Understanding Users in Linux: Who’s Using the System?

A user in Linux is someone who logs into the system and has a unique identity that determines what they can do, what files they own, and what resources they can access. There are two types of users in Linux: system users and normal users. System users are created automatically during installation and are used by the system and background services, while normal users are actual human users who log in to do work. Linux identifies users using a unique User ID (UID) assigned to every account. UIDs range from 0 to 999 for system users and from 1000 to 60000 for normal users. User information is stored in special configuration files, including /etc/passwd and /etc/shadow. The /etc/passwd file stores general user information, while the /etc/shadow file stores password-related information in an encrypted format. Essential user management commands include useradd to create a new user, passwd to set or change a password, and userdel to delete a user account. User data can be checked using the grep command, and users can switch to another user account using the su command. Understanding user management is crucial in Linux, and mastering these concepts and commands is essential for effective system administration.