Appendix B: NFS Overview

What is NFS?

Example

Let's look at how NFS might be used in conjunction with the Alias software.

For this example, assume you have two SGI workstations -identical except that one, big, has lots of disk space, while the other, little, does not. By using NFS to mount /usr/aw/alias from big to little, you can save storage space on the smaller machine. In this example, big is acting as a disk server for little. Unless otherwise specified, all work must be done by root.

The file /etc/exports is used by NFS to determine what file systems can be networked (or exported) to other systems. First you have to determine which file system the Alias software was installed in. If you used the default installation then this will be /usr but it may be a different file system if you machine has more than one. To determine what file system the software was installed in run this command on big:

ls -l /usr/aw/alias

This will print out a line that will end in something like this:

/usr/aw/alias -> alias8.5

In this example the Alias software is installed in /usr. On big, edit /etc/exports and add the file system the Alias software was installed in. In the example of /usr you would add the following line to /etc/exports

/usr

and then tell NFS to export this file system by running the command:

/usr/etc/exportfs -a

The file /etc/fstab is used by IRIX when it mounts file systems. On little, edit /etc/fstab to add the following line:

big:/usr  /bigusr  nfs rw,soft,bg  0 0

This allows the /usr file system on big to be accessed from little using /bigusr. On little, create a directory on which big:/usr can be mounted, and mount it:

mkdir /bigusr

/etc/mount /bigusr

On little, verify that things are ok. Run df. You should see something similar to this:

Filesystem Type blocks use    avail %use Mounted on

big:/usr   nfs  175488 156525 18962 89%  /bigusr

On little, make /usr/aw/alias point to the Alias software on big.

mkdir /usr/aw




In -s /bigusr/aw/alias8.5 /usr/aw/alias

If the Alias software was installed in a file system other than /usr or the software is not installed in the top level of a directory (for example, /usr/u/aw/alias8.5) you will have to change the above commands accordingly.

Now proceed to set up your accounts as outlined in the Installation Notes.

Note

The file /var/flexlm/aw.dat must contain the appropriate license information on each machine for the Alias software to run. This example can be extended to additional workstations, with two conditions:

• First, a disk server and the network can handle a limited volume of traffic. There is no hard limit; it depends on your level of activity. If you see messages of the form:

NFS getattr failed for server big: RPC: Timed out




It means you have a network problem that could range 
from network overloading to hardware problems. 
Unfortunately, the Alias software in this NFS 
configuration relies on the server for its menus. When this 
type of error is encountered, the software must exit, but it 
will save your work in progress first.

• Another way in which NFS might be used is to place each user's home directory and work environment on one of the machines, and use NFS to make that area accessible to every workstation. (i.e, to mount it on every machine). Using this technique, a user may sign on at any available workstation, and still have immediate access to his or her files. We suggest that you undertake this strategy only if you have sufficient knowledge of IRIX system administration.