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

16 files changed, 73 insertions, 45 deletions

diff --git a/man/bootchart.conf.xml b/man/bootchart.conf.xml
index 8d9700d300..bf6ca0bf9e 100644
--- a/man/bootchart.conf.xml
+++ b/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="conf" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
 
   <refsect1>
     <title>Options</title>
diff --git a/man/coredump.conf.xml b/man/coredump.conf.xml
index 3d325e6ad7..0b7329bf55 100644
--- a/man/coredump.conf.xml
+++ b/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="conf" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
 
   <refsect1>
     <title>Options</title>
diff --git a/man/journald.conf.xml b/man/journald.conf.xml
index 364b58f07e..85146b0d82 100644
--- a/man/journald.conf.xml
+++ b/man/journald.conf.xml
@@ -64,8 +64,7 @@
 
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
 
   <refsect1>
     <title>Options</title>
diff --git a/man/logind.conf.xml b/man/logind.conf.xml
index ffaec50351..ca2b18783c 100644
--- a/man/logind.conf.xml
+++ b/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="conf" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
 
   <refsect1>
     <title>Options</title>
diff --git a/man/resolved.conf.xml b/man/resolved.conf.xml
index 36cae2706c..8047a4ea75 100644
--- a/man/resolved.conf.xml
+++ b/man/resolved.conf.xml
@@ -63,8 +63,7 @@
 
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
 
   <refsect1>
     <title>Options</title>
diff --git a/man/standard-conf.xml b/man/standard-conf.xml
index b87d7e955b..36af45927d 100644
--- a/man/standard-conf.xml
+++ b/man/standard-conf.xml
@@ -33,13 +33,39 @@
     configuration file.</para>
   </refsection>
 
-  <refsection id='conf'>
-    <title>Configuration File</title>
-
-    <para>Configuration is also read from a single configuration file in
-    <filename>/etc/</filename>. This 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.</para>
+  <refsection id='main-conf'>
+    <title>Configuration Directories and Precedence</title>
+
+    <para>Default configuration is defined during compilation, so a
+    configuration file is only needed when it is necessary to deviate
+    from those defaults. By default the configuration file in
+    <filename>/etc/systemd/</filename> contains commented out entries
+    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>
diff --git a/man/systemd-sleep.conf.xml b/man/systemd-sleep.conf.xml
index 433f2f83a0..bb17ec8669 100644
--- a/man/systemd-sleep.conf.xml
+++ b/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="conf" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
 
   <refsect1>
     <title>Options</title>
diff --git a/man/systemd-system.conf.xml b/man/systemd-system.conf.xml
index 7c3f237567..c7bcfaee4d 100644
--- a/man/systemd-system.conf.xml
+++ b/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="conf" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
 
   <refsect1>
     <title>Options</title>
diff --git a/man/timesyncd.conf.xml b/man/timesyncd.conf.xml
index 1127970a18..89a651c662 100644
--- a/man/timesyncd.conf.xml
+++ b/man/timesyncd.conf.xml
@@ -63,8 +63,7 @@
 
   </refsect1>
 
-  <xi:include href="standard-conf.xml" xpointer="confd" />
-  <xi:include href="standard-conf.xml" xpointer="conf" />
+  <xi:include href="standard-conf.xml" xpointer="main-conf" />
 
   <refsect1>
     <title>Options</title>
diff --git a/src/bootchart/bootchart.conf b/src/bootchart/bootchart.conf
index 2d7cb61217..4f5e50936e 100644
--- a/src/bootchart/bootchart.conf
+++ b/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
-# /etc/systemd/bootchart.conf.d/*.conf.
+# Entries in this file show the compile time defaults.
+# 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
diff --git a/src/core/system.conf b/src/core/system.conf
index a3727200df..231609033b 100644
--- a/src/core/system.conf
+++ b/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
-# /etc/systemd/system.conf.d/*.conf.
+# Entries in this file show the compile time defaults.
+# 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
diff --git a/src/journal/coredump.conf b/src/journal/coredump.conf
index 0fe9fe801a..c2f0643e03 100644
--- a/src/journal/coredump.conf
+++ b/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
-# /etc/systemd/coredump.conf.d/*.conf.
+# Entries in this file show the compile time defaults.
+# 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
diff --git a/src/journal/journald.conf b/src/journal/journald.conf
index 29bdf8f183..47eefe91c1 100644
--- a/src/journal/journald.conf
+++ b/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
-# /etc/systemd/journald.conf.d/*.conf.
+# Entries in this file show the compile time defaults.
+# 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
diff --git a/src/login/logind.conf b/src/login/logind.conf
index 6b1943a2d1..834c4c2ebf 100644
--- a/src/login/logind.conf
+++ b/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
-# /etc/systemd/logind.conf.d/*.conf.
+# Entries in this file show the compile time defaults.
+# 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
diff --git a/src/resolve/resolved.conf.in b/src/resolve/resolved.conf.in
index e5a19ee474..3eb19e42b7 100644
--- a/src/resolve/resolved.conf.in
+++ b/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
-# /etc/systemd/resolved.conf.d/*.conf.
+# Entries in this file show the compile time defaults.
+# You can change settings by editing this file.
+# Defaults can be restored by simply deleting this file.
 #
 # See resolved.conf(5) for details
 
diff --git a/src/timesync/timesyncd.conf.in b/src/timesync/timesyncd.conf.in
index fc3c6c49cf..b6a2ada273 100644
--- a/src/timesync/timesyncd.conf.in
+++ b/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
-# /etc/systemd/timesyncd.conf.d/*.conf.
+# Entries in this file show the compile time defaults.
+# 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=