Mastering Linux Security and Hardening - Second Edition

Using chmod to set permissions on files and directories

On Unix and Linux systems, you would use the chmod utility to set permissions values on files and directories. You can set permissions for the user of the file or directory, the group that's associated with the file or directory, and more. The three basic permissions are as follows:

• r: This indicates a read permission.
• w: This indicates a write permission.
• x: This is the executable permission. You can apply it to any type of program file, or to directories. If you apply an executable permission to a directory, authorized people will be able to cd into it.

If you perform ls -l on a file, you'll see something like this:

-rw-rw-r--. 1 donnie donnie     804692 Oct 28 18:44 yum_list.txt

The ...