NFS - Network File System
With UNIX, all the disk storage on a given computer is organised into a single inverted-tree directory structure. The top directory, which contains all other sub-directories and files, is called the root and is represented by a /. The root directory is based on the machine's first disk drive. It is divided into sub-directories.
The user sees this directory structure as the neat seamless tree, but in fact, it may be spread over several disks on his own workstation, plus some storage on a host connected via the local area network. The df command produces a report that reveals the physical disks on which the various sub-directories are really stored:
File System Mount Point
This says that the user's root directory is on the workstation's own disk sd0a, his usr sub-directory is on disk sd0g, his home directory is on disk sd0f and his tmp directory is on drive sd3a. In NFS terms, sub-directory /usr is said to be the mount point for disk sd0g, /home is said to be the mount point for disk sd0f and /tmp is said to be the mount point for disk sd3a. The local directory structure with the mounting points of the various local disks is shown below:
Sub-directory mail under the local parent sub-directories /var/spool is located on another machine on the network whose name is eustace. The same is true for the news sub-directories under their parent sub-directories /usr/spool and /usr/lib respectively. Eustace's directory /usr/spool/mail is said to be mounted at sharon's /usr/spool/mail and similarly for /usr/spool/news and /usr/lib/news.
NFS is susceptible to other machines crashing and being re-started. It cannot handle the simultaneous updating of files by different users very well. It cannot handle server crashes. Other remote file systems are RFS, AFS and Novell Netware.
© 1998 Robert John Morton