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