The Network File System, or NFS, is service that provides network accessible file systems for client machines. For more information on how NFS works, refer to the chapter titled Network File System (NFS) in the Red Hat Enterprise Linux Reference Guide. For more information about configuring NFS, refer to the Red Hat Enterprise Linux System Administration Guide. 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 5.2, “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 which utilize it.