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>Automatic Dependencies</title>
  86
  87     <para>If a path unit is beneath another mount unit in the file
  88     system hierarchy, both a requirement and an ordering dependency
  89     between both units are created automatically.</para>
  90
  91     <para>An implicit <varname>Before=</varname> dependency is added
  92     between a path unit and the unit it is supposed to activate.</para>
  93
  94     <para>Unless <varname>DefaultDependencies=false</varname> is used,
  95     path units will implicitly have dependencies of type
  96     <varname>Before=</varname> on <filename>paths.target</filename>,
  97     dependencies of type <varname>After=</varname> and
  98     <varname>Requires=</varname> on
  99     <filename>sysinit.target</filename>, and have dependencies of type
 100     <varname>Conflicts=</varname> and <varname>Before=</varname> on
 101     <filename>shutdown.target</filename>. These ensure that path units
 102     are terminated cleanly prior to system shutdown. Only path units
 103     involved with early boot or late system shutdown should disable
 104     this option.
 105     </para>
 106   </refsect1>
 107
 108   <refsect1>
 109     <title>Options</title>
 110
 111     <para>Path files must include a [Path] section, which carries
 112     information about the path(s) it monitors. The options specific to
 113     the [Path] section of path units are the following:</para>
 114
 115     <variablelist class='unit-directives'>
 116       <varlistentry>
 117         <term><varname>PathExists=</varname></term>
 118         <term><varname>PathExistsGlob=</varname></term>
 119         <term><varname>PathChanged=</varname></term>
 120         <term><varname>PathModified=</varname></term>
 121         <term><varname>DirectoryNotEmpty=</varname></term>
 122
 123         <listitem><para>Defines paths to monitor for certain changes:
 124         <varname>PathExists=</varname> may be used to watch the mere
 125         existence of a file or directory. If the file specified
 126         exists, the configured unit is activated.
 127         <varname>PathExistsGlob=</varname> works similar, but checks
 128         for the existence of at least one file matching the globbing
 129         pattern specified. <varname>PathChanged=</varname> may be used
 130         to watch a file or directory and activate the configured unit
 131         whenever it changes. It is not activated on every write to the
 132         watched file but it is activated if the file which was open
 133         for writing gets closed. <varname>PathModified=</varname> is
 134         similar, but additionally it is activated also on simple
 135         writes to the watched file.
 136         <varname>DirectoryNotEmpty=</varname> may be used to watch a
 137         directory and activate the configured unit whenever it
 138         contains at least one file.</para>
 139
 140         <para>The arguments of these directives must be absolute file
 141         system paths.</para>
 142
 143         <para>Multiple directives may be combined, of the same and of
 144         different types, to watch multiple paths. If the empty string
 145         is assigned to any of these options, the list of paths to
 146         watch is reset, and any prior assignments of these options
 147         will not have any effect.</para>
 148
 149         <para>If a path already exists (in case of
 150         <varname>PathExists=</varname> and
 151         <varname>PathExistsGlob=</varname>) or a directory already is
 152         not empty (in case of <varname>DirectoryNotEmpty=</varname>)
 153         at the time the path unit is activated, then the configured
 154         unit is immediately activated as well. Something similar does
 155         not apply to <varname>PathChanged=</varname> and
 156         <varname>PathModified=</varname>.</para>
 157
 158         <para>If the path itself or any of the containing directories
 159         are not accessible, <command>systemd</command> will watch for
 160         permission changes and notice that conditions are satisfied
 161         when permissions allow that. </para></listitem>
 162       </varlistentry>
 163       <varlistentry>
 164         <term><varname>Unit=</varname></term>
 165
 166         <listitem><para>The unit to activate when any of the
 167         configured paths changes. The argument is a unit name, whose
 168         suffix is not <literal>.path</literal>. If not specified, this
 169         value defaults to a service that has the same name as the path
 170         unit, except for the suffix. (See above.) It is recommended
 171         that the unit name that is activated and the unit name of the
 172         path unit are named identical, except for the
 173         suffix.</para></listitem>
 174       </varlistentry>
 175       <varlistentry>
 176         <term><varname>MakeDirectory=</varname></term>
 177
 178         <listitem><para>Takes a boolean argument. If true, the
 179         directories to watch are created before watching. This option
 180         is ignored for <varname>PathExists=</varname> settings.
 181         Defaults to <option>false</option>.</para></listitem>
 182       </varlistentry>
 183       <varlistentry>
 184         <term><varname>DirectoryMode=</varname></term>
 185
 186         <listitem><para>If <varname>MakeDirectory=</varname> is
 187         enabled, use the mode specified here to create the directories
 188         in question. Takes an access mode in octal notation. Defaults
 189         to <option>0755</option>.</para></listitem>
 190       </varlistentry>
 191     </variablelist>
 192   </refsect1>
 193
 194   <refsect1>
 195       <title>See Also</title>
 196       <para>
 197         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 198         <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 199         <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 200         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 201         <citerefentry project='man-pages'><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 202         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 203       </para>
 204   </refsect1>
 205
 206 </refentry>