Group Management

Introduction

Linux is a multi-user operating system. This means multiple people can log in and use the same computer simultaneously. To maintain security, Linux uses Users and Groups to control who can read, write, or execute specific files.

The Root User

The root user (also known as the superuser) has absolute power over the entire system. They can modify any file, delete any user, and open any network port.

You should never log in directly as root. Instead, log in as a standard user and use the sudo (SuperUser DO) command to temporarily elevate your privileges for specific tasks.

User Management Commands

Adding a User

You can create a new user account using the useradd or adduser commands (the latter is more interactive and user-friendly on Debian/Ubuntu systems).

sudo adduser charlie

This command creates the user, prompts you for a password, and creates a home directory /home/charlie.

Modifying a User

The usermod command modifies existing user accounts. For example, to grant a standard user administrative privileges, you add them to the sudo group.

# Add charlie to the sudo group (the -aG flags mean Append to Group)
sudo usermod -aG sudo charlie

Deleting a User

Use the userdel command to remove an account.

# Delete the user charlie and remove their home directory
sudo userdel -r charlie

Group Management

Groups allow you to organize users and assign permissions to multiple people at once. For example, you might create a developers group and give that group write access to the /var/www/ web directory.

# Create a new group
sudo groupadd developers

# Add a user to the group
sudo usermod -aG developers alice

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