man/systemd.path.xml

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  23
  24 <refentry id="systemd.path">
  25   <refentryinfo>
  26     <title>systemd.path</title>
  27     <productname>systemd</productname>
  28
  29     <authorgroup>
  30       <author>
  31         <contrib>Developer</contrib>
  32         <firstname>Lennart</firstname>
  33         <surname>Poettering</surname>
  34         <email>lennart@poettering.net</email>
  35       </author>
  36     </authorgroup>
  37   </refentryinfo>
  38
  39   <refmeta>
  40     <refentrytitle>systemd.path</refentrytitle>
  41     <manvolnum>5</manvolnum>
  42   </refmeta>
  43
  44   <refnamediv>
  45     <refname>systemd.path</refname>
  46     <refpurpose>Path unit configuration</refpurpose>
  47   </refnamediv>
  48
  49   <refsynopsisdiv>
  50     <para><filename><replaceable>path</replaceable>.path</filename></para>
  51   </refsynopsisdiv>
  52
  53   <refsect1>
  54     <title>Description</title>
  55
  56     <para>A unit configuration file whose name ends in
  57     <literal>.path</literal> encodes information about a path
  58     monitored by systemd, for path-based activation.</para>
  59
  60     <para>This man page lists the configuration options specific to
  61     this unit type. See
  62     <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  63     for the common options of all unit configuration files. The common
  64     configuration items are configured in the generic [Unit] and
  65     [Install] sections. The path specific configuration options are
  66     configured in the [Path] section.</para>
  67
  68     <para>For each path file, a matching unit file must exist,
  69     describing the unit to activate when the path changes. By default,
  70     a service by the same name as the path (except for the suffix) is
  71     activated. Example: a path file <filename>foo.path</filename>
  72     activates a matching service <filename>foo.service</filename>. The
  73     unit to activate may be controlled by <varname>Unit=</varname>
  74     (see below).</para>
  75
  76     <para>Internally, path units use the
  77     <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  78     API to monitor file systems. Due to that, it suffers by the same
  79     limitations as inotify, and for example cannot be used to monitor
  80     files or directories changed by other machines on remote NFS file
  81     systems.</para>
  82   </refsect1>
  83
  84   <refsect1>
  85     <title>Implicit Dependencies</title>
  86
  87     <para>The following dependencies are implicitly added:</para>
  88
  89     <itemizedlist>
  90       <listitem><para>If a path unit is beneath another mount unit in the file
  91       system hierarchy, both a requirement and an ordering dependency
  92       between both units are created automatically.</para></listitem>
  93
  94       <listitem><para>An implicit <varname>Before=</varname> dependency is added
  95       between a path unit and the unit it is supposed to activate.</para></listitem>
  96     </itemizedlist>
  97   </refsect1>
  98
  99   <refsect1>
 100     <title>Default Dependencies</title>
 101
 102     <para>The following dependencies are added unless <varname>DefaultDependencies=no</varname> is set:</para>
 103
 104     <itemizedlist>
 105       <listitem><para>Path units will automatically have dependencies of type <varname>Before=</varname> on
 106       <filename>paths.target</filename>,
 107       dependencies of type <varname>After=</varname> and <varname>Requires=</varname> on
 108       <filename>sysinit.target</filename>, and have dependencies of type <varname>Conflicts=</varname> and
 109       <varname>Before=</varname> on <filename>shutdown.target</filename>. These ensure that path units are terminated
 110       cleanly prior to system shutdown. Only path units involved with early boot or late system shutdown should
 111       disable <varname>DefaultDependencies=</varname> option.</para></listitem>
 112     </itemizedlist>
 113
 114     <para></para>
 115   </refsect1>
 116
 117   <refsect1>
 118     <title>Options</title>
 119
 120     <para>Path files must include a [Path] section, which carries
 121     information about the path(s) it monitors. The options specific to
 122     the [Path] section of path units are the following:</para>
 123
 124     <variablelist class='unit-directives'>
 125       <varlistentry>
 126         <term><varname>PathExists=</varname></term>
 127         <term><varname>PathExistsGlob=</varname></term>
 128         <term><varname>PathChanged=</varname></term>
 129         <term><varname>PathModified=</varname></term>
 130         <term><varname>DirectoryNotEmpty=</varname></term>
 131
 132         <listitem><para>Defines paths to monitor for certain changes:
 133         <varname>PathExists=</varname> may be used to watch the mere
 134         existence of a file or directory. If the file specified
 135         exists, the configured unit is activated.
 136         <varname>PathExistsGlob=</varname> works similar, but checks
 137         for the existence of at least one file matching the globbing
 138         pattern specified. <varname>PathChanged=</varname> may be used
 139         to watch a file or directory and activate the configured unit
 140         whenever it changes. It is not activated on every write to the
 141         watched file but it is activated if the file which was open
 142         for writing gets closed. <varname>PathModified=</varname> is
 143         similar, but additionally it is activated also on simple
 144         writes to the watched file.
 145         <varname>DirectoryNotEmpty=</varname> may be used to watch a
 146         directory and activate the configured unit whenever it
 147         contains at least one file.</para>
 148
 149         <para>The arguments of these directives must be absolute file
 150         system paths.</para>
 151
 152         <para>Multiple directives may be combined, of the same and of
 153         different types, to watch multiple paths. If the empty string
 154         is assigned to any of these options, the list of paths to
 155         watch is reset, and any prior assignments of these options
 156         will not have any effect.</para>
 157
 158         <para>If a path already exists (in case of
 159         <varname>PathExists=</varname> and
 160         <varname>PathExistsGlob=</varname>) or a directory already is
 161         not empty (in case of <varname>DirectoryNotEmpty=</varname>)
 162         at the time the path unit is activated, then the configured
 163         unit is immediately activated as well. Something similar does
 164         not apply to <varname>PathChanged=</varname> and
 165         <varname>PathModified=</varname>.</para>
 166
 167         <para>If the path itself or any of the containing directories
 168         are not accessible, <command>systemd</command> will watch for
 169         permission changes and notice that conditions are satisfied
 170         when permissions allow that. </para></listitem>
 171       </varlistentry>
 172       <varlistentry>
 173         <term><varname>Unit=</varname></term>
 174
 175         <listitem><para>The unit to activate when any of the
 176         configured paths changes. The argument is a unit name, whose
 177         suffix is not <literal>.path</literal>. If not specified, this
 178         value defaults to a service that has the same name as the path
 179         unit, except for the suffix. (See above.) It is recommended
 180         that the unit name that is activated and the unit name of the
 181         path unit are named identical, except for the
 182         suffix.</para></listitem>
 183       </varlistentry>
 184       <varlistentry>
 185         <term><varname>MakeDirectory=</varname></term>
 186
 187         <listitem><para>Takes a boolean argument. If true, the
 188         directories to watch are created before watching. This option
 189         is ignored for <varname>PathExists=</varname> settings.
 190         Defaults to <option>false</option>.</para></listitem>
 191       </varlistentry>
 192       <varlistentry>
 193         <term><varname>DirectoryMode=</varname></term>
 194
 195         <listitem><para>If <varname>MakeDirectory=</varname> is
 196         enabled, use the mode specified here to create the directories
 197         in question. Takes an access mode in octal notation. Defaults
 198         to <option>0755</option>.</para></listitem>
 199       </varlistentry>
 200     </variablelist>
 201   </refsect1>
 202
 203   <refsect1>
 204       <title>See Also</title>
 205       <para>
 206         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 207         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 208         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 209         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 210         <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 211         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 212       </para>
 213   </refsect1>
 214
 215 </refentry>