man/standard-conf.xml

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   2 <!DOCTYPE refsection PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3           "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
   4
   5 <refsection>
   6   <refsection id='confd'>
   7     <title>Configuration Directories and Precedence</title>
   8
   9     <para>Configuration files are read from directories in
  10     <filename>/etc/</filename>, <filename>/run/</filename>, and
  11     <filename>/usr/lib/</filename>, in order of precedence.
  12     Each configuration file in these configuration directories shall be named in
  13     the style of <filename><replaceable>filename</replaceable>.conf</filename>.
  14     Files in <filename>/etc/</filename> override files with the same name in
  15     <filename>/run/</filename> and <filename>/usr/lib/</filename>. Files in
  16     <filename>/run/</filename> override files with the same name in
  17     <filename>/usr/lib/</filename>.</para>
  18
  19     <para>Packages should install their configuration files in
  20     <filename>/usr/lib/</filename>. Files in <filename>/etc/</filename> are
  21     reserved for the local administrator, who may use this logic to override the
  22     configuration files installed by vendor packages. All configuration files
  23     are sorted by their filename in lexicographic order, regardless of which of
  24     the directories they reside in. If multiple files specify the same option,
  25     the entry in the file with the lexicographically latest name will take
  26     precedence. It is recommended to prefix all filenames with a two-digit number
  27     and a dash, to simplify the ordering of the files.</para>
  28
  29     <para>If the administrator wants to disable a configuration file supplied by
  30     the vendor, the recommended way is to place a symlink to
  31     <filename>/dev/null</filename> in the configuration directory in
  32     <filename>/etc/</filename>, with the same filename as the vendor
  33     configuration file.</para>
  34   </refsection>
  35
  36   <refsection id='main-conf'>
  37     <title>Configuration Directories and Precedence</title>
  38
  39     <para>Default configuration is defined during compilation, so a
  40     configuration file is only needed when it is necessary to deviate
  41     from those defaults. By default the configuration file in
  42     <filename>/etc/systemd/</filename> contains commented out entries
  43     showing the defaults as a guide to the administrator. This file
  44     can be edited to create local overrides.
  45     </para>
  46
  47     <para>When packages need to customize the configuration, they can
  48     install configuration snippets in
  49     <filename>/usr/lib/systemd/*.conf.d/</filename>. Files in
  50     <filename>/etc/</filename> are reserved for the local
  51     administrator, who may use this logic to override the
  52     configuration files installed by vendor packages. The main
  53     configuration file is read before any of the configuration
  54     directories, and has the lowest precedence; entries in a file in
  55     any configuration directory override entries in the single
  56     configuration file. Files in the
  57     <filename>*.conf.d/</filename> configuration subdirectories
  58     are sorted by their filename in lexicographic order, regardless of
  59     which of the subdirectories they reside in. If multiple files
  60     specify the same option, the entry in the file with the
  61     lexicographically latest name takes precedence.  It is recommended
  62     to prefix all filenames in those subdirectories with a two-digit
  63     number and a dash, to simplify the ordering of the files.</para>
  64
  65     <para>To disable a configuration file supplied by the vendor, the
  66     recommended way is to place a symlink to
  67     <filename>/dev/null</filename> in the configuration directory in
  68     <filename>/etc/</filename>, with the same filename as the vendor
  69     configuration file.</para>
  70   </refsection>
  71 </refsection>