Security Strategies in Linux Platforms and Applications, 3rd Edition

Protecting Files with Ownership, Permissions, and Access Controls

Everything on Linux is represented by a file. A directory is a special kind of file, which should be executable for users who are allowed to list files on that directory. If the execute permission isn’t set, you won’t be able to change into that directory using the cd command. Other special kinds of files include devices, commonly used to represent and communicate with certain hardware components; character devices such as sound cards; block devices such as drives and partitions; and soft links, which can connect files across different partitions or volumes.

Every file and directory on a Linux system is owned by a specific user and group. With discretionary access controls, the ...