Exporting Nfs File Systems - Red Hat ENTERPRISE LINUX 3 System Administration Manual

Chapter 23. Network File System (NFS)
23.2.3. Using TCP
The default transport protocol for NFS is UDP; however, the Red Hat Enterprise Linux 3 kernel
includes support for NFS over TCP. To use NFS over TCP, include the
mounting the NFS-exported file system on the client system. For example:
mount -o tcp shadowman.example.com:/misc/export /misc/local
If the NFS mount is specified in
server:/usr/local/pub
If it is specified in an autofs configuration file:
myproject -rw,soft,intr,rsize=8192,wsize=8192,tcp penguin.example.net:/proj52
Since the default is UDP, if the
cessed via UDP.
The advantages of using TCP include the following:
Improved connection durability, thus less
•
Performance gain on heavily loaded networks because TCP acknowledges every packet, unlike
•
UDP which only acknowledges completion.
TCP has better congestion control than UDP (which has none). On a very congested network, UDP
•
packets are the first types of packet that are dropped. Which means if NFS is writing data (in 8K
chunks) all of that 8K has to retransmitted. With TCP because of its reliability, one parts of that 8K
data is transmitted at a time.
Error detection. When a tcp connection breaks (due to the server going down) the client stops
•
sending data and starts the reconnection process. With UDP, since its connection-less, the client
continue to pound the network with data until server comes up.
The main disadvantage is that there is a very small performance hit due to the overhead associated
with the TCP protocol.
23.2.4. Preserving ACLs
The Red Hat Enterprise Linux 3 kernel provides ACL support for the ext3 file system and ext3 file
systems mounted with the NFS or Samba protocols. Thus, if an ext3 file system has ACLs enabled for
it and is NFS exported, if the NFS client can read ACLs, they are used by the NFS client as well.
For more information
Chapter 8 Access Control Lists.

23.3. Exporting NFS File Systems

Sharing files from an NFS server is known as exporting the directories. The NFS Server Configura-
tion Tool can be used to configure a system as an NFS server.
To use the NFS Server Configuration Tool, you must be running the X Window System, have root
privileges, and have the
Main Menu Button (on the Panel) => System Settings => Server Settings => NFS, or type the
command
redhat-config-nfs
/etc/fstab
/pub nfs
option is not specified, the NFS-exported file system is ac-
-o tcp
NFS stale file handles
about mounting
redhat-config-nfs
.
:
rsize=8192,wsize=8192,timeo=14,intr,tcp
NFS file systems
RPM package installed. To start the application, select
option to
-o tcp mount
messages.
with ACLs,
165
when
refer to