Installing Docker on Debian

Docker is the foundation for almost every application tutorial in the Serverküche. We install it from the official Docker repository – not from the Debian package sources.

What are we building?

By the end, the current Docker Engine with the Compose plugin runs on your Debian 13, installed from the official Docker repository. That has two advantages over the Debian package docker.io: more current versions with timely security updates, and the official docker compose that all Compose recipes here build on.

Prerequisites

• A hardened server with a sudo user

Step by step

Step 1: Set up the repository key

First, install the tools needed to verify the Docker repository:

sudo apt update
sudo apt install -y ca-certificates curl

Then create the keyring directory and download Docker’s GPG key – apt uses it later to check that the packages really come from Docker:

sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/debian/gpg -o /etc/apt/keyrings/docker.asc

Step 2: Add the Docker package source

Add the Docker repository to your package sources. The command detects the architecture and Debian version automatically, so you can copy it unchanged:

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

Step 3: Install Docker

Refresh the package lists (now including the Docker repository) and install the Engine together with the Compose plugin:

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

Check that the service is running:

sudo systemctl status docker

You should see active (running). A quick smoke test:

sudo docker run --rm hello-world

The output Hello from Docker! confirms that the installation works.

Step 4: Use Docker without sudo

Add your user to the docker group so you don’t have to prefix every command with sudo:

sudo usermod -aG docker $USER

After that, docker ps works without sudo and shows a (still empty) container list.

When things go wrong

Maintenance & backups

• Updates: Docker updates along with the normal sudo apt update && sudo apt upgrade – one reason we use the official repository. When the Engine is updated, running containers restart briefly (or stop until you start them again) – plan for that.
• Cleanup: Unused images and build leftovers pile up quickly. docker system df shows the usage, docker system prune cleans up (careful: it also removes stopped containers).
• Backups: The actual data of your applications will later live in volumes or bind mounts – we build the backup strategy for that with encrypted Restic backups and in the individual application tutorials.