Linux Operating System and User Management

Linux is well known for its reliability, security, and flexibility in customization. One of its key features, like other Unix-based systems, is multi-user support.

This feature originated in the early days when Unix-based computers occupied entire rooms. A multi-user architecture was essential for allowing multiple individuals to use a single machine simultaneously while maintaining data and configuration isolation.

Today, this capability remains relevant, as servers, cloud services, and even personal computers are often used by multiple users. It ensures that each user can work independently without interfering with others while keeping their data secure.

In this guide, we will explain how to create a new user via the Linux terminal. Even if you’re a beginner, don’t worry—everything will be simple and clear.

What You Need to Know Before Starting

Administrator Privileges – To add new users, you need access to an account with superuser (sudo) rights.
Basic Commands – We will use useradd and passwd to create a user and set a password.

Step 1: Checking Default Settings

Before creating a new user, it’s useful to check the current default settings. Run the following command:

useradd -D

This will display parameters such as the default shell and home directory. You can modify these settings if needed.

Step 2: Creating a User

To add a new user, execute the following command:

sudo useradd -m username

The -m flag automatically creates the /home/username directory.
Replace username with your desired username.

Next, set a password:

sudo passwd username

The system will ask you to enter the password twice for verification.

Your new user is now ready to use!

Usage Examples

1. User with a Custom Home Directory

If you need to specify a non-standard home directory, use the -d flag:

sudo useradd -m -d /custom/path username

Then, set the password:

sudo passwd username

2. Temporary User with an Expiration Date

To create a user with an account that expires on October 1, 2025:

sudo useradd -m -e 2025-10-01 username

sudo passwd username

The -e flag sets the expiration date for the account.

3. System User Without a Home Directory

To create a system user without a personal home directory, use:

sudo useradd -r -M -s /bin/false -c "System User" username

-r creates a system user.
-M prevents the creation of a home directory.
-s /bin/false disables login access.
-c "System User" adds a description (visible in /etc/passwd).

System users are designed for background services and processes, such as:

mysql
nginx
www-data
sshd
backup

Useful Commands and Files

List all users:

cat /etc/passwd

Check password expiration:

sudo chage -l username

Now you know how to add users in Linux. If you have questions, consult the command manual using man useradd. Good luck!