man/systemd.path.xml

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   9   Copyright 2010 Lennart Poettering
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  24
  25 <refentry id="systemd.path">
  26         <refentryinfo>
  27                 <title>systemd.path</title>
  28                 <productname>systemd</productname>
  29
  30                 <authorgroup>
  31                         <author>
  32                                 <contrib>Developer</contrib>
  33                                 <firstname>Lennart</firstname>
  34                                 <surname>Poettering</surname>
  35                                 <email>lennart@poettering.net</email>
  36                         </author>
  37                 </authorgroup>
  38         </refentryinfo>
  39
  40         <refmeta>
  41                 <refentrytitle>systemd.path</refentrytitle>
  42                 <manvolnum>5</manvolnum>
  43         </refmeta>
  44
  45         <refnamediv>
  46                 <refname>systemd.path</refname>
  47                 <refpurpose>systemd path configuration files</refpurpose>
  48         </refnamediv>
  49
  50         <refsynopsisdiv>
  51                 <para><filename>systemd.path</filename></para>
  52         </refsynopsisdiv>
  53
  54         <refsect1>
  55                 <title>Description</title>
  56
  57                 <para>A unit configuration file whose name ends in
  58                 <filename>.path</filename> encodes information about
  59                 a path monitored by systemd, for
  60                 path-based activation.</para>
  61
  62                 <para>This man page lists the configuration options
  63                 specific to this unit type. See
  64                 <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  65                 for the common options of all unit configuration
  66                 files. The common configuration items are configured
  67                 in the generic [Unit] and [Install] sections. The
  68                 path specific configuration options are configured in
  69                 the [Path] section.</para>
  70
  71                 <para>For each path file, a matching unit file must
  72                 exist, describing the unit to activate when the path
  73                 changes. By default, a service by the same name as the
  74                 path (except for the suffix) is activated. Example: a
  75                 path file <filename>foo.path</filename> activates a
  76                 matching service <filename>foo.service</filename>. The
  77                 unit to activate may be controlled by
  78                 <varname>Unit=</varname> (see below).</para>
  79
  80                 <para>Internally, path units use the
  81                 <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  82                 API to monitor file systems. Due to that, it suffers by the
  83                 same limitations as inotify, and for example cannot be
  84                 used to monitor files or directories changed by other
  85                 machines on remote NFS file systems.</para>
  86
  87                 <para>If an path unit is beneath another mount
  88                 point in the file system hierarchy, a dependency
  89                 between both units is created automatically.</para>
  90
  91                 <para>Unless <varname>DefaultDependencies=</varname>
  92                 is set to <option>false</option>, path units will
  93                 implicitly have dependencies of type
  94                 <varname>Conflicts=</varname> and
  95                 <varname>Before=</varname> on
  96                 <filename>shutdown.target</filename>. These ensure
  97                 that path units are terminated cleanly prior to system
  98                 shutdown. Only path units involved with early boot or
  99                 late system shutdown should disable this
 100                 option.</para>
 101         </refsect1>
 102
 103         <refsect1>
 104                 <title>Options</title>
 105
 106                 <para>Path files must include a [Path] section,
 107                 which carries information about the path(s) it
 108                 monitors. The options specific to the [Path] section
 109                 of path units are the following:</para>
 110
 111                 <variablelist>
 112                         <varlistentry>
 113                                 <term><varname>PathExists=</varname></term>
 114                                 <term><varname>PathChanged=</varname></term>
 115                                 <term><varname>DirectoryNotEmpty=</varname></term>
 116
 117                                 <listitem><para>Defines paths to
 118                                 monitor for certain changes:
 119                                 <varname>PathExists=</varname> may be
 120                                 used to watch the mere existence of a
 121                                 file or directory. If the file
 122                                 specified exists the configured unit
 123                                 is
 124                                 activated. <varname>PathChanged=</varname>
 125                                 may be used to watch a file or
 126                                 directory and activate the configured
 127                                 unit whenever it changes or is
 128                                 modified. <varname>DirectoryNotEmpty=</varname>
 129                                 may be used to watch a directory and
 130                                 activate the configured unit whenever
 131                                 it contains at least one file.</para>
 132
 133                                 <para>The arguments of these
 134                                 directives must be absolute file
 135                                 system paths.</para>
 136
 137                                 <para>Multiple directives may be
 138                                 combined, of the same and of different
 139                                 types, to watch multiple paths.</para>
 140
 141                                 <para>If a path is already existing
 142                                 (in case of
 143                                 <varname>PathExists=</varname>) or a
 144                                 directory already is not empty (in
 145                                 case of
 146                                 <varname>DirectoryNotEmpty=</varname>)
 147                                 at the time the path unit is activated,
 148                                 then the configured unit is
 149                                 immediately activated as
 150                                 well. Something similar does not apply
 151                                 to <varname>PathChanged=</varname>.
 152                                 </para></listitem>
 153                         </varlistentry>
 154                         <varlistentry>
 155                                 <term><varname>Unit=</varname></term>
 156
 157                                 <listitem><para>The unit to activate
 158                                 when any of the configured paths
 159                                 changes. The argument is a unit name,
 160                                 whose suffix is not
 161                                 <filename>.path</filename>. If not
 162                                 specified, this value defaults to a
 163                                 service that has the same name as the
 164                                 path unit, except for the suffix. (See
 165                                 above.) It is recommended that the
 166                                 unit name that is activated and the
 167                                 unit name of the path unit are named
 168                                 identical, except for the
 169                                 suffix.</para></listitem>
 170                         </varlistentry>
 171                 </variablelist>
 172         </refsect1>
 173
 174         <refsect1>
 175                   <title>See Also</title>
 176                   <para>
 177                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 178                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 179                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 180                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 181                           <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 182                   </para>
 183         </refsect1>
 184
 185 </refentry>