Do not advertise .d snippets over main config file

For daemons which have a main configuration file, there's
little reason for the administrator to use configuration snippets.
They are useful for packagers which need to override settings, but
we shouldn't advertise that as the main way of configuring those
services.

https://bugs.freedesktop.org/show_bug.cgi?id=89397

man/bootchart.conf.xml

@@ -68,8 +68,7 @@
     parameters and graph output.</para>
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
 
   <refsect1>
     <title>Options</title>

man/coredump.conf.xml

@@ -63,8 +63,7 @@
     a handler for core dumps invoked by the kernel.</para>
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
 
   <refsect1>
     <title>Options</title>

man/journald.conf.xml

@@ -64,8 +64,7 @@
 
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
 
   <refsect1>
     <title>Options</title>

man/logind.conf.xml

@@ -58,11 +58,13 @@
   <refsect1>
     <title>Description</title>
 
-    <para>These files configure various parameters of the systemd login manager, <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
+    <para>These files configure various parameters of the systemd
+    login manager,
+    <citerefentry><refentrytitle>systemd-logind.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
+    </para>
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
 
   <refsect1>
     <title>Options</title>

man/resolved.conf.xml

@@ -63,8 +63,7 @@
 
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
 
   <refsect1>
     <title>Options</title>

man/standard-conf.xml

@@ -33,13 +33,39 @@
     configuration file.</para>
   </refsection>
 
-  <refsection id='conf'>
+  <refsection id='main-conf'>
-    <title>Configuration File</title>
+    <title>Configuration Directories and Precedence</title>
 
-    <para>Configuration is also read from a single configuration file in
+    <para>Default configuration is defined during compilation, so a
-    <filename>/etc/</filename>. This file is read before any of the
+    configuration file is only needed when it is necessary to deviate
-    configuration directories, and has the lowest precedence; entries in a file
+    from those defaults. By default the configuration file in
-    in any configuration directory override entries in the single configuration
+    <filename>/etc/systemd/</filename> contains commented out entries
-    file.</para>
+    showing the defaults as a guide to the administrator. This file
+    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>. 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>logind.conf.d/</filename> configuration subdirectories
+    are sorted by their filename in lexicographic order, regardless of
+    which of the subdirectories they reside in. If multiple files
+    specify the same option, the entry in the file with the
+    lexicographically latest name takes 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>

man/systemd-sleep.conf.xml

@@ -112,8 +112,7 @@ along with systemd; If not, see <http://www.gnu.org/licenses/>.
     attempts to suspend or hibernate the machine.</para>
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
 
   <refsect1>
     <title>Options</title>

man/systemd-system.conf.xml

@@ -74,8 +74,7 @@
     operations.</para>
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
 
   <refsect1>
     <title>Options</title>

man/timesyncd.conf.xml

@@ -63,8 +63,7 @@
 
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
 
   <refsect1>
     <title>Options</title>

src/bootchart/bootchart.conf

@@ -5,10 +5,11 @@
 #  the Free Software Foundation; either version 2.1 of the License, or
 #  (at your option) any later version.
 #
-# You can override the directives in this file by creating files in
+# Entries in this file show the compile time defaults.
-# /etc/systemd/bootchart.conf.d/*.conf.
+# You can change settings by editing this file.
+# Defaults can be restored by simply deleting this file.
 #
-# See bootchart.conf(5) for details
+# See bootchart.conf(5) for details.
 
 [Bootchart]
 #Samples=500

src/core/system.conf

@@ -5,10 +5,11 @@
 #  the Free Software Foundation; either version 2.1 of the License, or
 #  (at your option) any later version.
 #
-# You can override the directives in this file by creating files in
+# Entries in this file show the compile time defaults.
-# /etc/systemd/system.conf.d/*.conf.
+# You can change settings by editing this file.
+# Defaults can be restored by simply deleting this file.
 #
-# See systemd-system.conf(5) for details
+# See systemd-system.conf(5) for details.
 
 [Manager]
 #LogLevel=info

src/journal/coredump.conf

@@ -5,10 +5,11 @@
 #  the Free Software Foundation; either version 2.1 of the License, or
 #  (at your option) any later version.
 #
-# You can override the directives in this file by creating files in
+# Entries in this file show the compile time defaults.
-# /etc/systemd/coredump.conf.d/*.conf.
+# You can change settings by editing this file.
+# Defaults can be restored by simply deleting this file.
 #
-# See coredump.conf(5) for details
+# See coredump.conf(5) for details.
 
 [Coredump]
 #Storage=external

src/journal/journald.conf

@@ -5,10 +5,11 @@
 #  the Free Software Foundation; either version 2.1 of the License, or
 #  (at your option) any later version.
 #
-# You can override the directives in this file by creating files in
+# Entries in this file show the compile time defaults.
-# /etc/systemd/journald.conf.d/*.conf.
+# You can change settings by editing this file.
+# Defaults can be restored by simply deleting this file.
 #
-# See journald.conf(5) for details
+# See journald.conf(5) for details.
 
 [Journal]
 #Storage=auto

src/login/logind.conf

@@ -5,10 +5,11 @@
 #  the Free Software Foundation; either version 2.1 of the License, or
 #  (at your option) any later version.
 #
-# You can override the directives in this file by creating files in
+# Entries in this file show the compile time defaults.
-# /etc/systemd/logind.conf.d/*.conf.
+# You can change settings by editing this file.
+# Defaults can be restored by simply deleting this file.
 #
-# See logind.conf(5) for details
+# See logind.conf(5) for details.
 
 [Login]
 #NAutoVTs=6

src/resolve/resolved.conf.in

@@ -5,8 +5,9 @@
 #  the Free Software Foundation; either version 2.1 of the License, or
 #  (at your option) any later version.
 #
-# You can override the directives in this file by creating files in
+# Entries in this file show the compile time defaults.
-# /etc/systemd/resolved.conf.d/*.conf.
+# You can change settings by editing this file.
+# Defaults can be restored by simply deleting this file.
 #
 # See resolved.conf(5) for details
 

src/timesync/timesyncd.conf.in

@@ -5,10 +5,11 @@
 #  the Free Software Foundation; either version 2.1 of the License, or
 #  (at your option) any later version.
 #
-# You can override the directives in this file by creating files in
+# Entries in this file show the compile time defaults.
-# /etc/systemd/timesyncd.conf.d/*.conf.
+# You can change settings by editing this file.
+# Defaults can be restored by simply deleting this file.
 #
-# See timesyncd.conf(5) for details
+# See timesyncd.conf(5) for details.
 
 [Time]
 #NTP=