The Network File System (NFS) is a service that provides network accessible file systems for client machines. Refer to Chapter 19, Network File System (NFS) for more information about NFS. The following subsections assume a basic knowledge of NFS.
The version of NFS included in Red Hat Enterprise Linux, NFSv4, no longer requires the portmap service as outlined in Section 43.2.2, “Securing Portmap”. NFS traffic now utilizes TCP in all versions, rather than UDP, and requires it when using NFSv4. NFSv4 now includes Kerberos user and group authentication, as part of the RPCSEC_GSS kernel module. Information on portmap is still included, since Red Hat Enterprise Linux supports NFSv2 and NFSv3, both of which utilize portmap.