man/systemd.path.xml

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   5
   6 <refentry id="systemd.path">
   7   <refentryinfo>
   8     <title>systemd.path</title>
   9     <productname>systemd</productname>
  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
  37     configuration items are configured in the generic [Unit] and
  38     [Install] sections. The path specific configuration options are
  39     configured in the [Path] section.</para>
  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
  50     <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  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>
  55   </refsect1>
  56
  57   <refsect1>
  58     <title>Automatic Dependencies</title>
  59
  60     <refsect2>
  61       <title>Implicit Dependencies</title>
  62
  63       <para>The following dependencies are implicitly added:</para>
  64
  65       <itemizedlist>
  66         <listitem><para>If a path unit is beneath another mount unit in the file
  67         system hierarchy, both a requirement and an ordering dependency
  68         between both units are created automatically.</para></listitem>
  69
  70         <listitem><para>An implicit <varname>Before=</varname> dependency is added
  71         between a path unit and the unit it is supposed to activate.</para></listitem>
  72       </itemizedlist>
  73     </refsect2>
  74
  75     <refsect2>
  76       <title>Default Dependencies</title>
  77
  78       <para>The following dependencies are added unless <varname>DefaultDependencies=no</varname> is set:</para>
  79
  80       <itemizedlist>
  81         <listitem><para>Path units will automatically have dependencies of type <varname>Before=</varname> on
  82         <filename>paths.target</filename>,
  83         dependencies of type <varname>After=</varname> and <varname>Requires=</varname> on
  84         <filename>sysinit.target</filename>, and have dependencies of type <varname>Conflicts=</varname> and
  85         <varname>Before=</varname> on <filename>shutdown.target</filename>. These ensure that path units are terminated
  86         cleanly prior to system shutdown. Only path units involved with early boot or late system shutdown should
  87         disable <varname>DefaultDependencies=</varname> option.</para></listitem>
  88       </itemizedlist>
  89
  90       <para></para>
  91     </refsect2>
  92   </refsect1>
  93
  94   <refsect1>
  95     <title>Options</title>
  96
  97     <para>Path files must include a [Path] section, which carries
  98     information about the path(s) it monitors. The options specific to
  99     the [Path] section of path units are the following:</para>
 100
 101     <variablelist class='unit-directives'>
 102       <varlistentry>
 103         <term><varname>PathExists=</varname></term>
 104         <term><varname>PathExistsGlob=</varname></term>
 105         <term><varname>PathChanged=</varname></term>
 106         <term><varname>PathModified=</varname></term>
 107         <term><varname>DirectoryNotEmpty=</varname></term>
 108
 109         <listitem><para>Defines paths to monitor for certain changes:
 110         <varname>PathExists=</varname> may be used to watch the mere
 111         existence of a file or directory. If the file specified
 112         exists, the configured unit is activated.
 113         <varname>PathExistsGlob=</varname> works similar, but checks
 114         for the existence of at least one file matching the globbing
 115         pattern specified. <varname>PathChanged=</varname> may be used
 116         to watch a file or directory and activate the configured unit
 117         whenever it changes. It is not activated on every write to the
 118         watched file but it is activated if the file which was open
 119         for writing gets closed. <varname>PathModified=</varname> is
 120         similar, but additionally it is activated also on simple
 121         writes to the watched file.
 122         <varname>DirectoryNotEmpty=</varname> may be used to watch a
 123         directory and activate the configured unit whenever it
 124         contains at least one file.</para>
 125
 126         <para>The arguments of these directives must be absolute file
 127         system paths.</para>
 128
 129         <para>Multiple directives may be combined, of the same and of
 130         different types, to watch multiple paths. If the empty string
 131         is assigned to any of these options, the list of paths to
 132         watch is reset, and any prior assignments of these options
 133         will not have any effect.</para>
 134
 135         <para>If a path already exists (in case of
 136         <varname>PathExists=</varname> and
 137         <varname>PathExistsGlob=</varname>) or a directory already is
 138         not empty (in case of <varname>DirectoryNotEmpty=</varname>)
 139         at the time the path unit is activated, then the configured
 140         unit is immediately activated as well. Something similar does
 141         not apply to <varname>PathChanged=</varname> and
 142         <varname>PathModified=</varname>.</para>
 143
 144         <para>If the path itself or any of the containing directories
 145         are not accessible, <command>systemd</command> will watch for
 146         permission changes and notice that conditions are satisfied
 147         when permissions allow that. </para></listitem>
 148       </varlistentry>
 149       <varlistentry>
 150         <term><varname>Unit=</varname></term>
 151
 152         <listitem><para>The unit to activate when any of the
 153         configured paths changes. The argument is a unit name, whose
 154         suffix is not <literal>.path</literal>. If not specified, this
 155         value defaults to a service that has the same name as the path
 156         unit, except for the suffix. (See above.) It is recommended
 157         that the unit name that is activated and the unit name of the
 158         path unit are named identical, except for the
 159         suffix.</para></listitem>
 160       </varlistentry>
 161       <varlistentry>
 162         <term><varname>MakeDirectory=</varname></term>
 163
 164         <listitem><para>Takes a boolean argument. If true, the
 165         directories to watch are created before watching. This option
 166         is ignored for <varname>PathExists=</varname> settings.
 167         Defaults to <option>false</option>.</para></listitem>
 168       </varlistentry>
 169       <varlistentry>
 170         <term><varname>DirectoryMode=</varname></term>
 171
 172         <listitem><para>If <varname>MakeDirectory=</varname> is
 173         enabled, use the mode specified here to create the directories
 174         in question. Takes an access mode in octal notation. Defaults
 175         to <option>0755</option>.</para></listitem>
 176       </varlistentry>
 177     </variablelist>
 178   </refsect1>
 179
 180   <refsect1>
 181       <title>See Also</title>
 182       <para>
 183         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 184         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 185         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 186         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 187         <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 188         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 189       </para>
 190   </refsect1>
 191
 192 </refentry>