How to Install Docker on Ubuntu 22.04

Let's walk through the steps to install Docker on Ubuntu 22.04. This process is straightforward, but there are a few things to keep in mind before we get started.

First, make sure your Ubuntu system is up to date. You can do this by opening a terminal and running:

sudo apt update
sudo apt upgrade -y

Now, let's dive into the installation process.

Step 1: Uninstall Old Versions

Before installing Docker, it's a good idea to remove any old or conflicting Docker packages. This helps avoid potential issues during the installation. Run the following command to remove any existing Docker packages:

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

This command might tell you that some of these packages aren't installed, which is fine. It just means you're starting with a clean slate.

Step 2: Set Up the Docker Repository

To install Docker, we'll use the official Docker repository. This ensures you get the latest stable version of Docker. Here's how to set it up:

1. Install the necessary packages to allow apt to use a repository over HTTPS:

sudo apt-get install ca-certificates curl gnupg lsb-release

2. Add the Docker 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

3. Add the Docker repository to your apt sources:

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 3: Install Docker Engine

Now that the repository is set up, you can install Docker. First, update your package index:

sudo apt-get update

Then, install the latest version of Docker Engine, containerd, and Docker Compose:

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

Step 4: Verify the Installation

To make sure Docker is installed correctly, run the following command:

sudo docker run hello-world

This command downloads a test image and runs it in a container. If everything is set up correctly, you should see a message confirming that Docker is working.

Step 5: Manage Docker as a Non-Root User (Optional)

By default, Docker requires sudo to run commands. If you want to run Docker commands without sudo, you can add your user to the docker group:

sudo usermod -aG docker $USER

After running this command, log out and log back in for the changes to take effect.

Additional Notes

• Firewall Considerations: If you're using a firewall like ufw or firewalld, be aware that Docker can bypass these rules when exposing container ports. Make sure to configure your firewall accordingly.
• Docker and iptables: Docker is only compatible with iptables-nft and iptables-legacy. If you're using nft for firewall rules, you'll need to switch to iptables.
• Upgrading Docker: To upgrade Docker, simply run sudo apt-get update and sudo apt-get upgrade to get the latest version from the repository.

That's it! You've now installed Docker on Ubuntu 22.04. If you run into any issues or need further configuration, refer to the Docker documentation for more detailed instructions.