How do file permissions work?

Question

Can you explain briefly the main concepts and command line tools used to manage file permissions?

Answer 1

Each file has rights for three different categories:

• the owner of the file,
• the group associated with the file, and
• everybody else.

Rights mean the right to read the file, the right to write to the file, or the right to execute the file in case of a script or program.

On the CLI, you may

• change the owner with chown, e.g. chown guillermooo
• change the group with chgrp, e.g. chgrp root
• change the rights with chmod, e.g. chmod u+w filename.ext (Adds writing permission for the owner of the file filename.ext)

If you'd like to know more about each of these tools, open a terminal and type man [tool], e.g. man chmod.

Answer 2

Here's a nice tutorial on it: http://www.elated.com/articles/understanding-permissions/