man/standard-conf.xml

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   7   Copyright © 2014 Josh Triplett
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   9
  10 <refsection>
  11   <refsection id='confd'>
  12     <title>Configuration Directories and Precedence</title>
  13
  14     <para>Configuration files are read from directories in <filename>/etc/</filename>,
  15     <filename>/run/</filename>, <filename>/usr/local/lib/</filename>, and <filename>/usr/lib/</filename>, in
  16     order of precedence, as listed in the SYNOPSIS section above. Files must have the
  17     <literal>.conf</literal> extension. Files in <filename>/etc/</filename> override files with the same name
  18     in <filename>/run/</filename>, <filename>/usr/local/lib/</filename>, and
  19     <filename>/usr/lib/</filename>. Files in <filename>/run/</filename> override files with the same name
  20     under <filename>/usr/</filename>.</para>
  21
  22     <para>All configuration files are sorted by their filename in lexicographic order, regardless of which of
  23     the directories they reside in. If multiple files specify the same option, the entry in the file with the
  24     lexicographically latest name will take precedence. Thus, the configuration in a certain file may either
  25     be replaced completely (by placing a file with the same name in a directory with higher priority), or
  26     individual settings might be changed (by specifying additional settings in a file with a different name
  27     that is ordered later).</para>
  28
  29     <para>Packages should install their configuration files in <filename>/usr/lib/</filename> (distribution
  30     packages) or <filename>/usr/local/lib/</filename> (local installs). Files in <filename>/etc/</filename>
  31     are reserved for the local administrator, who may use this logic to override the configuration files
  32     installed by vendor packages. It is recommended to prefix all filenames with a two-digit number and a
  33     dash, to simplify the ordering of the files.</para>
  34
  35     <para>If the administrator wants to disable a configuration file supplied by the vendor, the recommended
  36     way is to place a symlink to <filename>/dev/null</filename> in the configuration directory in
  37     <filename>/etc/</filename>, with the same filename as the vendor configuration file. If the vendor
  38     configuration file is included in the initrd image, the image has to be regenerated.</para>
  39   </refsection>
  40
  41   <refsection id='main-conf'>
  42     <title>Configuration Directories and Precedence</title>
  43
  44     <para>The default configuration is defined during compilation, so a
  45     configuration file is only needed when it is necessary to deviate
  46     from those defaults. By default, the configuration file in
  47     <filename>/etc/systemd/</filename> contains commented out entries
  48     showing the defaults as a guide to the administrator. This file
  49     can be edited to create local overrides.
  50     </para>
  51
  52     <para>When packages need to customize the configuration, they can install configuration snippets in
  53     <filename>/usr/lib/systemd/*.conf.d/</filename> or <filename>/usr/local/lib/systemd/*.conf.d/</filename>.
  54     The main configuration file is read before any of the configuration directories, and has the lowest
  55     precedence; entries in a file in any configuration directory override entries in the single configuration
  56     file. Files in the <filename>*.conf.d/</filename> configuration subdirectories are sorted by their
  57     filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple
  58     files specify the same option, for options which accept just a single value, the entry in the file with
  59     the lexicographically latest name takes precedence. For options which accept a list of values, entries
  60     are collected as they occur in files sorted lexicographically.</para>
  61
  62     <para>Files in <filename>/etc/</filename> are reserved for the local administrator, who may use this
  63     logic to override the configuration files installed by vendor packages. It is recommended to prefix all
  64     filenames in those subdirectories with a two-digit number and a dash, to simplify the ordering of the
  65     files.</para>
  66
  67     <para>To disable a configuration file supplied by the vendor, the
  68     recommended way is to place a symlink to
  69     <filename>/dev/null</filename> in the configuration directory in
  70     <filename>/etc/</filename>, with the same filename as the vendor
  71     configuration file.</para>
  72   </refsection>
  73 </refsection>