man: document automatic dependencies

For all units ensure there's an "Automatic Dependencies" section in the
man page, and explain which dependencies are automatically added in all
cases, and which ones are added on top if DefaultDependencies=yes is
set.

This is also done for systemd.exec(5), systemd.resource-control(5) and
systemd.unit(5) as these pages describe common behaviour of various unit
types.

1 files changed, 42 insertions, 4 deletions

diff --git a/man/systemd.socket.xml b/man/systemd.socket.xml
index 410886f841..beac053bf0 100644
--- a/man/systemd.socket.xml
+++ b/man/systemd.socket.xml
@@ -134,6 +134,40 @@
   </refsect1>
 
   <refsect1>
+    <title>Automatic Dependencies</title>
+
+    <para>Socket units automatically gain a <varname>Before=</varname>
+    dependency on the service units they activate.</para>
+
+    <para>Socket units referring to file system paths (such as AF_UNIX
+    sockets or FIFOs) implicitly gain <varname>Requires=</varname> and
+    <varname>After=</varname> dependencies on all mount units
+    necessary to access those paths.</para>
+
+    <para>Socket units using the <varname>BindToDevice=</varname>
+    setting automatically gain a <varname>BindsTo=</varname> and
+    <varname>After=</varname> dependency on the device unit
+    encapsulating the specified network interface.</para>
+
+    <para>If <varname>DefaultDependencies=yes</varname> is set (the
+    default), socket units automatically gain a
+    <varname>Before=</varname> dependency on
+    <filename>sockets.target</filename>. They also gain a pair of
+    <varname>After=</varname> and <varname>Requires=</varname>
+    dependency on <filename>sysinit.target</filename>, and a pair of
+    <varname>Before=</varname> and <varname>Conflicts=</varname>
+    dependencies on <filename>shutdown.target</filename>. These
+    dependencies ensure that the socket unit is started before normal
+    services at boot, and is stopped on shutdown.</para>
+
+    <para>Additional implicit dependencies may be added as result of
+    execution and resource control parameters as documented in
+    <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+    and
+    <citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+  </refsect1>
+
+  <refsect1>
     <title>Options</title>
 
     <para>Socket files must include a [Socket] section, which carries
@@ -309,12 +343,14 @@
         <listitem><para>Specifies a network interface name to bind
         this socket to. If set, traffic will only be accepted from the
         specified network interfaces. This controls the
-        SO_BINDTODEVICE socket option (see
-        <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
+        SO_BINDTODEVICE socket option (see <citerefentry
+        project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>
         for details). If this option is used, an automatic dependency
         from this socket unit on the network interface device unit
         (<citerefentry><refentrytitle>systemd.device</refentrytitle><manvolnum>5</manvolnum></citerefentry>
-        is created.</para></listitem>
+        is created. Note that setting this parameter might result in
+        additional dependencies to be added to the unit (see
+        above).</para></listitem>
       </varlistentry>
 
       <varlistentry>
@@ -719,7 +755,9 @@
         with <varname>Accept=no</varname>. It defaults to the service
         that bears the same name as the socket (with the suffix
         replaced). In most cases, it should not be necessary to use
-        this option.</para></listitem>
+        this option. Note that setting this parameter might result in
+        additional dependencies to be added to the unit (see
+        above).</para></listitem>
       </varlistentry>
 
       <varlistentry>