To grant or restrict access to certain files and directories, the
chmod command can be used. This command stands for change mode and requires at least two parameters: the mode that needs to be applied and the file or directory on which this needs to be applied.
Managing permissions properly can be quite complex, though the manual page does help quite a bit. The basics are as follows. Under Linux, there are three standard access levels: user, group, and others. A fourth virtual-access level exists to cover the three others, all. Let us take a look at each of these in detail: