indefinitely (which is the default).</para></listitem> | |
45ae1a05 LP |
312 | </varlistentry> |
313 | ||
314 | <varlistentry> | |
8cf3ca80 JJ |
315 | <term><varname>tmp</varname></term> |
316 | ||
317 | <listitem><para>The encrypted block device will | |
318 | be prepared for using it as <filename>/tmp</filename>; | |
319 | it will be formatted using | |
320 | <citerefentry><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
321 | This option implies <varname>plain</varname>.</para> | |
45ae1a05 | 322 | |
8cf3ca80 JJ |
323 | <para>WARNING: Using the <varname>tmp</varname> |
324 | option will destroy the contents of the named | |
325 | partition during every boot, so make sure the | |
326 | underlying block device is specified correctly.</para></listitem> | |
45ae1a05 LP |
327 | </varlistentry> |
328 | ||
329 | <varlistentry> | |
8cf3ca80 | 330 | <term><varname>tries=</varname></term> |
45ae1a05 | 331 | |
8cf3ca80 JJ |
332 | <listitem><para>Specifies the maximum number of |
333 | times the user is queried for a password.</para></listitem> | |
45ae1a05 LP |
334 | </varlistentry> |
335 | ||
336 | <varlistentry> | |
8cf3ca80 | 337 | <term><varname>verify</varname></term> |
45ae1a05 | 338 | |
8cf3ca80 JJ |
339 | <listitem><para> If the encryption password is |
340 | read from console, it has to be entered twice to | |
341 | prevent typos.</para></listitem> | |
45ae1a05 | 342 | </varlistentry> |
8cf3ca80 | 343 | |
45ae1a05 LP |
344 | </variablelist> |
345 | ||
8e129f51 | 346 | <para>At early boot and when the system manager |
409dee2e | 347 | configuration is reloaded, this file is translated into |
8e129f51 LP |
348 | native systemd units |
349 | by <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para> | |
45ae1a05 LP |
350 | </refsect1> |
351 | ||
352 | <refsect1> | |
353 | <title>Example</title> | |
354 | <example> | |
355 | <title>/etc/crypttab example</title> | |
8cf3ca80 JJ |
356 | <para>Set up four encrypted block devices. One using |
357 | LUKS for normal storage, another one for usage as a swap | |
358 | device and two TrueCrypt volumes.</para> | |
359 | ||
360 | <programlisting>luks UUID=2505567a-9e27-4efe-a4d5-15ad146c258b | |
361 | swap /dev/sda7 /dev/urandom swap | |
362 | truecrypt /dev/sda2 /etc/container_password tcrypt | |
363 | hidden /mnt/tc_hidden /null tcrypt-hidden,tcrypt-keyfile=/etc/keyfile</programlisting> | |
45ae1a05 LP |
364 | </example> |
365 | </refsect1> | |
366 | ||
367 | <refsect1> | |
368 | <title>See Also</title> | |
369 | <para> | |
370 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
371 | <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
8e129f51 | 372 | <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
45ae1a05 LP |
373 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
374 | <citerefentry><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
375 | <citerefentry><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
376 | </para> | |
377 | </refsect1> | |
378 | ||
379 | </refentry> |