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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"> |
059b37cc | 4 | <!-- |
572eb058 | 5 | SPDX-License-Identifier: LGPL-2.1+ |
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6 | --> |
7 | <refentry id="systemd-fstab-generator"> | |
8 | ||
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9 | <refentryinfo> |
10 | <title>systemd-fstab-generator</title> | |
11 | <productname>systemd</productname> | |
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12 | </refentryinfo> |
13 | ||
14 | <refmeta> | |
15 | <refentrytitle>systemd-fstab-generator</refentrytitle> | |
16 | <manvolnum>8</manvolnum> | |
17 | </refmeta> | |
18 | ||
19 | <refnamediv> | |
20 | <refname>systemd-fstab-generator</refname> | |
21 | <refpurpose>Unit generator for /etc/fstab</refpurpose> | |
22 | </refnamediv> | |
23 | ||
24 | <refsynopsisdiv> | |
12b42c76 | 25 | <para><filename>/usr/lib/systemd/system-generators/systemd-fstab-generator</filename></para> |
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26 | </refsynopsisdiv> |
27 | ||
28 | <refsect1> | |
29 | <title>Description</title> | |
30 | ||
31 | <para><filename>systemd-fstab-generator</filename> is a generator | |
32 | that translates <filename>/etc/fstab</filename> (see | |
3ba3a79d | 33 | <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry> |
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34 | for details) into native systemd units early at boot and when |
35 | configuration of the system manager is reloaded. This will | |
36 | instantiate mount and swap units as necessary.</para> | |
37 | ||
38 | <para>The <varname>passno</varname> field is treated like a simple | |
39 | boolean, and the ordering information is discarded. However, if | |
40 | the root file system is checked, it is checked before all the | |
41 | other file systems.</para> | |
42 | ||
43 | <para>See | |
44 | <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
45 | and | |
46 | <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
47 | for more information about special <filename>/etc/fstab</filename> | |
48 | mount options this generator understands.</para> | |
49 | ||
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50 | <para>One special topic is handling of symbolic links. Historical init |
51 | implementations supported symlinks in <filename>/etc/fstab</filename>. | |
52 | Because mount units will refuse mounts where the target is a symbolic link, | |
53 | this generator will resolve any symlinks as far as possible when processing | |
54 | <filename>/etc/fstab</filename> in order to enhance backwards compatibility. | |
55 | If a symlink target does not exist at the time that this generator runs, it | |
56 | is assumed that the symlink target is the final target of the mount.</para> | |
57 | ||
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58 | <para><filename>systemd-fstab-generator</filename> implements |
59 | <citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> | |
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60 | </refsect1> |
61 | ||
62 | <refsect1> | |
63 | <title>Kernel Command Line</title> | |
64 | ||
65 | <para><filename>systemd-fstab-generator</filename> understands the | |
66 | following kernel command line parameters:</para> | |
67 | ||
68 | <variablelist class='kernel-commandline-options'> | |
69 | ||
70 | <varlistentry> | |
71 | <term><varname>fstab=</varname></term> | |
72 | <term><varname>rd.fstab=</varname></term> | |
73 | ||
74 | <listitem><para>Takes a boolean argument. Defaults to | |
75 | <literal>yes</literal>. If <literal>no</literal>, causes the | |
91214a37 | 76 | generator to ignore any mounts or swap devices configured in |
798d3a52 | 77 | <filename>/etc/fstab</filename>. <varname>rd.fstab=</varname> |
91214a37 | 78 | is honored only by the initial RAM disk (initrd) while |
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79 | <varname>fstab=</varname> is honored by both the main system |
80 | and the initrd.</para></listitem> | |
81 | </varlistentry> | |
91214a37 | 82 | |
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83 | <varlistentry> |
84 | <term><varname>root=</varname></term> | |
85 | ||
86 | <listitem><para>Takes the root filesystem to mount in the | |
87 | initrd. <varname>root=</varname> is honored by the | |
88 | initrd.</para></listitem> | |
89 | </varlistentry> | |
91214a37 | 90 | |
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91 | <varlistentry> |
92 | <term><varname>rootfstype=</varname></term> | |
93 | ||
94 | <listitem><para>Takes the root filesystem type that will be | |
95 | passed to the mount command. <varname>rootfstype=</varname> is | |
96 | honored by the initrd.</para></listitem> | |
97 | </varlistentry> | |
91214a37 | 98 | |
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99 | <varlistentry> |
100 | <term><varname>rootflags=</varname></term> | |
101 | ||
102 | <listitem><para>Takes the root filesystem mount options to | |
103 | use. <varname>rootflags=</varname> is honored by the | |
104 | initrd.</para></listitem> | |
105 | </varlistentry> | |
91214a37 | 106 | |
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107 | <varlistentry> |
108 | <term><varname>mount.usr=</varname></term> | |
109 | ||
110 | <listitem><para>Takes the <filename>/usr</filename> filesystem | |
111 | to be mounted by the initrd. If | |
112 | <varname>mount.usrfstype=</varname> or | |
113 | <varname>mount.usrflags=</varname> is set, then | |
114 | <varname>mount.usr=</varname> will default to the value set in | |
115 | <varname>root=</varname>.</para> | |
116 | ||
