adds a note

xml/security_kerberos.xml

@@ -2042,6 +2042,11 @@ The trace log captures the process details.
                 </variablelist>
        </step>
    </procedure>
+   <note><para>Machine accounts are subject to the same &krb; authentication as user accounts.
+    During &krb; authentication, clients that run local processes using the <literal>system</literal>
+account, assign these processes to the machine account when accessing remote resources. The machine account
+is associated to the computer name registered with the domain controller and is distinct with a <literal>$</literal>
+sign.</para></note>
     </sect1>
  <sect1 xml:id="sec-security-kerberos-nfs">
   <title>&krb; and NFS</title>