Installing Docker on Ubuntu

Docker is a powerful platform for building, sharing, and running containerized applications. This guide walks you through a complete installation of Docker Engine on Ubuntu using Docker’s official repositories, including important post-installation steps to ensure everything works correctly.

Step 1: Update Your System

Begin by updating your existing list of packages. This ensures you have access to the latest versions available in your repositories.

sudo apt update
sudo apt upgrade

Step 2: Install Required Packages

Docker requires a few prerequisite packages to be installed, including support for accessing repositories over HTTPS.

sudo apt install ca-certificates curl gnupg lsb-release

Step 3: Add Docker’s Official GPG Key

Add Docker's GPG key to ensure that the packages you install are authentic and haven’t been tampered with.

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

Step 4: Set Up the Docker Repository

Now that the GPG key is in place, add the official Docker repository to your APT sources list:

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

Step 5: Install Docker Engine

Update your package index with the Docker repository now included, and install Docker Engine and related components:

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

Step 6: Verify Docker Installation

To confirm Docker was installed successfully, run:

docker --version

You can also run the test container provided by Docker:

sudo docker run hello-world

This will download and run a simple container that prints a confirmation message, verifying the engine is functioning correctly.

Step 7: Manage Docker as a Non-root User

By default, you need to prefix Docker commands with sudo. To avoid this and allow your user to run Docker directly:

sudo usermod -aG docker $USER

After running this command, log out and log back in for the group change to take effect. You can confirm your user is now part of the docker group with:

groups

Try running a Docker command without sudo to ensure everything is working:

docker run hello-world

Step 8: Enable and Start Docker on Boot

To make sure Docker runs automatically after reboot, enable the service:

sudo systemctl enable docker
sudo systemctl start docker

Step 9: Uninstall Docker (If Needed)

If at any point you need to remove Docker from your system:

sudo apt purge docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
sudo rm -rf /var/lib/docker
sudo rm -rf /var/lib/containerd

This will completely remove Docker, containers, and all associated data.

Conclusion

You now have a fully functional Docker setup on your Ubuntu server. You can start deploying containers, explore Docker Compose for multi-container apps, or begin learning how to build your own Docker images.