Starting And Stopping Nfs - Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual

version by the kernel and mount command. This option is not supported with NFSv4 and should not
be used.
• noacl — Turns off all ACL processing. This may be needed when interfacing with older versions of
Red Hat Enterprise Linux, Red Hat Linux, or Solaris, since the most recent ACL technology is not
compatible with older systems.
• nolock — Disables file locking. This setting is occasionally required when connecting to older NFS
servers.
• noexec — Prevents execution of binaries on mounted file systems. This is useful if the system is
mounting a non-Linux file system via NFS containing incompatible binaries.
• nosuid — Disables set-user-identifier or set-group-identifier bits. This prevents remote users from
gaining higher privileges by running a setuid program.
• port=num — Specifies the numeric value of the NFS server port. If num is 0 (the default), then
mount queries the remote host's portmapper for the port number to use. If the remote host's NFS
daemon is not registered with its portmapper, the standard NFS port number of TCP 2049 is used
instead.
• rsize=num and wsize=num — These settings speed up NFS communication for reads (rsize)
and writes (wsize) by setting a larger data block size, in bytes, to be transferred at one time. Be
careful when changing these values; some older Linux kernels and network cards do not work well
with larger block sizes. For NFSv2 or NFSv3, the default values for both parameters is set to 8192.
For NFSv4, the default values for both parameters is set to 32768.
• sec=mode — Specifies the type of security to utilize when authenticating an NFS connection.
sec=sys is the default setting, which uses local UNIX UIDs and GIDs by means of AUTH_SYS to
authenticate NFS operations.
sec=krb5 uses Kerberos V5 instead of local UNIX UIDs and GIDs to authenticate users.
sec=krb5i uses Kerberos V5 for user authentication and performs integrity checking of NFS
operations using secure checksums to prevent data tampering.
sec=krb5p uses Kerberos V5 for user authentication, integrity checking, and encrypts NFS traffic
to prevent traffic sniffing. This is the most secure setting, but it also has the most performance
overhead involved.
• tcp — Specifies for the NFS mount to use the TCP protocol.
• udp — Specifies for the NFS mount to use the UDP protocol.
Many more options are listed on the mount and nfs man pages.

19.5. Starting and Stopping NFS

To run an NFS server, the portmap service must be running. To verify that portmap is active, type
the following command as root:
/sbin/service portmap status
Starting and Stopping NFS
249