Configuring NFS on the Client

NFS configuration on the client requires you to start the NFS application; create a directory on which to mount the NFS server's directories that you exported via the /etc/exports file, and finally to mount the NFS server's directory on your local directory, or mount point. Here's how to do it all.

Starting NFS on the Client

Three more steps easily configure NFS on the client:

[root@smallfry tmp]# chkconfig --level 35 netfs on
[root@smallfry tmp]# chkconfig --level 35 nfslock on
[root@smallfry tmp]# chkconfig --level 35 portmap on

[root@smallfry tmp]# service portmap start
[root@smallfry tmp]# service netfs start
[root@smallfry tmp]# service nfslock start

[root@smallfry root]# rpcinfo  -p
   program vers proto    port
    100000    2    tcp     111  portmapper
    100000    2    udp     111  portmapper
    100024    1    udp   32768  status
    100024    1    tcp   32768  status
    100021    1    udp   32769  nlockmgr
    100021    3    udp   32769  nlockmgr
    100021    4    udp   32769  nlockmgr
    100021    1    tcp   32769  nlockmgr
    100021    3    tcp   32769  nlockmgr
    100021    4    tcp   32769  nlockmgr
    391002    2    tcp   32770  sgi_fam
[root@smallfry root]#

NFS and DNS

The NFS client must have a matching pair of forward and reverse DNS entries on the DNS server used by the NFS server. In other words, a DNS lookup on the NFS server for the IP address of the NFS client must return a server name that will map back to the original IP address when a DNS lookup is done on that same server name.

     [root@bigboy tmp]# host 192.168.1.102
     201.1.168.192.in-addr.arpa domain name pointer 192-168-1-102.my-web-
     site.org.
     [root@bigboy tmp]# host 192-168-1-102.my-web-site.org
     192-168-1-102.my-web-site.org has address 192.168.1.102
     [root@bigboy tmp]#

This is a security precaution added into the nfs package that lessens the likelihood of unauthorized servers from gaining access to files on the NFS server. Failure to correctly register your server IPs in DNS can result in "fake hostname" errors:

     Nov  7 19:14:40 bigboy rpc.mountd: Fake hostname smallfry.my-web-
     site.org for 192.168.1.1 - forward lookup doesn't exist

Making NFS Mounting Permanent

In most cases, users want their NFS directories to be permanently mounted. This requires an entry in the /etc/fstab file in addition to the creation of the mount point directory.

The /etc/fstab File

The /etc/fstab file lists all the partitions that need to be auto-mounted when the system boots. Therefore, you need to edit the /etc/fstab file if you need the NFS directory to be made permanently available to users on the NFS. For the example, mount the /data/files directory on server Bigboy (IP address 192.16801.100) as an NFS-type filesystem using the local /mnt/nfs mount point directory:

     #/etc/fstab
     #Directory                Mount Point    Type    Options      Dump
     FSCK
     192.168.1.100:/data/files /mnt/nfs       nfs     soft,nfsvers=2 0
     0

This example used the soft and nfsvers options; Table 29.1 outlines these and other useful NFS mounting options you may want to use. See the NFS man pages for more details.

Table 29.1. Possible NFS Mount Options

Option	Description
bg	Retry mounting in the background if mounting initially fails.
fg	Mount in the foreground.
soft	Use soft mounting.
hard	Use hard mounting.
rsize=n	The amount of data NFS will attempt to access per read operation. The default is dependent on the kernel. For NFS version 2, set it to 8192 to assure maximum throughput.
wsize=n	The amount of data NFS will attempt to access per write operation. The default is dependent on the kernel. For NFS version 2, set it to 8192 to assure maximum throughput.
nfsvers=n	The version of NFS the mount command should attempt to use,
tcp	Attempt to mount the filesystem using TCP packets; the default is UDP.
intr	If the filesystem is hard mounted and the mount times out, allow for the process to be aborted using the usual methods such as CTRL-C and the kill command.

The steps to mount the directory are fairly simple, as you'll see.

Permanently Mounting the NFS Directory

You'll now create a mount point directory, /mnt/nfs, on which to mount the remote NFS directory and then use the mount -a command to activate the mount. Notice how before mounting there were no files visible in the /mnt/nfs directory, this changes after the mounting is completed:

     [root@smallfry tmp]# mkdir /mnt/nfs
     [root@smallfry tmp]# ls /mnt/nfs
     [root@smallfry tmp]# mount -a
     [root@smallfry tmp]# ls /mnt/nfs
     ISO  ISO-RedHat  kickstart  RedHat
     [root@smallfry tmp]#

Each time your system boots, it reads the /etc/fstab file and executes the mount -a command, thereby making this a permanent NFS mount.

Note There are multiple versions of NFS, the most popular of which is version 2, which most NFS clients use. Newer NFS servers may also be able to handle NFS version 4. To be safe, it is best to force the NFS server to export directories as version 2 using the nfsvers=2 option in the /etc/fstab file as shown in the example. Failure to do so may result in an error message: [root@probe-001 tmp]# mount -a mount to NFS server '192.168.1.100' failed: server is down. [root@probe-001 tmp]#

Manually Mounting NFS File Systems

If you don't want a permanent NFS mount, then you can use the mount command without the /etc/fstab entry to gain access only when necessary. This is a manual process; for an automated process, see the section "The NFS automounter."

In this case, you're mounting the /data/files directory as an NFS-type filesystem on the /mnt/nfs mount point. The NFS server is Bigboy whose IP address is 192.168.1.100.

Notice how before mounting there were no files visible in the /mnt/nfs directory, this changes after the mounting is complete:

     [root@smallfry tmp]# mkdir /mnt/nfs
     [root@smallfry tmp]# ls /mnt/nfs
     [root@smallfry tmp]# mount -t nfs 192.168.1.100:/data/files /mnt/nfs
     [root@smallfry tmp]# ls /mnt/nfs
     ISO  ISO-RedHat  kickstart  RedHat
     [root@smallfry tmp]#

Congratulations! You've made your first steps towards being an NFS administrator.