man/standard-conf.xml

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   8   This file is part of systemd.
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  10   Copyright 2015 Zbigniew Jędrzejewski-Szmek
  11   Copyright 2014 Josh Triplett
  12
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  21   Lesser General Public License for more details.
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  26
  27 <refsection>
  28   <refsection id='confd'>
  29     <title>Configuration Directories and Precedence</title>
  30
  31     <para>Configuration files are read from directories in
  32     <filename>/etc/</filename>, <filename>/run/</filename>, and
  33     <filename>/usr/lib/</filename>, in order of precedence.
  34     Each configuration file in these configuration directories shall be named in
  35     the style of <filename><replaceable>filename</replaceable>.conf</filename>.
  36     Files in <filename>/etc/</filename> override files with the same name in
  37     <filename>/run/</filename> and <filename>/usr/lib/</filename>. Files in
  38     <filename>/run/</filename> override files with the same name in
  39     <filename>/usr/lib/</filename>.</para>
  40
  41     <para>Packages should install their configuration files in
  42     <filename>/usr/lib/</filename>. Files in <filename>/etc/</filename> are
  43     reserved for the local administrator, who may use this logic to override the
  44     configuration files installed by vendor packages. All configuration files
  45     are sorted by their filename in lexicographic order, regardless of which of
  46     the directories they reside in. If multiple files specify the same option,
  47     the entry in the file with the lexicographically latest name will take
  48     precedence. It is recommended to prefix all filenames with a two-digit number
  49     and a dash, to simplify the ordering of the files.</para>
  50
  51     <para>If the administrator wants to disable a configuration file supplied by
  52     the vendor, the recommended way is to place a symlink to
  53     <filename>/dev/null</filename> in the configuration directory in
  54     <filename>/etc/</filename>, with the same filename as the vendor
  55     configuration file. If the vendor configuration file is included in
  56     the initrd image, the image has to be regenerated.</para>
  57   </refsection>
  58
  59   <refsection id='main-conf'>
  60     <title>Configuration Directories and Precedence</title>
  61
  62     <para>The default configuration is defined during compilation, so a
  63     configuration file is only needed when it is necessary to deviate
  64     from those defaults. By default, the configuration file in
  65     <filename>/etc/systemd/</filename> contains commented out entries
  66     showing the defaults as a guide to the administrator. This file
  67     can be edited to create local overrides.
  68     </para>
  69
  70     <para>When packages need to customize the configuration, they can
  71     install configuration snippets in
  72     <filename>/usr/lib/systemd/*.conf.d/</filename>. Files in
  73     <filename>/etc/</filename> are reserved for the local
  74     administrator, who may use this logic to override the
  75     configuration files installed by vendor packages. The main
  76     configuration file is read before any of the configuration
  77     directories, and has the lowest precedence; entries in a file in
  78     any configuration directory override entries in the single
  79     configuration file. Files in the <filename>*.conf.d/</filename>
  80     configuration subdirectories are sorted by their filename in lexicographic
  81     order, regardless of which of the subdirectories they reside in. When
  82     multiple files specify the same option, for options which accept just a
  83     single value, the entry in the file with the lexicographically latest name
  84     takes precedence. For options which accept a list of values, entries are
  85     collected as they occur in files sorted lexicographically. It is recommended
  86     to prefix all filenames in those subdirectories with a two-digit number and
  87     a dash, to simplify the ordering of the files.</para>
  88
  89     <para>To disable a configuration file supplied by the vendor, the
  90     recommended way is to place a symlink to
  91     <filename>/dev/null</filename> in the configuration directory in
  92     <filename>/etc/</filename>, with the same filename as the vendor
  93     configuration file.</para>
  94   </refsection>
  95 </refsection>