- <para>If -DDISABLE_SYSTEMD is set during compilation
- this function will always return 0 and otherwise
- become a NOP.</para>
+ <para>If the reference implementation is used as
+ drop-in files and -DDISABLE_SYSTEMD is set during
+ compilation these functions will always return 0 and
+ otherwise become a NOP.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Environment</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><varname>$NOTIFY_SOCKET</varname></term>
+
+ <listitem><para>Set by the init system
+ for supervised processes for status
+ and start-up completion
+ notification. This environment variable
+ specifies the socket
+ <function>sd_notify()</function> talks
+ to. See above for details.</para></listitem>
+ </varlistentry>
+ </variablelist>