Basic NFS Setup

NFS allows one machine to access files on another machine. NFS has its origins in UNIX, but today appears in most operating systems, including those from Microsoft and Apple. OpenBSD supports NFS versions 1 through 3 as both a client and a server.

Entire books can be—and have been—written about NFS. We won’t go into the intimate details of NFS, but rather focus on getting a basic NFS share working on OpenBSD. Configuring NFS the first time can be intimidating, but after setting up a file share or two, you’ll find it straightforward.

If you have a complicated NFS environment—involving multiple versions of multiple operating systems—or if you want to share a directory among hundreds of active clients, you should do further research, but even a basic setup will help to simplify parts of your job.

NFS works on the client/server model. One computer, the server, offers filesystems to other computers. The server is exporting a filesystem, and the filesystems on offer are called exports. NFS clients can mount exports in a manner almost identical to that used to mount local filesystems.

One important thing to remember about NFS is that it is stateless, which means that NFS does not track the condition of a connection. You can reboot an NFS server, and the client won’t throw a fit. The client cannot access files on the server while the server is down, but once the server returns, the client will pick up right where things left off. Other network filesystems are not always so resilient. Statelessness causes its own problems as well. For example, clients cannot know when a file they are currently reading has been modified by another client.

If you’re just learning NFS (or OpenBSD’s implementation of NFS), check /var/log/messages for NFS-related error messages. If you’ve repeatedly reconfigured your NFS server as part of learning, and things just don’t work correctly, reboot your NFS server and/or client. NFS is complicated, and sometimes starting with a clean stack clears up a lot of problems. Once you understand how all the pieces fit together, a reboot to resolve problems should never be necessary.