2 The Basis

A “normal” Linux file system has some basic tools for file and directory access control:

• Ownership: who owns the file, and hence has access to the file.
• Permissions: what kind of access is granted to an owner of a file?
• Groups: a group can have any number of users as members. This provides a mechanism to grant access to a select group of users instead of a single user or every user.

Given these basic tools, however, it is up to an administrator or end user to determine how to protect specific files and directories. This task can seem difficult for beginners. This module explains a systematic way to solve problems regarding file and directory access control.