User Management in Linux: A Comprehensive Guide

Managing users in Linux is a fundamental aspect of system administration. Effective user management ensures that only authorized individuals can access the system and perform specific tasks, enhancing security and maintaining order in a multi-user environment. This tutorial will guide you through the essential concepts and commands for managing users in Linux.

Understanding User Types in Linux

• Root User: The root user is the superuser with complete control over the system. It can perform any action, including modifying critical system files.
• Regular Users: These are non-privileged users with limited permissions, typically used for day-to-day operations.
• System Users: These accounts are used by system services and daemons. They usually do not have a home directory or shell access.

User Management Files

• /etc/passwd: Contains user account information such as username, UID, GID, home directory, and default shell.
• /etc/shadow: Stores password information, including password hashes and password expiration details.
• /etc/group: Defines the groups to which users belong, along with GID and group members.

Creating a New User

To create a new user, use the useradd command:

sudo adduser username        

check/identify user

to check existence of user within a system

id username        

Deleting a User

To delete a user, use the userdel command:

sudo userdel username        

If you want to remove the user’s home directory along with the account:

sudo userdel -r username        

Change user in Terminal

Change user while staying at terminal:

su username        

Exit from self account:

exit        

Change password

change password for self account:

passwd        

Change password for another user:

sudo passwd username        

Sudo user managing

Add a user into sudo group:

sudo usermod -aG sudo username        

Remove a user from sudo group:

sudo gpasswd -d username sudo