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>Path unit configuration</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 a 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>PathExistsGlob=</varname></term>
 115                                 <term><varname>PathChanged=</varname></term>
 116                                 <term><varname>PathModified=</varname></term>
 117                                 <term><varname>DirectoryNotEmpty=</varname></term>
 118
 119                                 <listitem><para>Defines paths to
 120                                 monitor for certain changes:
 121                                 <varname>PathExists=</varname> may be
 122                                 used to watch the mere existence of a
 123                                 file or directory. If the file
 124                                 specified exists the configured unit
 125                                 is
 126                                 activated. <varname>PathExistsGlob=</varname>
 127                                 works similar, but checks for the
 128                                 existence of at least one file
 129                                 matching the globbing pattern
 130                                 specified. <varname>PathChanged=</varname>
 131                                 may be used to watch a file or
 132                                 directory and activate the configured
 133                                 unit whenever it changes. It is not
 134                                 activated on every write to the
 135                                 watched file but it is activated if
 136                                 the file which was open for writing
 137                                 gets
 138                                 closed. <varname>PathModified=</varname>
 139                                 is similar, but additionally it is
 140                                 activated also on simple writes to the
 141                                 watched file.
 142                                 <varname>DirectoryNotEmpty=</varname>
 143                                 may be used to watch a directory and
 144                                 activate the configured unit whenever
 145                                 it contains at least one file.</para>
 146
 147                                 <para>The arguments of these
 148                                 directives must be absolute file
 149                                 system paths.</para>
 150
 151                                 <para>Multiple directives may be
 152                                 combined, of the same and of different
 153                                 types, to watch multiple paths. If the
 154                                 empty string is assigned to any of
 155                                 these options the list of paths to
 156                                 watch is reset, and any prior
 157                                 assignments of these options will not
 158                                 have any effect.</para>
 159
 160                                 <para>If a path is already existing
 161                                 (in case of
 162                                 <varname>PathExists=</varname> and
 163                                 <varname>PathExistsGlob=</varname>) or
 164                                 a directory already is not empty (in
 165                                 case of
 166                                 <varname>DirectoryNotEmpty=</varname>)
 167                                 at the time the path unit is
 168                                 activated, then the configured unit is
 169                                 immediately activated as
 170                                 well. Something similar does not apply
 171                                 to <varname>PathChanged=</varname>.
 172                                 </para></listitem>
 173                         </varlistentry>
 174                         <varlistentry>
 175                                 <term><varname>Unit=</varname></term>
 176
 177                                 <listitem><para>The unit to activate
 178                                 when any of the configured paths
 179                                 changes. The argument is a unit name,
 180                                 whose suffix is not
 181                                 <filename>.path</filename>. If not
 182                                 specified, this value defaults to a
 183                                 service that has the same name as the
 184                                 path unit, except for the suffix. (See
 185                                 above.) It is recommended that the
 186                                 unit name that is activated and the
 187                                 unit name of the path unit are named
 188                                 identical, except for the
 189                                 suffix.</para></listitem>
 190                         </varlistentry>
 191                         <varlistentry>
 192                                 <term><varname>MakeDirectory=</varname></term>
 193
 194                                 <listitem><para>Takes a boolean
 195                                 argument. If true the directories to
 196                                 watch are created before
 197                                 watching. This option is ignored for
 198                                 <varname>PathExists=</varname>
 199                                 settings. Defaults to
 200                                 <option>false</option>.</para></listitem>
 201                         </varlistentry>
 202                         <varlistentry>
 203                                 <term><varname>DirectoryMode=</varname></term>
 204
 205                                 <listitem><para>If
 206                                 <varname>MakeDirectory=</varname> is
 207                                 enabled use the mode specified here to
 208                                 create the directories in
 209                                 question. Takes an access mode in
 210                                 octal notation. Defaults to
 211                                 <option>0755</option>.</para></listitem>
 212                         </varlistentry>
 213                 </variablelist>
 214         </refsect1>
 215
 216         <refsect1>
 217                   <title>See Also</title>
 218                   <para>
 219                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 220                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 221                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 222                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 223                           <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 224                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 225                   </para>
 226         </refsect1>
 227
 228 </refentry>