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. If the vendor configuration file is included in
  34     the initrd image, the image has to be regenerated.</para>
  35   </refsection>
  36
  37   <refsection id='main-conf'>
  38     <title>Configuration Directories and Precedence</title>
  39
  40     <para>The default configuration is defined during compilation, so a
  41     configuration file is only needed when it is necessary to deviate
  42     from those defaults. By default, the configuration file in
  43     <filename>/etc/systemd/</filename> contains commented out entries
  44     showing the defaults as a guide to the administrator. This file
  45     can be edited to create local overrides.
  46     </para>
  47
  48     <para>When packages need to customize the configuration, they can
  49     install configuration snippets in
  50     <filename>/usr/lib/systemd/*.conf.d/</filename>. Files in
  51     <filename>/etc/</filename> are reserved for the local
  52     administrator, who may use this logic to override the
  53     configuration files installed by vendor packages. The main
  54     configuration file is read before any of the configuration
  55     directories, and has the lowest precedence; entries in a file in
  56     any configuration directory override entries in the single
  57     configuration file. Files in the <filename>*.conf.d/</filename>
  58     configuration subdirectories are sorted by their filename in lexicographic
  59     order, regardless of which of the subdirectories they reside in. When
  60     multiple files specify the same option, for options which accept just a
  61     single value, the entry in the file with the lexicographically latest name
  62     takes precedence. For options which accept a list of values, entries are
  63     collected as they occur in files sorted lexicographically. It is recommended
  64     to prefix all filenames in those subdirectories with a two-digit number and
  65     a dash, to simplify the ordering of the 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>