Add another example on how to use dump over ssh, setting RSH=ssh.

svn path=/head/; revision=19668

en_US.ISO8859-1/books/handbook/disks/chapter.sgml

@@ -1786,6 +1786,17 @@ sa0(ncr1:4:0):  Logical unit is in process of becoming ready</screen>
           targetuser@targetmachine.example.com dd of=/mybigfiles/dump-usr-l0.gz</userinput></screen>
 
       </example>
+
+      <para>Or using <command>dump</command>'s built-in method,
+        setting the enviroment variable <envar>RSH</envar>:</para>
+
+      <example>
+	<title>Using <command>dump</command> over <application>ssh</application> with <envar>RSH</envar> set</title>
+
+	<screen>&prompt.root; <userinput>RSH=/usr/bin/ssh /sbin/dump -0uan -f targetuser@targetmachine.example.com:/dev/sa0</userinput></screen>
+
+      </example>
+
     </sect2>
 
     <sect2>