Chapter 8. Working with Permissions and Ownership

The dual concepts of permissions and ownership in Unix are not only an important part of Unix’s high level of stability—they are also the foundation for its system of security.

This chapter covers these two critical concepts, and from the very first we want to impress upon you the difference between them. Even Unix veterans are sometimes tripped up when they haven’t sufficiently separated the two concepts in their minds.

It’s really quite simple. Think “Who owns it?” and “What permission do they have?” Ownership in Unix deals with who controls something. Permissions deals with what the owners (and others) can do with something. Every file is “owned” by one user and one group. Every file has a set ...

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