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b36b082c | 1 | <?xml version='1.0'?> <!--*-nxml-*--> |
3a54a157 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
0307f791 | 4 | <!-- SPDX-License-Identifier: LGPL-2.1+ --> |
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5 | |
6 | <refentry id="systemd.path"> | |
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7 | <refentryinfo> |
8 | <title>systemd.path</title> | |
9 | <productname>systemd</productname> | |
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10 | </refentryinfo> |
11 | ||
12 | <refmeta> | |
13 | <refentrytitle>systemd.path</refentrytitle> | |
14 | <manvolnum>5</manvolnum> | |
15 | </refmeta> | |
16 | ||
17 | <refnamediv> | |
18 | <refname>systemd.path</refname> | |
19 | <refpurpose>Path unit configuration</refpurpose> | |
20 | </refnamediv> | |
21 | ||
22 | <refsynopsisdiv> | |
23 | <para><filename><replaceable>path</replaceable>.path</filename></para> | |
24 | </refsynopsisdiv> | |
25 | ||
26 | <refsect1> | |
27 | <title>Description</title> | |
28 | ||
29 | <para>A unit configuration file whose name ends in | |
30 | <literal>.path</literal> encodes information about a path | |
31 | monitored by systemd, for path-based activation.</para> | |
32 | ||
33 | <para>This man page lists the configuration options specific to | |
34 | this unit type. See | |
35 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> | |
36 | for the common options of all unit configuration files. The common | |
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37 | configuration items are configured in the generic <literal>[Unit]</literal> and |
38 | <literal>[Install]</literal> sections. The path specific configuration options are | |
39 | configured in the <literal>[Path]</literal> section.</para> | |
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40 | |
41 | <para>For each path file, a matching unit file must exist, | |
42 | describing the unit to activate when the path changes. By default, | |
43 | a service by the same name as the path (except for the suffix) is | |
44 | activated. Example: a path file <filename>foo.path</filename> | |
45 | activates a matching service <filename>foo.service</filename>. The | |
46 | unit to activate may be controlled by <varname>Unit=</varname> | |
47 | (see below).</para> | |
48 | ||
49 | <para>Internally, path units use the | |
3ba3a79d | 50 | <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
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51 | API to monitor file systems. Due to that, it suffers by the same |
52 | limitations as inotify, and for example cannot be used to monitor | |
53 | files or directories changed by other machines on remote NFS file | |
54 | systems.</para> | |
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55 | |
56 | <para>When a service unit triggered by a path unit terminates (regardless whether it exited successfully | |
57 | or failed), monitored paths are checked immediately again, and the service accordingly restarted | |
58 | instantly. As protection against busy looping in this trigger/start cycle, a start rate limit is enforced | |
59 | on the service unit, see <varname>StartLimitIntervalSec=</varname> and | |
60 | <varname>StartLimitBurst=</varname> in | |
61 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Unlike | |
62 | other service failures, the error condition that the start rate limit is hit is propagated from the | |
63 | service unit to the path unit and causes the path unit to fail as well, thus ending the loop.</para> | |
c129bd5d | 64 | </refsect1> |
798d3a52 | 65 | |
c129bd5d | 66 | <refsect1> |
aed5cb03 | 67 | <title>Automatic Dependencies</title> |
45f09f93 | 68 | |
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69 | <refsect2> |
70 | <title>Implicit Dependencies</title> | |
45f09f93 | 71 | |
aed5cb03 | 72 | <para>The following dependencies are implicitly added:</para> |
45f09f93 | 73 | |
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74 | <itemizedlist> |
75 | <listitem><para>If a path unit is beneath another mount unit in the file | |
76 | system hierarchy, both a requirement and an ordering dependency | |
77 | between both units are created automatically.</para></listitem> | |
45f09f93 | 78 | |
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79 | <listitem><para>An implicit <varname>Before=</varname> dependency is added |
80 | between a path unit and the unit it is supposed to activate.</para></listitem> | |
81 | </itemizedlist> | |
82 | </refsect2> | |
83 | ||
84 | <refsect2> | |
85 | <title>Default Dependencies</title> | |
45f09f93 | 86 | |
aed5cb03 | 87 | <para>The following dependencies are added unless <varname>DefaultDependencies=no</varname> is set:</para> |
45f09f93 | 88 | |
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89 | <itemizedlist> |
90 | <listitem><para>Path units will automatically have dependencies of type <varname>Before=</varname> on | |
91 | <filename>paths.target</filename>, | |
92 | dependencies of type <varname>After=</varname> and <varname>Requires=</varname> on | |
93 | <filename>sysinit.target</filename>, and have dependencies of type <varname>Conflicts=</varname> and | |
94 | <varname>Before=</varname> on <filename>shutdown.target</filename>. These ensure that path units are terminated | |
95 | cleanly prior to system shutdown. Only path units involved with early boot or late system shutdown should | |
