man/systemd.path.xml

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   9   Copyright 2010 Lennart Poettering
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  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><replaceable>path</replaceable>.path</filename></para>
  52         </refsynopsisdiv>
  53
  54         <refsect1>
  55                 <title>Description</title>
  56
  57                 <para>A unit configuration file whose name ends in
  58                 <literal>.path</literal> 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=false</varname>
  92                 is used, path units will implicitly have dependencies of
  93                 type <varname>Conflicts=</varname> and
  94                 <varname>Before=</varname> on
  95                 <filename>shutdown.target</filename>. These ensure
  96                 that path units are terminated cleanly prior to system
  97                 shutdown. Only path units involved with early boot or
  98                 late system shutdown should disable this option.
  99                 </para>
 100         </refsect1>
 101
 102         <refsect1>
 103                 <title>Options</title>
 104
 105                 <para>Path files must include a [Path] section,
 106                 which carries information about the path(s) it
 107                 monitors. The options specific to the [Path] section
 108                 of path units are the following:</para>
 109
 110                 <variablelist class='unit-directives'>
 111                         <varlistentry>
 112                                 <term><varname>PathExists=</varname></term>
 113                                 <term><varname>PathExistsGlob=</varname></term>
 114                                 <term><varname>PathChanged=</varname></term>
 115                                 <term><varname>PathModified=</varname></term>
 116                                 <term><varname>DirectoryNotEmpty=</varname></term>
 117
 118                                 <listitem><para>Defines paths to
 119                                 monitor for certain changes:
 120                                 <varname>PathExists=</varname> may be
 121                                 used to watch the mere existence of a
 122                                 file or directory. If the file
 123                                 specified exists, the configured unit
 124                                 is
 125                                 activated. <varname>PathExistsGlob=</varname>
 126                                 works similar, but checks for the
 127                                 existence of at least one file
 128                                 matching the globbing pattern
 129                                 specified. <varname>PathChanged=</varname>
 130                                 may be used to watch a file or
 131                                 directory and activate the configured
 132                                 unit whenever it changes. It is not
 133                                 activated on every write to the
 134                                 watched file but it is activated if
 135                                 the file which was open for writing
 136                                 gets
 137                                 closed. <varname>PathModified=</varname>
 138                                 is similar, but additionally it is
 139                                 activated also on simple writes to the
 140                                 watched file.
 141                                 <varname>DirectoryNotEmpty=</varname>
 142                                 may be used to watch a directory and
 143                                 activate the configured unit whenever
 144                                 it contains at least one file.</para>
 145
 146                                 <para>The arguments of these
 147                                 directives must be absolute file
 148                                 system paths.</para>
 149
 150                                 <para>Multiple directives may be
 151                                 combined, of the same and of different
 152                                 types, to watch multiple paths. If the
 153                                 empty string is assigned to any of
 154                                 these options, the list of paths to
 155                                 watch is reset, and any prior
 156                                 assignments of these options will not
 157                                 have any effect.</para>
 158
 159                                 <para>If a path already exists
 160                                 (in case of
 161                                 <varname>PathExists=</varname> and
 162                                 <varname>PathExistsGlob=</varname>) or
 163                                 a directory already is not empty (in
 164                                 case of
 165                                 <varname>DirectoryNotEmpty=</varname>)
 166                                 at the time the path unit is
 167                                 activated, then the configured unit is
 168                                 immediately activated as
 169                                 well. Something similar does not apply
 170                                 to <varname>PathChanged=</varname> and
 171                                 <varname>PathModified=</varname>.</para>
 172
 173                                 <para>If the path itself or any of the
 174                                 containing directories are not
 175                                 accessible, <command>systemd</command>
 176                                 will watch for permission changes and
 177                                 notice that conditions are satisfied
 178                                 when permissions allow that.
 179                                 </para></listitem>
 180                         </varlistentry>
 181                         <varlistentry>
 182                                 <term><varname>Unit=</varname></term>
 183
 184                                 <listitem><para>The unit to activate
 185                                 when any of the configured paths
 186                                 changes. The argument is a unit name,
 187                                 whose suffix is not
 188                                 <literal>.path</literal>. If not
 189                                 specified, this value defaults to a
 190                                 service that has the same name as the
 191                                 path unit, except for the suffix. (See
 192                                 above.) It is recommended that the
 193                                 unit name that is activated and the
 194                                 unit name of the path unit are named
 195                                 identical, except for the
 196                                 suffix.</para></listitem>
 197                         </varlistentry>
 198                         <varlistentry>
 199                                 <term><varname>MakeDirectory=</varname></term>
 200
 201                                 <listitem><para>Takes a boolean
 202                                 argument. If true, the directories to
 203                                 watch are created before
 204                                 watching. This option is ignored for
 205                                 <varname>PathExists=</varname>
 206                                 settings. Defaults to
 207                                 <option>false</option>.</para></listitem>
 208                         </varlistentry>
 209                         <varlistentry>
 210                                 <term><varname>DirectoryMode=</varname></term>
 211
 212                                 <listitem><para>If
 213                                 <varname>MakeDirectory=</varname> is
 214                                 enabled, use the mode specified here to
 215                                 create the directories in
 216                                 question. Takes an access mode in
 217                                 octal notation. Defaults to
 218                                 <option>0755</option>.</para></listitem>
 219                         </varlistentry>
 220                 </variablelist>
 221         </refsect1>
 222
 223         <refsect1>
 224                   <title>See Also</title>
 225                   <para>
 226                           <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 227                           <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 228                           <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 229                           <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 230                           <citerefentry><refentrytitle>inotify</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
 231                           <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 232                   </para>
 233         </refsect1>
 234
 235 </refentry>