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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 | 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 | |
78 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
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 | |
96 | interpreted as a absolute path to a file containing the encryption | |
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 | |
120 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
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 | |
132 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
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 | |
143 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
144 | for possible values and the default value of this | |
145 | option.</para></listitem> | |
146 | </varlistentry> | |
147 | ||
148 | <varlistentry> | |
149 | <term><option>keyfile-offset=</option></term> | |
150 | ||
151 | <listitem><para>Specifies the number of bytes to skip at the | |
152 | start of the key file. See | |
153 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
154 | for possible values and the default value of this | |
155 | option.</para></listitem> | |
156 | </varlistentry> | |
157 | ||
158 | <varlistentry> | |
159 | <term><option>keyfile-size=</option></term> | |
160 | ||
161 | <listitem><para>Specifies the maximum number of bytes to read | |
162 | from the key file. See | |
163 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
164 | for possible values and the default value of this option. This | |
165 | option is ignored in plain encryption mode, as the key file | |
166 | size is then given by the key size.</para></listitem> | |
167 | </varlistentry> | |
168 | ||
169 | <varlistentry> | |
170 | <term><option>key-slot=</option></term> | |
171 | ||
172 | <listitem><para>Specifies the key slot to compare the | |
173 | passphrase or key against. If the key slot does not match the | |
174 | given passphrase or key, but another would, the setup of the | |
175 | device will fail regardless. This option implies | |
176 | <option>luks</option>. See | |
177 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
178 | for possible values. The default is to try all key slots in | |
179 | sequential order.</para></listitem> | |
180 | </varlistentry> | |
181 | ||
182 | <varlistentry> | |
183 | <term><option>luks</option></term> | |
184 | ||
185 | <listitem><para>Force LUKS mode. When this mode is used, the | |
186 | following options are ignored since they are provided by the | |
187 | LUKS header on the device: <option>cipher=</option>, | |
188 | <option>hash=</option>, | |
189 | <option>size=</option>.</para></listitem> | |
190 | </varlistentry> | |
191 | ||
192 | <varlistentry> | |
193 | <term><option>noauto</option></term> | |
194 | ||
195 | <listitem><para>This device will not be automatically unlocked | |
196 | on boot.</para></listitem> | |
197 | </varlistentry> | |
198 | ||
199 | <varlistentry> | |
200 | <term><option>nofail</option></term> | |
201 | ||
202 | <listitem><para>The system will not wait for the device to | |
203 | show up and be unlocked at boot, and not fail the boot if it | |
204 | does not show up.</para></listitem> | |
205 | </varlistentry> | |
206 | ||
207 | <varlistentry> | |
208 | <term><option>plain</option></term> | |
209 | ||
210 | <listitem><para>Force plain encryption mode.</para></listitem> | |
211 | </varlistentry> | |
212 | ||
213 | <varlistentry> | |
214 | <term><option>read-only</option></term><term><option>readonly</option></term> | |
215 | ||
216 | <listitem><para>Set up the encrypted block device in read-only | |
217 | mode.</para></listitem> | |
218 | </varlistentry> | |
219 | ||
220 | <varlistentry> | |
221 | <term><option>size=</option></term> | |
222 | ||
223 | <listitem><para>Specifies the key size in bits. See | |
224 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
225 | for possible values and the default value of this | |
226 | option.</para></listitem> | |
227 | </varlistentry> | |
228 | ||
229 | <varlistentry> | |
230 | <term><option>swap</option></term> | |
231 | ||
232 | <listitem><para>The encrypted block device will be used as a | |
233 | swap device, and will be formatted accordingly after setting | |
234 | up the encrypted block device, with | |
235 | <citerefentry project='man-pages'><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
236 | This option implies <option>plain</option>.</para> | |
237 | ||
238 | <para>WARNING: Using the <option>swap</option> option will | |
239 | destroy the contents of the named partition during every boot, | |
240 | so make sure the underlying block device is specified | |
241 | correctly.</para></listitem> | |
242 | </varlistentry> | |
243 | ||
244 | <varlistentry> | |
245 | <term><option>tcrypt</option></term> | |
246 | ||
247 | <listitem><para>Use TrueCrypt encryption mode. When this mode | |
248 | is used, the following options are ignored since they are | |
249 | provided by the TrueCrypt header on the device or do not | |
250 | apply: | |
251 | <option>cipher=</option>, | |
252 | <option>hash=</option>, | |
253 | <option>keyfile-offset=</option>, | |
254 | <option>keyfile-size=</option>, | |
255 | <option>size=</option>.</para> | |
256 | ||
257 | <para>When this mode is used, the passphrase is read from the | |
258 | key file given in the third field. Only the first line of this | |
259 | file is read, excluding the new line character.</para> | |
260 | ||
261 | <para>Note that the TrueCrypt format uses both passphrase and | |
262 | key files to derive a password for the volume. Therefore, the | |
