Chapter 6. Filesystems and Security

Filesystems control the way that information is stored on mass storage devices. Modern filesystems allow information to be stored in files with arbitrary names; these files are then arranged in a structured tree of directories and subdirectories. Most filesystems allow files to be created, deleted, modified, and moved to different directories. The whole task is somewhat complex, because filesystems allow character-by-character control over data, whereas most mass storage systems allow information to be read or written only block by block.

The filesystem is also the primary tool for enforcing security on a Unix system. Besides holding the computer's operating system, programs, and user data, additional information stored in the filesystem is used to determine what information can be viewed, what can be modified, and what is inaccessible to the various users and system processes.