man/systemd.path.xml

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  11   Copyright 2010 Lennart Poettering
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  26
  27 <refentry id="systemd.path">
  28   <refentryinfo>
  29     <title>systemd.path</title>
  30     <productname>systemd</productname>
  31
  32     <authorgroup>
  33       <author>
  34         <contrib>Developer</contrib>
  35         <firstname>Lennart</firstname>
  36         <surname>Poettering</surname>
  37         <email>lennart@poettering.net</email>
  38       </author>
  39     </authorgroup>
  40   </refentryinfo>
  41
  42   <refmeta>
  43     <refentrytitle>systemd.path</refentrytitle>
  44     <manvolnum>5</manvolnum>
  45   </refmeta>
  46
  47   <refnamediv>
  48     <refname>systemd.path</refname>
  49     <refpurpose>Path unit configuration</refpurpose>
  50   </refnamediv>
  51
  52   <refsynopsisdiv>
  53     <para><filename><replaceable>path</replaceable>.path</filename></para>
  54   </refsynopsisdiv>
  55
  56   <refsect1>
  57     <title>Description</title>
  58
  59     <para>A unit configuration file whose name ends in
  60     <literal>.path</literal> encodes information about a path
  61     monitored by systemd, for path-based activation.</para>
  62
  63     <para>This man page lists the configuration options specific to
  64     this unit type. See
  65     <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
  66     for the common options of all unit configuration files. The common
  67     configuration items are configured in the generic [Unit] and
  68     [Install] sections. The path specific configuration options are
  69     configured in the [Path] section.</para>
  70
  71     <para>For each path file, a matching unit file must exist,
  72     describing the unit to activate when the path changes. By default,
  73     a service by the same name as the path (except for the suffix) is
  74     activated. Example: a path file <filename>foo.path</filename>
  75     activates a matching service <filename>foo.service</filename>. The
  76     unit to activate may be controlled by <varname>Unit=</varname>
  77     (see below).</para>
  78
  79     <para>Internally, path units use the
  80     <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  81     API to monitor file systems. Due to that, it suffers by the same
  82     limitations as inotify, and for example cannot be used to monitor
  83     files or directories changed by other machines on remote NFS file
  84     systems.</para>
  85
  86     <para>If a path unit is beneath another mount point in the file
  87     system hierarchy, a dependency between both units is created
  88     automatically.</para>
  89
  90     <para>Unless <varname>DefaultDependencies=false</varname> is used,
  91     path units will implicitly have dependencies of type
  92     <varname>Conflicts=</varname> and <varname>Before=</varname> on
  93     <filename>shutdown.target</filename>. These ensure that path units
  94     are terminated cleanly prior to system shutdown. Only path units
  95     involved with early boot or late system shutdown should disable
  96     this option.
  97     </para>
  98   </refsect1>
  99
 100   <refsect1>
 101     <title>Options</title>
 102
 103     <para>Path files must include a [Path] section, which carries
 104     information about the path(s) it monitors. The options specific to
 105     the [Path] section of path units are the following:</para>
 106
 107     <variablelist class='unit-directives'>
 108       <varlistentry>
 109         <term><varname>PathExists=</varname></term>
 110         <term><varname>PathExistsGlob=</varname></term>
 111         <term><varname>PathChanged=</varname></term>
 112         <term><varname>PathModified=</varname></term>
 113         <term><varname>DirectoryNotEmpty=</varname></term>
 114
 115         <listitem><para>Defines paths to monitor for certain changes:
 116         <varname>PathExists=</varname> may be used to watch the mere
 117         existence of a file or directory. If the file specified
 118         exists, the configured unit is activated.
 119         <varname>PathExistsGlob=</varname> works similar, but checks
 120         for the existence of at least one file matching the globbing
 121         pattern specified. <varname>PathChanged=</varname> may be used
 122         to watch a file or directory and activate the configured unit
 123         whenever it changes. It is not activated on every write to the
 124         watched file but it is activated if the file which was open
 125         for writing gets closed. <varname>PathModified=</varname> is
 126         similar, but additionally it is activated also on simple
 127         writes to the watched file.
 128         <varname>DirectoryNotEmpty=</varname> may be used to watch a
 129         directory and activate the configured unit whenever it
 130         contains at least one file.</para>
 131
 132         <para>The arguments of these directives must be absolute file
 133         system paths.</para>
 134
 135         <para>Multiple directives may be combined, of the same and of
 136         different types, to watch multiple paths. If the empty string
 137         is assigned to any of these options, the list of paths to
 138         watch is reset, and any prior assignments of these options
 139         will not have any effect.</para>
 140
 141         <para>If a path already exists (in case of
 142         <varname>PathExists=</varname> and
 143         <varname>PathExistsGlob=</varname>) or a directory already is
 144         not empty (in case of <varname>DirectoryNotEmpty=</varname>)
 145         at the time the path unit is activated, then the configured
 146         unit is immediately activated as well. Something similar does
 147         not apply to <varname>PathChanged=</varname> and
 148         <varname>PathModified=</varname>.</para>
 149
 150         <para>If the path itself or any of the containing directories
 151         are not accessible, <command>systemd</command> will watch for
 152         permission changes and notice that conditions are satisfied
 153         when permissions allow that. </para></listitem>
 154       </varlistentry>
 155       <varlistentry>
 156         <term><varname>Unit=</varname></term>
 157
 158         <listitem><para>The unit to activate when any of the
 159         configured paths changes. The argument is a unit name, whose
 160         suffix is not <literal>.path</literal>. If not specified, this
 161         value defaults to a service that has the same name as the path
 162         unit, except for the suffix. (See above.) It is recommended
 163         that the unit name that is activated and the unit name of the
 164         path unit are named identical, except for the
 165         suffix.</para></listitem>
 166       </varlistentry>
 167       <varlistentry>
 168         <term><varname>MakeDirectory=</varname></term>
 169
 170         <listitem><para>Takes a boolean argument. If true, the
 171         directories to watch are created before watching. This option
 172         is ignored for <varname>PathExists=</varname> settings.
 173         Defaults to <option>false</option>.</para></listitem>
 174       </varlistentry>
 175       <varlistentry>
 176         <term><varname>DirectoryMode=</varname></term>
 177
 178         <listitem><para>If <varname>MakeDirectory=</varname> is
 179         enabled, use the mode specified here to create the directories
 180         in question. Takes an access mode in octal notation. Defaults
 181         to <option>0755</option>.</para></listitem>
 182       </varlistentry>
 183     </variablelist>
 184   </refsect1>
 185
 186   <refsect1>
 187       <title>See Also</title>
 188       <para>
 189         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 190         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 191         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 192         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 193         <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 194         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 195       </para>
 196   </refsect1>
 197
 198 </refentry>