How to Install Docker on Ubuntu In 7 steps

🚀 How to Install Docker on Ubuntu: A Complete Guide for Developers

How to Install Docker on Ubuntu In 7 steps

Docker has revolutionized how developers build, ship, and run applications. It's an incredibly powerful tool that helps you manage application processes within isolated environments called containers. This guide will walk you through installing Docker on your Ubuntu system, making sure you're ready to dive into the world of containerization! 🐳

Note: This guide is specifically tailored for Ubuntu. The steps might vary slightly for other Linux distributions. We'll be using commands that require sudo, which grants administrative privileges. Always be cautious when using sudo!

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1. Update Your Package List

Before installing anything new, it's a good practice to update your system's package list. This ensures you're getting the latest versions of software and dependencies. Think of it as refreshing your app store before downloading new apps! 🔄

sudo apt update

This command fetches the latest information about available packages from the repositories.

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2. Install Prerequisite Packages

Next, we need to install a few essential packages that allow your system's package manager (apt) to securely download packages over HTTPS. These are like the security keys for your software downloads. 🔑

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

• apt-transport-https: Enables apt to use repositories accessed via the HTTPS protocol.
• ca-certificates: Contains commonly used CA certificates to allow secure connections.
• curl: A command-line tool for transferring data with URLs, used for adding the GPG key.
• software-properties-common: Provides tools for managing software repositories.

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3. Add Docker's GPG Key

To ensure the Docker packages you download are authentic and haven't been tampered with, you need to add Docker's official GPG (GNU Privacy Guard) key to your system. This verifies the integrity of the downloaded packages. ✅

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

• curl -fsSL ...: Downloads the GPG key from Docker's official server.
• sudo apt-key add -: Adds the downloaded GPG key to your system's list of trusted keys.

Heads Up: As of recent Ubuntu versions and security practices, apt-key add is being deprecated. While it still works for now, newer methods involve placing the GPG key directly in /etc/apt/trusted.gpg.d/. For this guide, we'll stick to the common method for simplicity and broader compatibility.

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4. Add the Docker Repository

Now that your system trusts Docker's GPG key, you can add the official Docker repository to your APT sources. This tells your system where to find the Docker packages. 📦

sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable"

• deb [arch=amd64]: Specifies that we are adding a Debian-style repository for AMD64 architecture.
• https://download.docker.com/linux/ubuntu: The URL of the official Docker repository for Ubuntu.
• focal stable: Specifies the Ubuntu release codename (e.g., "focal" for Ubuntu 20.04 LTS) and the "stable" channel for Docker releases. Make sure to replace focal with your Ubuntu version's codename if you're not on 20.04 (e.g., jammy for 22.04, noble for 24.04). You can find your codename by running lsb_release -cs.

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5. Install Docker Engine

With the repository added, it's time to install Docker itself! First, update your package database again to include the newly added Docker packages. Then, we'll verify we're installing from the correct source and finally install Docker CE (Community Edition). 💪

Update Package Database (Again!)

After adding a new repository, it's crucial to update your package list so your system knows about the new Docker packages. ⬇️

sudo apt update

Verify Docker Repository (Optional but Recommended)

Before installing, it's a good idea to confirm that your system is about to install Docker from the official Docker repository and not an older version from Ubuntu's default repositories. This helps prevent unexpected issues. 🤔

apt-cache policy docker-ce

The output should show a high priority for the Docker repository (e.g., https://download.docker.com/linux/ubuntu focal/stable/docker-ce) compared to any other sources.

Install Docker CE

Finally, install the Docker Community Edition package. This will install the Docker Engine, CLI, and containerd. 🎉

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

We're including docker-ce-cli (the command-line interface), containerd.io (the container runtime), and optionally docker-buildx-plugin and docker-compose-plugin which are incredibly useful for building multi-architecture images and managing multi-container Docker applications, respectively.

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6. Verify Docker Installation

After the installation is complete, let's check if Docker is running correctly. This is like turning on a new appliance to make sure it works! ✅

sudo systemctl status docker

The output should indicate that the Docker service is active (running). You'll see something similar to this:

● docker.service - Docker Application Container Engine
     Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
     Active: active (running) since ...
       Docs: https://docs.docker.com
   Main PID: ... (dockerd)
      Tasks: ...
     Memory: ...
        CPU: ...
     CGroup: /system.slice/docker.service
             └─... /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

You can also run a simple test container to verify Docker is working: 🧪

sudo docker run hello-world

This command downloads a test image and runs it in a container. If successful, it will print a message like "Hello from Docker!" and then exit. This confirms Docker can pull images and run containers.

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7. Run Docker Without Sudo (Optional but Highly Recommended)

By default, you need to use sudo every time you run a docker command. This can be tedious and is not always ideal for development workflows. To avoid this, you can add your user to the docker group. This grants your user the necessary permissions to interact with the Docker daemon without needing sudo. 🙌

Add User to Docker Group

Use the following command to add your current user to the docker group:

sudo usermod -aG docker ${USER}

• sudo usermod: Modifies user account information.
• -aG docker: Appends (-a) your user to the docker group (-G docker).
• ${USER}: A shell variable that represents your current username.

Apply Group Changes

For the group changes to take effect, you need to log out and log back in, or you can apply the changes in your current session by typing:

su - ${USER}

This command effectively starts a new shell session with your updated group memberships. You'll be prompted for your password.

Verify Group Membership

To confirm that your user has been successfully added to the docker group, type:

groups

You should see docker listed among your groups. If it is, you're all set to run Docker commands without sudo! 🎉 Try running docker run hello-world again without sudo.

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🎉 Conclusion

Congratulations! You've successfully installed Docker on your Ubuntu system. You're now ready to explore the vast world of containerization, build and run your applications in isolated environments, and streamline your development workflow. Docker is a game-changer, and you've taken the first important step. Happy Dockering! 🚀

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❓ Frequently Asked Questions (FAQs)

Q: What is Docker and why should I use it?

A: Docker is a platform that uses OS-level virtualization to deliver software in packages called containers. Containers are isolated environments that bundle an application and all its dependencies (libraries, frameworks, etc.), ensuring it runs consistently across different environments (development, testing, production). You should use it for consistent environments, easy deployment, scalability, and resource efficiency.

Q: What's the difference between Docker CE and Docker EE?

A: Docker CE (Community Edition) is a free and open-source version of Docker, perfect for developers and small teams. Docker EE (Enterprise Edition) is a subscription-based product with additional features like advanced security, centralized management, and enterprise-grade support, designed for larger organizations.

Q: My `apt-cache policy docker-ce` output doesn't show the Docker repository. What should I do?

A: Double-check step 4 to ensure you correctly added the Docker repository. Make sure there are no typos in the command. Also, confirm you ran sudo apt update after adding the repository.

Q: I'm getting "permission denied" errors even after adding myself to the Docker group.

A: This usually means the group changes haven't taken effect. Remember to either log out and log back in completely, or run su - ${USER} to start a new shell session with the updated group memberships. Simply closing and reopening the terminal might not be enough.

Q: How do I update Docker to a newer version?

A: Since you've added the official Docker repository, you can update Docker just like any other package on your Ubuntu system:

sudo apt update && sudo apt upgrade docker-ce docker-ce-cli containerd.io

This will upgrade Docker to the latest version available in the stable repository.

Q: What if I have an older version of Docker installed?

A: If you have an older version of Docker (like `docker.io` or `docker-engine`) installed from Ubuntu's default repositories, it's recommended to uninstall it first to avoid conflicts. You can usually remove it with:

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