Each process running on our system is started by a user, to whom it belongs. Access to different files and directories by running processes is determined by the user associated with that process. Similarly, every file in our system is owned by some user and access to different files and directories on the system is restricted by user privileges. By default, new files created are owned by the user creating the file.

There are generally three types of user account in Linux systems:

• Root user (administrator)
• System users (used by various services)
• Regular users (normal users who carry out daily operations)