A user account is required when using Linux. By giving the user the authority to use the Linux system, it is possible to manage the authority to browse and edit files and directories, arbitrary programs and shell scripts, and the authority to execute.
The minimum unit of privilege to operate resources such as memory and files.
For handling the privileges of multiple users at once. The user always belongs to one or more groups, and the group to which the user belongs is called a primary group.
A special user with unlimited usage. You can change the system, install and remove programs, and create and remove users. Since all users can access directories and read / write contents regardless of access rights, it is necessary to strictly manage them.
A command that allows a logged-in user to temporarily become another user. If you execute it without specifying a user, it becomes the root user. If multiple people are used as the root user, only the history of the root user remains in the history, so it is difficult to know who did what. When switching from a general user to the root user, the time when the work was started as the root user remains.
You can execute commands with superuser (root) privileges. Settings and programs can be executed with root privileges without switching users with the su command.