96 | disable <varname>DefaultDependencies=</varname> option.</para></listitem> | |
97 | </itemizedlist> | |
45f09f93 | 98 | |
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99 | <para></para> |
100 | </refsect2> | |
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101 | </refsect1> |
102 | ||
103 | <refsect1> | |
104 | <title>Options</title> | |
105 | ||
106 | <para>Path files must include a [Path] section, which carries | |
107 | information about the path(s) it monitors. The options specific to | |
108 | the [Path] section of path units are the following:</para> | |
109 | ||
110 | <variablelist class='unit-directives'> | |
111 | <varlistentry> | |
112 | <term><varname>PathExists=</varname></term> | |
113 | <term><varname>PathExistsGlob=</varname></term> | |
114 | <term><varname>PathChanged=</varname></term> | |
115 | <term><varname>PathModified=</varname></term> | |
116 | <term><varname>DirectoryNotEmpty=</varname></term> | |
117 | ||
118 | <listitem><para>Defines paths to monitor for certain changes: | |
119 | <varname>PathExists=</varname> may be used to watch the mere | |
120 | existence of a file or directory. If the file specified | |
121 | exists, the configured unit is activated. | |
122 | <varname>PathExistsGlob=</varname> works similar, but checks | |
123 | for the existence of at least one file matching the globbing | |
124 | pattern specified. <varname>PathChanged=</varname> may be used | |
125 | to watch a file or directory and activate the configured unit | |
126 | whenever it changes. It is not activated on every write to the | |
127 | watched file but it is activated if the file which was open | |
128 | for writing gets closed. <varname>PathModified=</varname> is | |
129 | similar, but additionally it is activated also on simple | |
130 | writes to the watched file. | |
131 | <varname>DirectoryNotEmpty=</varname> may be used to watch a | |
132 | directory and activate the configured unit whenever it | |
133 | contains at least one file.</para> | |
134 | ||
135 | <para>The arguments of these directives must be absolute file | |
136 | system paths.</para> | |
137 | ||
138 | <para>Multiple directives may be combined, of the same and of | |
139 | different types, to watch multiple paths. If the empty string | |
140 | is assigned to any of these options, the list of paths to | |
141 | watch is reset, and any prior assignments of these options | |
142 | will not have any effect.</para> | |
143 | ||
144 | <para>If a path already exists (in case of | |
145 | <varname>PathExists=</varname> and | |
146 | <varname>PathExistsGlob=</varname>) or a directory already is | |
147 | not empty (in case of <varname>DirectoryNotEmpty=</varname>) | |
148 | at the time the path unit is activated, then the configured | |
149 | unit is immediately activated as well. Something similar does | |
150 | not apply to <varname>PathChanged=</varname> and | |
151 | <varname>PathModified=</varname>.</para> | |
152 | ||
153 | <para>If the path itself or any of the containing directories | |
154 | are not accessible, <command>systemd</command> will watch for | |
155 | permission changes and notice that conditions are satisfied | |
156 | when permissions allow that. </para></listitem> | |
157 | </varlistentry> | |
158 | <varlistentry> | |
159 | <term><varname>Unit=</varname></term> | |
160 | ||
161 | <listitem><para>The unit to activate when any of the | |
162 | configured paths changes. The argument is a unit name, whose | |
163 | suffix is not <literal>.path</literal>. If not specified, this | |
164 | value defaults to a service that has the same name as the path | |
165 | unit, except for the suffix. (See above.) It is recommended | |
166 | that the unit name that is activated and the unit name of the | |
167 | path unit are named identical, except for the | |
168 | suffix.</para></listitem> | |
169 | </varlistentry> | |
170 | <varlistentry> | |
171 | <term><varname>MakeDirectory=</varname></term> | |
172 | ||
173 | <listitem><para>Takes a boolean argument. If true, the | |
174 | directories to watch are created before watching. This option | |
175 | is ignored for <varname>PathExists=</varname> settings. | |
176 | Defaults to <option>false</option>.</para></listitem> | |
177 | </varlistentry> | |
178 | <varlistentry> | |
179 | <term><varname>DirectoryMode=</varname></term> | |
180 | ||
181 | <listitem><para>If <varname>MakeDirectory=</varname> is | |
182 | enabled, use the mode specified here to create the directories | |
183 | in question. Takes an access mode in octal notation. Defaults | |
184 | to <option>0755</option>.</para></listitem> | |
185 | </varlistentry> | |
186 | </variablelist> | |
187 | </refsect1> | |
188 | ||
189 | <refsect1> | |
190 | <title>See Also</title> | |
191 | <para> | |
192 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
193 | <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
194 | <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
195 | <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>, | |
3ba3a79d | 196 | <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>, |
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197 | <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
198 | </para> | |
199 | </refsect1> | |
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200 | |
201 | </refentry> |