Docker Setup & Usage Guide

This guide details how to install the Docker Engine on a Debian system. We will use the method recommended by Docker, installing it from Docker's official apt repository to ensure we get the latest and most stable version.

Why Use Docker?

Docker is an open-source containerization platform that allows developers to package applications and all their dependencies (libraries, system tools, code, etc.) into a lightweight, portable container.

• Environment Consistency: Ensures that an application runs the same in development, testing, and production environments.
• Rapid Deployment: Containers start and stop extremely quickly, far surpassing traditional virtual machines.
• Resource Isolation: Containers are isolated from each other, ensuring higher security.
• Powerful Ecosystem: Docker Hub has millions of pre-built images that can significantly speed up the development process.

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Step 1: Set Up Docker's apt Repository

On a fresh system, we first need to perform some setup to allow the system to trust and download software from the official Docker repository.

1.1 Uninstall Old Versions (Optional)

If you have older versions of Docker installed on your system, it's recommended to uninstall them first.

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

1.2 Install Dependencies

Install some necessary packages to allow apt to use a repository over HTTPS.

sudo apt-get update
sudo apt-get install \
    ca-certificates \
    curl \
    gnupg

1.3 Add Docker's Official GPG Key

This ensures that the packages you download are officially signed by Docker and have not been tampered with.

sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/debian/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg

1.4 Set Up the Repository Address

Add the address of the Docker official repository to your apt sources list.

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

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Step 2: Install Docker Engine

Now we can officially install Docker.

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

• docker-ce: Docker Community Edition, the Docker engine itself.
• docker-ce-cli: The Docker command-line tool.
• containerd.io: A container runtime.
• docker-buildx-plugin: Provides support for BuildKit, enhancing build capabilities.
• docker-compose-plugin: Integrates the docker compose command.

After the installation, the Docker service will start automatically.

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Step 3: Verify and Manage the Docker Service

3.1 Verify Installation

Run the classic hello-world image to verify that Docker is installed correctly and can run.

sudo docker run hello-world

If you see a message including "Hello from Docker!", then congratulations, everything is working correctly!

3.2 Manage the Docker Daemon

You can use systemctl to manage the state of the Docker service.

# Check the Docker service status
sudo systemctl status docker

# Stop the Docker service
sudo systemctl stop docker

# Start the Docker service
sudo systemctl start docker

# Enable auto-start on boot (enabled by default)
sudo systemctl enable docker

# Disable auto-start on boot
sudo systemctl disable docker

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Step 4: (Recommended) Manage Docker as a Non-root User

By default, the docker command requires sudo privileges. To avoid typing sudo every time, you can add your current user to the docker group.

4.1 Create the docker group (if it doesn't exist)

It is usually created automatically during installation, but you can check.

sudo groupadd docker

If it says the group already exists, you can ignore it.

4.2 Add Your User to the Group

sudo usermod -aG docker $USER

$USER is an environment variable that will be automatically replaced with your current username.

4.3 Activate the Changes

Important: After running this command, you must log out completely and log back in to the server, or reboot the system, for your group permissions to update.

After logging back in, you can use the docker command directly, for example:

docker ps

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Core Commands

Here are some of the most basic and frequently used Docker commands:

• docker pull <image_name>: Pulls an image from Docker Hub.
• docker images: Lists all locally available images.
• docker run [options] <image_name>: Creates and starts a container from an image.
• docker ps: Lists currently running containers.
• docker ps -a: Lists all containers (including stopped ones).
• docker stop <container_id_or_name>: Stops a running container.
• docker start <container_id_or_name>: Starts a stopped container.
• docker rm <container_id_or_name>: Removes one or more containers.
• docker rmi <image_id_or_name>: Removes one or more images.

You are now ready to start your containerization journey on Debian!