man/systemd.path.xml

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