263 | passphrase and all key files need to be provided. Use | |
264 | <option>tcrypt-keyfile=</option> to provide the absolute path | |
265 | to all key files. When using an empty passphrase in | |
266 | combination with one or more key files, use | |
267 | <literal>/dev/null</literal> as the password file in the third | |
268 | field.</para></listitem> | |
269 | </varlistentry> | |
270 | ||
271 | <varlistentry> | |
272 | <term><option>tcrypt-hidden</option></term> | |
273 | ||
274 | <listitem><para>Use the hidden TrueCrypt volume. This option | |
275 | implies <option>tcrypt</option>.</para> | |
276 | ||
277 | <para>This will map the hidden volume that is inside of the | |
278 | volume provided in the second field. Please note that there is | |
279 | no protection for the hidden volume if the outer volume is | |
280 | mounted instead. See | |
281 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
282 | for more information on this limitation.</para></listitem> | |
283 | </varlistentry> | |
284 | ||
285 | <varlistentry> | |
286 | <term><option>tcrypt-keyfile=</option></term> | |
287 | ||
288 | <listitem><para>Specifies the absolute path to a key file to | |
289 | use for a TrueCrypt volume. This implies | |
290 | <option>tcrypt</option> and can be used more than once to | |
291 | provide several key files.</para> | |
292 | ||
293 | <para>See the entry for <option>tcrypt</option> on the | |
294 | behavior of the passphrase and key files when using TrueCrypt | |
295 | encryption mode.</para></listitem> | |
296 | </varlistentry> | |
297 | ||
298 | <varlistentry> | |
299 | <term><option>tcrypt-system</option></term> | |
300 | ||
301 | <listitem><para>Use TrueCrypt in system encryption mode. This | |
302 | option implies <option>tcrypt</option>.</para></listitem> | |
303 | </varlistentry> | |
304 | ||
305 | <varlistentry> | |
306 | <term><option>timeout=</option></term> | |
307 | ||
308 | <listitem><para>Specifies the timeout for querying for a | |
309 | password. If no unit is specified, seconds is used. Supported | |
310 | units are s, ms, us, min, h, d. A timeout of 0 waits | |
311 | indefinitely (which is the default).</para></listitem> | |
312 | </varlistentry> | |
313 | ||
314 | <varlistentry> | |
315 | <term><option>x-systemd.device-timeout=</option></term> | |
316 | ||
317 | <listitem><para>Specifies how long systemd should wait for a | |
318 | device to show up before giving up on the entry. The argument | |
319 | is a time in seconds or explicitly specified units of | |
320 | <literal>s</literal>, | |
321 | <literal>min</literal>, | |
322 | <literal>h</literal>, | |
323 | <literal>ms</literal>. | |
324 | </para></listitem> | |
325 | </varlistentry> | |
326 | ||
327 | <varlistentry> | |
328 | <term><option>tmp</option></term> | |
329 | ||
330 | <listitem><para>The encrypted block device will be prepared | |
331 | for using it as <filename>/tmp</filename>; it will be | |
332 | formatted using | |
333 | <citerefentry project='man-pages'><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>. | |
334 | This option implies <option>plain</option>.</para> | |
335 | ||
336 | <para>WARNING: Using the <option>tmp</option> option will | |
337 | destroy the contents of the named partition during every boot, | |
338 | so make sure the underlying block device is specified | |
339 | correctly.</para></listitem> | |
340 | </varlistentry> | |
341 | ||
342 | <varlistentry> | |
343 | <term><option>tries=</option></term> | |
344 | ||
345 | <listitem><para>Specifies the maximum number of times the user | |
346 | is queried for a password. The default is 3. If set to 0, the | |
347 | user is queried for a password indefinitely.</para></listitem> | |
348 | </varlistentry> | |
349 | ||
350 | <varlistentry> | |
351 | <term><option>verify</option></term> | |
352 | ||
353 | <listitem><para> If the encryption password is read from | |
354 | console, it has to be entered twice to prevent | |
355 | typos.</para></listitem> | |
356 | </varlistentry> | |
357 | ||
358 | </variablelist> | |
359 | ||
360 | <para>At early boot and when the system manager configuration is | |
361 | reloaded, this file is translated into native systemd units by | |
362 | <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para> | |
363 | </refsect1> | |
364 | ||
365 | <refsect1> | |
366 | <title>Example</title> | |
367 | <example> | |
368 | <title>/etc/crypttab example</title> | |
369 | <para>Set up four encrypted block devices. One using LUKS for | |
370 | normal storage, another one for usage as a swap device and two | |
371 | TrueCrypt volumes.</para> | |
372 | ||
373 | <programlisting>luks UUID=2505567a-9e27-4efe-a4d5-15ad146c258b | |
374 | swap /dev/sda7 /dev/urandom swap | |
8cf3ca80 | 375 | truecrypt /dev/sda2 /etc/container_password tcrypt |
798d3a52 ZJS |
376 | hidden /mnt/tc_hidden /dev/null tcrypt-hidden,tcrypt-keyfile=/etc/keyfile</programlisting> |
377 | </example> | |
378 | </refsect1> | |
379 | ||
380 | <refsect1> | |
381 | <title>See Also</title> | |
382 | <para> | |
383 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
384 | <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
385 | <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
386 | <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
387 | <citerefentry project='man-pages'><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>, | |
388 | <citerefentry project='man-pages'><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
389 | </para> | |
390 | </refsect1> | |
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391 | |
392 | </refentry> |