b938cb90 | 117 | <para>Otherwise, this parameter defaults to the |
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118 | <filename>/usr</filename> entry found in |
119 | <filename>/etc/fstab</filename> on the root filesystem.</para> | |
120 | ||
121 | <para><varname>mount.usr=</varname> is honored by the initrd. | |
122 | </para></listitem> | |
123 | </varlistentry> | |
91214a37 | 124 | |
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125 | <varlistentry> |
126 | <term><varname>mount.usrfstype=</varname></term> | |
127 | ||
128 | <listitem><para>Takes the <filename>/usr</filename> filesystem | |
129 | type that will be passed to the mount command. If | |
130 | <varname>mount.usr=</varname> or | |
131 | <varname>mount.usrflags=</varname> is set, then | |
132 | <varname>mount.usrfstype=</varname> will default to the value | |
133 | set in <varname>rootfstype=</varname>.</para> | |
134 | ||
b938cb90 | 135 | <para>Otherwise, this value will be read from the |
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136 | <filename>/usr</filename> entry in |
137 | <filename>/etc/fstab</filename> on the root filesystem.</para> | |
138 | ||
139 | <para><varname>mount.usrfstype=</varname> is honored by the | |
140 | initrd.</para></listitem> | |
141 | </varlistentry> | |
91214a37 | 142 | |
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143 | <varlistentry> |
144 | <term><varname>mount.usrflags=</varname></term> | |
145 | ||
146 | <listitem><para>Takes the <filename>/usr</filename> filesystem | |
147 | mount options to use. If <varname>mount.usr=</varname> or | |
148 | <varname>mount.usrfstype=</varname> is set, then | |
ff9b60f3 | 149 | <varname>mount.usrflags=</varname> will default to the value |
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150 | set in <varname>rootflags=</varname>.</para> |
151 | ||
b938cb90 | 152 | <para>Otherwise, this value will be read from the |
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153 | <filename>/usr</filename> entry in |
154 | <filename>/etc/fstab</filename> on the root filesystem.</para> | |
155 | ||
156 | <para><varname>mount.usrflags=</varname> is honored by the | |
157 | initrd.</para></listitem> | |
158 | </varlistentry> | |
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159 | |
160 | <varlistentry> | |
161 | <term><varname>systemd.volatile=</varname></term> | |
162 | ||
163 | <listitem><para>Controls whether the system shall boot up in volatile mode. Takes a boolean argument or the | |
164 | special value <option>state</option>.</para> | |
165 | ||
166 | <para>If false (the default), this generator makes no changes to the mount tree and the system is booted up in | |
167 | normal mode.</para> | |
168 | ||
169 | <para>If true the generator ensures | |
170 | <citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> | |
171 | is run as part of the initial RAM disk ("initrd"). This service changes the mount table before transitioning to | |
172 | the host system, so that a volatile memory file system (<literal>tmpfs</literal>) is used as root directory, | |
173 | with only <filename>/usr</filename> mounted into it from the configured root file system, in read-only | |
174 | mode. This way the system operates in fully stateless mode, with all configuration and state reset at boot and | |
175 | lost at shutdown, as <filename>/etc</filename> and <filename>/var</filename> will be served from the (initially | |
176 | unpopulated) volatile memory file system.</para> | |
177 | ||
178 | <para>If set to <option>state</option> the generator will leave the root | |
179 | directory mount point unaltered, however will mount a <literal>tmpfs</literal> file system to | |
301a21a8 | 180 | <filename>/var</filename>. In this mode the normal system configuration (i.e. the contents of |
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181 | <literal>/etc</literal>) is in effect (and may be modified during system runtime), however the system state |
182 | (i.e. the contents of <literal>/var</literal>) is reset at boot and lost at shutdown.</para> | |
183 | ||
184 | <para>Note that in none of these modes the root directory, <filename>/etc</filename>, <filename>/var</filename> | |
185 | or any other resources stored in the root file system are physically removed. It's thus safe to boot a system | |
186 | that is normally operated in non-volatile mode temporarily into volatile mode, without losing data.</para> | |
187 | ||
188 | <para>Note that enabling this setting will only work correctly on operating systems that can boot up with only | |
189 | <filename>/usr</filename> mounted, and are able to automatically populate <filename>/etc</filename>, and also | |
190 | <filename>/var</filename> in case of <literal>systemd.volatile=yes</literal>.</para></listitem> | |
191 | </varlistentry> | |
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192 | </variablelist> |
193 | </refsect1> | |
194 | ||
195 | <refsect1> | |
196 | <title>See Also</title> | |
197 | <para> | |
198 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
3ba3a79d | 199 | <citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
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200 | <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
201 | <citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
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202 | <citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>, |
203 | <citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry> | |
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204 | </para> |
205 | </refsect1> | |
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206 | |
207 | </refentry> |