Docker Installation on Ubuntu Server: A Complete Guide

Why Install Docker Manually?

While Docker provides convenience scripts, understanding the manual installation process gives you better control and insight into how Docker integrates with your Ubuntu system. This guide walks through the official installation method that's production-ready and idempotent—meaning you can safely repeat these steps without breaking anything.

Prerequisites

Before we begin, make sure you have:

Ubuntu server (18.04, 20.04, 22.04, or later)
Root or sudo access
Internet connection for package downloads

Step 1: Check Existing Installation

First, let's see if Docker is already installed on your system:

docker --version
docker compose version
systemctl status docker

If Docker is already installed, running, and you're in the docker group, you can skip ahead. Otherwise, let's proceed with a fresh installation.

Step 2: Clean Up Old Installations

Remove any conflicting Docker packages that might be present:

sudo apt remove -y docker docker-engine docker.io containerd runc

This ensures a clean slate and prevents package conflicts during installation.

Step 3: Install Prerequisites

Update your package index and install the necessary tools:

sudo apt update -y
sudo apt install -y ca-certificates curl gnupg lsb-release

These packages are required for:

ca-certificates: Verify SSL certificates when downloading packages
curl: Download files from the internet
gnupg: Manage GPG keys for package verification
lsb-release: Detect your Ubuntu version automatically

Step 4: Add Docker's GPG Key

Docker signs its packages to ensure authenticity. Let's add their official GPG key:

sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg

This downloads Docker's public key and stores it in a format APT can use for package verification.

Step 5: Configure Docker Repository

Add Docker's official APT repository to your system:

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

This command:

Detects your system architecture automatically
Links to the GPG key for verification
Uses lsb_release to detect your Ubuntu version
Updates the package list with Docker packages

Step 6: Install Docker Engine

Now install Docker and all its components:

sudo apt install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

This installs:

docker-ce: Docker Engine (Community Edition)
docker-ce-cli: Command-line interface
containerd.io: Container runtime
docker-buildx-plugin: Advanced build features
docker-compose-plugin: Docker Compose v2

Step 7: Configure User Permissions

By default, Docker requires sudo for every command. Add your user to the docker group:

sudo usermod -aG docker $USER

Important: You must log out and log back in for this change to take effect. Alternatively, run:

newgrp docker

This creates a new shell session with the updated group membership.

Step 8: Enable Docker Service

Ensure Docker starts automatically on system boot:

sudo systemctl enable docker
sudo systemctl start docker

Check the service status:

sudo systemctl status docker

You should see active (running) in the output.

Step 9: Verify Installation

Test that everything is working correctly:

# Check Docker version
docker --version
 
# Check Docker Compose version
docker compose version
 
# Run a test container
docker run hello-world

The hello-world container will download, run, print a success message, and exit. If you see the success message, Docker is working perfectly!

Troubleshooting

Permission Denied Error

If you get permission denied when running Docker commands:

Verify you're in the docker group: groups
If not, ensure you logged out and back in after Step 7
Or use newgrp docker to refresh your session

Service Won't Start

Check for errors:

sudo systemctl status docker
sudo journalctl -u docker.service

Common issues:

Port conflicts with existing services
Missing dependencies
Corrupted installation (try removing and reinstalling)

Docker Compose Command Not Found

If docker compose doesn't work but docker-compose does, you might have the old standalone version. The plugin uses docker compose (space, not hyphen).

What's Next?

Now that Docker is installed, you can:

Learn about Docker images and containers
Create your first Dockerfile
Explore Docker Compose for multi-container applications
Set up Docker volumes for persistent data

Conclusion

You now have a production-ready Docker installation on Ubuntu! This manual process gives you full control over Docker's configuration and helps you understand each component. The installation is idempotent, so you can safely re-run these steps if needed without breaking your system.

Remember to keep Docker updated with regular apt update && apt upgrade commands, and always test new Docker versions in a development environment before deploying to production.

Happy containerizing!