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| <!-- |
| SPDX-License-Identifier: LGPL-2.1-or-later |
| Copyright © 2014 Josh Triplett |
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| |
| <refsection> |
| <refsection id='confd'> |
| <title>Configuration Directories and Precedence</title> |
| |
| <para>Configuration files are read from directories in <filename>/etc/</filename>, |
| <filename>/run/</filename>, <filename>/usr/local/lib/</filename>, and <filename>/usr/lib/</filename>, in |
| order of precedence, as listed in the SYNOPSIS section above. Files must have the |
| <literal>.conf</literal> extension. Files in <filename>/etc/</filename> override files with the same name |
| in <filename>/run/</filename>, <filename>/usr/local/lib/</filename>, and |
| <filename>/usr/lib/</filename>. Files in <filename>/run/</filename> override files with the same name |
| under <filename>/usr/</filename>.</para> |
| |
| <para>All configuration files are sorted by their filename in lexicographic order, regardless of which of |
| the directories they reside in. If multiple files specify the same option, the entry in the file with the |
| lexicographically latest name will take precedence. Thus, the configuration in a certain file may either |
| be replaced completely (by placing a file with the same name in a directory with higher priority), or |
| individual settings might be changed (by specifying additional settings in a file with a different name |
| that is ordered later).</para> |
| |
| <para>Packages should install their configuration files in <filename>/usr/lib/</filename> (distribution |
| packages) or <filename>/usr/local/lib/</filename> (local installs). Files in <filename>/etc/</filename> |
| are reserved for the local administrator, who may use this logic to override the configuration files |
| installed by vendor packages. It is recommended to prefix all filenames with a two-digit number and a |
| dash, to simplify the ordering of the files.</para> |
| |
| <para>If the administrator wants to disable a configuration file supplied by the vendor, the recommended |
| way is to place a symlink to <filename>/dev/null</filename> in the configuration directory in |
| <filename>/etc/</filename>, with the same filename as the vendor configuration file. If the vendor |
| configuration file is included in the initrd image, the image has to be regenerated.</para> |
| </refsection> |
| |
| <refsection id='main-conf'> |
| <title>Configuration Directories and Precedence</title> |
| |
| <para>The default configuration is set during compilation, so configuration is only needed when it is |
| necessary to deviate from those defaults. Initially, the main configuration file in |
| <filename>/etc/systemd/</filename> contains commented out entries showing the defaults as a guide to the |
| administrator. Local overrides can be created by editing this file or by creating drop-ins, as described |
| below. Using drop-ins for local configuration is recommended over modifications to the main configuration |
| file.</para> |
| |
| <para>In addition to the "main" configuration file, drop-in configuration snippets are read from |
| <filename>/usr/lib/systemd/*.conf.d/</filename>, <filename>/usr/local/lib/systemd/*.conf.d/</filename>, |
| and <filename>/etc/systemd/*.conf.d/</filename>. Those drop-ins have higher precedence and override the |
| main configuration file. Files in the <filename>*.conf.d/</filename> configuration subdirectories are |
| sorted by their filename in lexicographic order, regardless of in which of the subdirectories they |
| reside. When multiple files specify the same option, for options which accept just a single value, the |
| entry in the file sorted last takes precedence, and for options which accept a list of values, entries |
| are collected as they occur in the sorted files.</para> |
| |
| <para>When packages need to customize the configuration, they can install drop-ins under |
| <filename>/usr/</filename>. Files in <filename>/etc/</filename> are reserved for the local administrator, |
| who may use this logic to override the configuration files installed by vendor packages. Drop-ins have to |
| be used to override package drop-ins, since the main configuration file has lower precedence. It is |
| recommended to prefix all filenames in those subdirectories with a two-digit number and a dash, to |
| simplify the ordering of the files.</para> |
| |
| <para>To disable a configuration file supplied by the vendor, the recommended way is to place a symlink |
| to <filename>/dev/null</filename> in the configuration directory in <filename>/etc/</filename>, with the |
| same filename as the vendor configuration file.</para> |
| </refsection> |
| </refsection> |