-This can also be a colon separated list of directories to be searched for
-Kerberos credential files. The sequence "%U", if used, is replaced with
-the UID of the user for whom credentials are being searched.
-Note that if machine credentials are being
-stored in files, then the first directory on this list is where the
-machine credentials are stored.
+The literal sequence "%U" can be specified to substitue the UID
+of the user for whom credentials are being searched.
+.TP
+.B -M
+By default, machine credentials are stored in files in the first
+directory in the credential directory search path (see the
+.B -d
+option). When
+.B -M
+is set,
+.B rpc.gssd
+stores machine credentials in memory instead.