File and Directory Permissions
As I stated in the introduction to this chapter, file and directory permissions are the basics for providing security on a system. These, along with the authentication system, provide the basis for all security. Unfortunately, many people do not know what permissions on directories mean, or they assume that permissions mean the same thing they do on files. The following section describes the permissions on files; after that, the permissions on directories are described.
The permissions for files are split into three sections: the owner of the file, the group associated with the file, and everyone else (the world). Each section has its own set of file permissions, which provide the ability to read, write, and ...