EP7: Users and Groups in RHEL

🎯 Introduction

In this tutorial, we’ll learn how to create users and groups in RHEL, a key topic in RHCSA (Red Hat Certified System Administrator) certification. You’ll understand not just the commands, but also the real-world purpose of users and groups — using simple examples.

Let’s get started!

👤 Why Do We Create Users and Groups?

Imagine Linux as an office building:

Users are the employees — each person needs their own login and workspace.
Groups are departments — like “Sales” or “IT”, which control shared access to resources.

So, in RHEL, users and groups help us manage:

Who can access what
Who owns which files
Who can run specific commands

🧑‍💻 1. Creating a User

✅ Basic Command:

sudo useradd <username>

✅ Example:

sudo useradd alice

This creates a new user named alice.

🔎 Behind the scenes: This command updates /etc/passwd, creates a home directory (if default settings apply), and assigns a UID.

🔒 Set a Password:

sudo passwd alice

The system will prompt you to enter and confirm a password.

👨‍👩‍👧 2. Creating a Group

✅ Basic Command:

sudo groupadd <groupname>

✅ Example:

sudo groupadd developers

This creates a new group named developers.

👥 3. Add a User to a Group

There are two types of group membership:

Primary group (only one per user)
Secondary group(s) (can be multiple)

✅ Change Primary Group:

sudo usermod -g <groupname> <username>

Example:

sudo usermod -g developers alice

Now, developers is the main group for alice.

✅ Add to Secondary Group:

sudo usermod -aG <groupname> <username>

Example:

sudo usermod -aG wheel alice

Now alice is also a member of the wheel group (used for sudo/root access).

⚠️ Important: Always use the -a (append) option with -G, or you’ll overwrite all existing secondary groups.

📁 4. Create User with Group in One Command

sudo useradd -g developers -G wheel alice

This:

Sets developers as the primary group
Adds alice to the wheel group as secondary

Set password as usual:

sudo passwd alice

🔍 5. View User & Group Information

Check user's group membership:

groups alice

View user account info:

id alice

View group details:

getent group developers

🧹 6. Delete User or Group

Delete user (keep files):

sudo userdel alice

Delete user (and home directory):

sudo userdel -r alice

Delete group:

sudo groupdel developers

⚠️ Make sure no user is using the group before deleting.

✅ Summary / Key Takeaways

Task	Command
Create user	`sudo useradd <username>`
Set password	`sudo passwd <username>`
Create group	`sudo groupadd <groupname>`
Set primary group	`sudo usermod -g <group> <user>`
Add to secondary group	`sudo usermod -aG <group> <user>`
View groups	`groups <user>`
Delete user	`sudo userdel [-r] <user>`
Delete group	`sudo groupdel <group>`

🎬 Final Thoughts

That’s it! You’ve just learned the essential commands and concepts for managing users and groups in RHEL — a skill you’ll use daily as a Linux sysadmin.

🗂 Think of users and groups as your access control system, helping you organize and secure your Linux environment.