1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
|
<?xml version="1.0"?>
<!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2012 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
This is based on crypttab(5) from Fedora's initscripts package, which in
turn is based on Debian's version.
The Red Hat version has been written by Miloslav Trmac <mitr@redhat.com>.
-->
<refentry id="crypttab" conditional='HAVE_LIBCRYPTSETUP'>
<refentryinfo>
<title>crypttab</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Documentation</contrib>
<firstname>Miloslav</firstname>
<surname>Trmac</surname>
<email>mitr@redhat.com</email>
</author>
<author>
<contrib>Documentation</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>crypttab</refentrytitle>
<manvolnum>5</manvolnum>
</refmeta>
<refnamediv>
<refname>crypttab</refname>
<refpurpose>Configuration for encrypted block devices</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>/etc/crypttab</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>The <filename>/etc/crypttab</filename> file
describes encrypted block devices that are set up
during system boot.</para>
<para>Empty lines and lines starting with the <literal>#</literal>
character are ignored. Each of the remaining lines
describes one encrypted block device, fields on the
line are delimited by white space. The first two
fields are mandatory, the remaining two are
optional.</para>
<para>The first field contains the name of the
resulting encrypted block device; the device is set up
within <filename>/dev/mapper/</filename>.</para>
<para>The second field contains a path to the
underlying block device, or a specification of a block
device via <literal>UUID=</literal> followed by the
UUID. If the block device contains a LUKS signature,
it is opened as a LUKS encrypted partition; otherwise,
it is assumed to be a raw dm-crypt partition.</para>
<para>The third field specifies the encryption
password. If the field is not present or the password
is set to none, the password has to be manually
entered during system boot. Otherwise, the field is
interpreted as a path to a file containing the
encryption password. For swap encryption,
<filename>/dev/urandom</filename> or the hardware
device <filename>/dev/hw_random</filename> can be used
as the password file; using
<filename>/dev/random</filename> may prevent boot
completion if the system does not have enough entropy
to generate a truly random encryption key.</para>
<para>The fourth field, if present, is a
comma-delimited list of options. The following
options are recognized:</para>
<variablelist class='crypttab-options'>
<varlistentry>
<term><varname>cipher=</varname></term>
<listitem><para>Specifies the cipher
to use; see
<citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for possible values and the default
value of this option. A cipher with
unpredictable IV values, such as
<literal>aes-cbc-essiv:sha256</literal>,
is recommended. </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>size=</varname></term>
<listitem><para>Specifies the key size
in bits; see
<citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for possible values and the default
value of this
option. </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>keyfile-size=</varname></term>
<listitem><para>Specifies the maximum number
of bytes to read from the keyfile; see
<citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for possible values and the default
value of this option. This option is ignored
in plain encryption mode, as the keyfile-size is then given by the key size.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>keyfile-offset=</varname></term>
<listitem><para>Specifies the number
of bytes to skip at the start of
the keyfile; see
<citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
for possible values and the default
value of this option.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>hash=</varname></term>
<listitem><para>Specifies the hash to
use for password hashing; see
<citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> for possible values and
the default value of this
option. </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>tries=</varname></term>
<listitem><para>Specifies the maximum
number of times the user is queried
for a password.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>verify</varname></term>
<listitem><para> If the encryption
password is read from console, it has
to be entered twice (to prevent
typos). </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>read-only</varname></term><term><varname>readonly</varname></term>
<listitem><para>Set up the encrypted
block device in read-only
mode.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>allow-discards</varname></term>
<listitem><para>Allow discard requests
to be passed through the encrypted
block device. This improves
performance on SSD storage but has
security
implications.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>luks</varname></term>
<listitem><para>Force LUKS mode.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>plain</varname></term>
<listitem><para>Force plain encryption
mode.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>timeout=</varname></term>
<listitem><para>Specify the timeout
for querying for a password. If no
unit is specified seconds is used.
Supported units are s, ms, us, min, h,
d. A timeout of 0 waits indefinitely
(which is the
default).</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>noauto</varname></term>
<listitem><para> This device will not
be automatically unlocked on
boot. </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>nofail</varname></term>
<listitem><para>The system will not
wait for the device to show up and be
unlocked at boot, and not fail the
boot if it does not show
up.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>swap</varname></term>
<listitem><para> The encrypted block
device will be used as a swap
partition, and will be formatted as a
swap partition after setting up the
encrypted block device, with
<citerefentry><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
<para>WARNING: Using the
<varname>swap</varname> option will
destroy the contents of the named
partition during every boot, so make
sure the underlying block device is
specified
correctly. </para></listitem>
</varlistentry>
<varlistentry>
<term><varname>tmp</varname></term>
<listitem><para>The encrypted block
device will be prepared for using it
as <filename>/tmp</filename>
partition: it will be formatted using
<citerefentry><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
<para>WARNING: Using the
<varname>tmp</varname> option will
destroy the contents of the named
partition during every boot, so make
sure the underlying block device is
specified
correctly. </para></listitem>
</varlistentry>
</variablelist>
<para>At early boot and when the system manager
configuration is reloaded, this file is translated into
native systemd units
by <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</refsect1>
<refsect1>
<title>Example</title>
<example>
<title>/etc/crypttab example</title>
<para>Set up two encrypted block devices with
LUKS: one normal one for storage, and another
one for usage as swap device.</para>
<programlisting>luks-2505567a-9e27-4efe-a4d5-15ad146c258b UUID=2505567a-9e27-4efe-a4d5-15ad146c258b - timeout=0
swap /dev/sda7 /dev/urandom swap</programlisting>
</example>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
|
