Installing and Getting Started with Docker on Linux: A Comprehensive Guide for Beginners

Introduction

Docker is a revolutionary platform that simplifies building, shipping, and running applications in lightweight containers. This guide provides clear, step-by-step instructions for installing Docker on Linux distributions (Ubuntu/Debian/CentOS) and running your first container. No prior Docker experience required!

🛠 Prerequisites

1. Linux System: Ubuntu 20.04+, Debian 10+, or CentOS 7+
2. Terminal Access: Use Ctrl+Alt+T (Ubuntu/Debian) or connect via SSH.
3. Admin Privileges: Run commands with sudo.
4. Internet Connection: Required for downloads.

🔄 Step 1: Remove Old Docker Versions

Ensure a clean installation:

sudo apt-get remove docker docker-engine docker.io containerd runc  # Ubuntu/Debian

sudo yum remove docker docker-client docker-common docker-latest  # CentOS

⬇️ Step 2: Install Docker

For Ubuntu/Debian:

1. Update packages:

   sudo apt-get update

2. Install dependencies:

   sudo apt-get install apt-transport-https ca-certificates curl gnupg

3. Add Docker’s GPG key:

   curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

4. Set up the repository:

   echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

5. Install Docker Engine:

   sudo apt-get update && sudo apt-get install docker-ce docker-ce-cli containerd.io

For CentOS:

1. Install dependencies:

   sudo yum install -y yum-utils

2. Add Docker repository:

   sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

3. Install Docker Engine:

   sudo yum install docker-ce docker-ce-cli containerd.io

▶️ Step 3: Start Docker

Enable and launch the Docker service:

sudo systemctl start docker          # Start Docker
sudo systemctl enable docker         # Launch on boot
sudo systemctl status docker         # Verify it's running

✅ Step 4: Verify Installation

Run a test container:

sudo docker run hello-world

✅ Expected Output:

Hello from Docker!  
This message shows your installation works correctly.

👥 Step 5: Run Docker as Non-Root User (Optional but Recommended)

Avoid using sudo with Docker:

sudo usermod -aG docker $USER    # Add your user to the "docker" group
newgrp docker                    # Apply group changes immediately

🔑 Important: Log out and back in for changes to take effect.

🐳 Step 6: Basic Docker Commands

🚀 Example: Run a Web Server

1. Start an Nginx container:

   docker run -d --name my-web -p 8080:80 nginx

2. Access in your browser:
   http://:8080 → Welcome to Nginx!

🔧 Troubleshooting

• Permission Denied? Ensure your user is in the docker group (Step 5).
• “hello-world” not working? Check internet connectivity and Docker service status (systemctl status docker).
• Firewall Issues: Allow Docker ports (e.g., sudo ufw allow 8080 on Ubuntu).

📌 Conclusion

You’ve successfully installed Docker, run your first container, and learned essential commands! Docker streamlines application deployment—explore Docker Hub for pre-built images (MySQL, Python, etc.).

> Next Steps:
> – Learn Dockerfile basics to create custom images.
> – Try Docker Compose for multi-container apps.
> – Check the official Docker docs for advanced topics!

💬 Questions? Share them in the comments below!