needed for NFS4.
    see:
    http://lists.centos.org/pipermail/centos/2009-July/078775.html
    http://www.novell.com/support/kb/doc.php?id=7005060
    http://pic.dhe.ibm.com/infocenter/zos/v1r12/index.jsp?topic=%2Fcom.ibm.zos.r12.idan400%2Fkerlinx.htm