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man: rework section about configuration file precedence 

This section is loaded in a bunch of places, so this affects many
man pages.

1. point the reader to the synopsis section, which has the exact paths
that are used to load files.
2. put the "reference" part first, and recommendations later, in separate
paragraphs.
3. describe how individual settings and whole files are replaces.

Closes #12791.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2020-01-16 14:10:18 +01:00
parent 251d3d20c3
commit e76c60bf2a
1 changed files with 37 additions and 41 deletions
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78
man/standard-conf.xml
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@ -11,30 +11,31 @@
<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. Each
configuration file in these configuration directories shall be named in the style of
<filename><replaceable>filename</replaceable>.conf</filename>. 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>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 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>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. 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. It is recommended to prefix all filenames with a two-digit number
and a dash, to simplify the ordering of the files.</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>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>
<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'>
@ -48,25 +49,20 @@
can be edited to create local overrides.
</para>
<para>When packages need to customize the configuration, they can
install configuration snippets in
<filename>/usr/lib/systemd/*.conf.d/</filename> or
<filename>/usr/local/lib/systemd/*.conf.d/</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. The main
configuration file is read before any of the configuration
directories, and has the lowest precedence; entries in a file in
any configuration directory override entries in the single
configuration file. Files in the <filename>*.conf.d/</filename>
configuration subdirectories are sorted by their filename in lexicographic
order, regardless of which of the subdirectories they reside in. When
multiple files specify the same option, for options which accept just a
single value, the entry in the file with the lexicographically latest name
takes precedence. For options which accept a list of values, entries are
collected as they occur in files sorted lexicographically. 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>When packages need to customize the configuration, they can install configuration snippets in
<filename>/usr/lib/systemd/*.conf.d/</filename> or <filename>/usr/local/lib/systemd/*.conf.d/</filename>.
The main configuration file is read before any of the configuration directories, and has the lowest
precedence; entries in a file in any configuration directory override entries in the single 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 with
the lexicographically latest name takes precedence. For options which accept a list of values, entries
are collected as they occur in files sorted lexicographically.</para>
<para>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 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