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Chapter 2: Getting Started on a UNIX System
The standard UNIX file system is a hierarchy of directories descending from what is known as the root directory. UNIX allows parts of the directory hierarchy, also called file systems, to reside on separate storage devices or in separate disk partitions. These are accommodated by means of mount points. A mount point is a directory in a file system that corresponds to the root directory of some other file system. The primary file system is the one starting at the true root. The standard UNIX file system is described in Chapter 6.
If the UNIX machine that you work on is part of an integrated system of UNIX machines, for example a LAN (local area network), it is likely that a distributed file serving system has been installed on it. A distributed file system provides a common directory structure and thus the same view of the file system to all participating nodes. This overrides the standard UNIX file system.
Fermilab is using the AFS (Andrew File System) as a distributed file service model, and it is installed on several machines at Fermilab in a production environment, including the FNALU cluster. See Chapter 7 for a discussion of AFS.
A special note to CDF and D0 users: Your UNIX systems are not configured to use AFS.