- identify and compare configuration files in
- <filename>/etc</filename> that override default
- counterparts in <filename>/usr</filename>. The command
- line argument can be one or more name of a subdirectories of
- <filename>/etc</filename> or
- <filename>/usr/lib</filename> to compare, such as
- <filename>tmpfiles.d</filename>, <filename>sysctl.d</filename> or
- <filename>systemd/system</filename>.</para>
-
- <para>When no argument is specified a number of
- well-known subdirectories are searched for overridden
- files.</para>
+ identify and compare configuration files that override
+ other configuration files. Files in
+ <filename>/etc</filename> have highest priority, files
+ in <filename>/run</filename> have the second highest
+ priority, ..., files in <filename>/lib</filename> have
+ lowest priority. Files in a directory with higher
+ priority override files with the same name in
+ directories of lower priority. In addition, certain
+ configuration files can have <literal>.d</literal>
+ directories which contain "drop-in" files with
+ configuration snippets which augment the main
+ configuration file. "Drop-in" files can be overriden
+ in the same way by placing files with the same name in
+ a directory of higher priority (except that in case of
+ "drop-in" files, both the "drop-in" file name and the
+ name of the containing directory, which corresponds to
+ the name of the main configuration file, must match).
+ For a fuller explanation, see
+ <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
+ </para>
+
+ <para>The command line argument will be split into a
+ prefix and a suffix. Either is optional. The prefix
+ must be one of the directories containing
+ configuration files (<filename>/etc</filename>,
+ <filename>/run</filename>,
+ <filename>/usr/lib</filename>, ...). If it is given,
+ only overriding files contained in this directory will
+ be shown. Otherwise, all overriding files will be
+ shown. The suffix must be a name of a subdirectory
+ containing configuration files like
+ <filename>tmpfiles.d</filename>,
+ <filename>sysctl.d</filename> or
+ <filename>systemd/system</filename>. If it is given,
+ only configuration files in this subdirectory (across
+ all configuration paths) will be analyzed. Otherwise,
+ all configuration files will be analyzed. If the
+ commandline argument is not given at all, all
+ configuration files will be analyzed. See below for
+ some examples.</para>