How to Install Docker on Ubuntu: A Step-by-Step Guide for Beginners

Containerization has completely revolutionized how developers build, ship, and run applications. Among the various tools available today, Docker stands out as the undisputed industry standard. By packaging an application and its dependencies into a single lightweight container, Docker ensures that your software runs seamlessly, regardless of the underlying infrastructure.

If you are developing on Linux, Ubuntu is one of the most popular and stable platforms for running containerized workloads. Whether you are setting up a local development environment or preparing a production-ready cloud server, getting Docker up and running on Ubuntu is a fundamental skill every developer should master.

In this comprehensive guide, we will walk you through the step-by-step process of installing Docker Engine on Ubuntu, configuring it for optimal usage, and verifying your installation with a test container.

Step 1: Preparing Your Ubuntu System

Before installing any new software, it is always a best practice to update your local package index to ensure you are working with the latest repository information. Open your terminal and run the following commands to update your system's package list and upgrade existing packages:

sudo apt update
sudo apt upgrade -y

Next, you need to install a few prerequisite packages that allow apt to use packages over HTTPS. These tools are essential for securely downloading and adding Docker's official GPG key:

sudo apt install apt-transport-https ca-certificates curl software-properties-common gnupg -y

With your system updated and prerequisites installed, you are now ready to move on to adding Docker's official repositories.

Step 2: Adding the Official Docker Repository

While Ubuntu’s default repositories sometimes contain older versions of Docker, it is always recommended to install the official Docker Engine to get the latest features, performance improvements, and security patches.

First, add Docker’s official GPG key to ensure the authenticity of the software you are downloading:

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

Next, set up the stable Docker repository by running the following command. This command dynamically detects your Ubuntu version codename (such as jammy or focal) and configures the repository accordingly:

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

Now that the repository has been successfully added, update your local package index once more so apt recognizes the new Docker packages:

sudo apt update

Step 3: Installing Docker Engine

With the repository configured, you are ready to install Docker Engine along with the Docker CLI and container runtime components. Run the following command in your terminal:

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

This command installs several crucial components:

• docker-ce: The Docker Community Edition daemon (the core engine).
• docker-ce-cli: The command-line interface used to interact with Docker.
• containerd.io: The container runtime that manages the complete lifecycle of containers.
• docker-buildx-plugin: Extends Docker with advanced multi-architecture build capabilities.
• docker-compose-plugin: The latest version of Docker Compose, allowing you to run multi-container applications easily.

Once the installation finishes, the Docker service should start automatically. You can verify that the Docker daemon is active and running by typing:

sudo systemctl status docker

Step 4: Executing Docker Without Sudo (Optional but Recommended)

By default, running the docker command requires root privileges, meaning you must prefix your commands with sudo. If you prefer to run Docker commands as a standard user without typing sudo every time, you can add your user account to the docker security group.

Create the docker group if it does not already exist and add your current user to it:

sudo usermod -aG docker $USER

To apply these new group memberships, log out of your system and log back in, or run the following command to refresh your current terminal session immediately:

newgrp docker

Step 5: Verifying the Installation

Now comes the exciting part: testing whether your Docker installation works correctly! Docker provides a lightweight hello-world image specifically designed for this purpose.

Run the following command to download and execute the test container:

docker run hello-world

If your installation was successful, Docker will download the hello-world image, create a container, run it, and print an informational message confirming that the installation is working correctly. This verifies that both the daemon and CLI are communicating properly.

Conclusion

Congratulations! You have successfully installed Docker Engine and Docker Compose on your Ubuntu system. You are now fully equipped to build, test, and deploy containerized applications with confidence.

Containerization simplifies dependency management, scales effortlessly, and ensures consistency across different development and production environments. As you continue your Docker journey, consider exploring advanced topics such as writing multi-stage Dockerfiles, orchestrating containers with Kubernetes, or managing persistent volumes for your databases.