+.TP
+.B \-g " or " \-\-manage-gids
+Accept requests from the kernel to map user id numbers into lists of
+group id numbers for use in access control. An NFS request will
+normally (except when using Kerberos or other cryptographic
+authentication) contains a user-id and a list of group-ids. Due to a
+limitation in the NFS protocol, at most 16 groups ids can be listed.
+If you use the
+.B \-g
+flag, then the list of group ids received from the client will be
+replaced by a list of group ids determined by an appropriate lookup on
+the server. Note that the 'primary' group id is not affected so a
+.I newgroup
+command on the client will still be effective. This function requires
+a Linux Kernel with version at least 2.6.21.