Network File System

NFS, or the Network File System, was originally developed by Sun Microsystems in the 1980's as a way to create a file system on diskless clients. NFS provides remote access to shared file systems across networks. This means that a file system may actually be sitting on machine A, but machine B can mount that filesystem and it will look to the users on machine B like the file system resides on the local machine. In this way NFS is transparent to the user. NFS was also designed to be machine, operating system, network architecture, and transport protocol independent.

The primary functions of NFS are to export or mount directories to other machines, either on or off a local network. These diretories can then be accessed as though they were local. NFS uses a client/server architecture and consists of a client program, a server program, and a protocol used to communicate between the two.

The server program makes filesystems available for access by other machines via a process called exporting. File systems that are available for access across the network are often referred to as shared file systems.

NFS clients access shared file systems mounting them from an NFS server machine. When a file system is mounted, it is integrated into the directory tree. An advanced form of this service is the automounter, which autmomatically mounts and unmounts file systems.

The NFS mount protocol facilitates the fucntions that allow NFS clients to attach remote directory trees to a mount point in the local file system. A mount point is an empty directory or subdirectory, created as place to attache a remote file system. In order to mount a file system from an NFS server, a user needs an account on the machine where the file system resides. The NFS client passes the UID and GID of the process requesting the mount to the NFS server. The server then validates the request. Mount protocol also allows the server to grant remote access privileges to a restricted set of clients via export control.

There are currently three versions of NFS. The default version for most workstations is NFS2, although IRIX 6.2 and Soloris 2.5.1 support NFS3.

For further essential information on NFS see Network File System and System Administration Using NFS.

For additional optional information on NFS protocol see NFS Protocol.