Automating the installation of Docker on Debian with Ansible!

I’m not sure about you, but every time I spin up a new Debian Virtual Machine with Proxmox I find myself getting annoyed with the tedious process of getting Docker and Docker Compose installed.

So in this guide, I will be walking you through my Ansible playbook for installing this amazing software! Automating this task helps reduce the risk of errors and makes it efficient for managing infrastructure.

Prerequisites

This post assumes you have these things set up already:

• A new Debian server with SSH access and/or A hosts file

• Ansible on your local machine

• A playbook for updating apt

If you don’t have a playbook for updating Apt yet then you can follow this guide:

install-docker.yml Playbook

The first playbook installs Docker alone. Let's take a look at it.

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	- hosts: "debian"
	name: Installing Docker
	tasks:
	- name: Check if Docker is installed
	become: yes
	command: docker -v
	register: docker_installed
	ignore_errors: true
	- name: Install Docker
	become: yes
	block:
	- name: Add Docker's official GPG key
	block:
	- name: Update apt
	include_tasks: apt.yml
	- name: Install necessary packages
	become: yes
	ansible.builtin.apt:
	name:
	- ca-certificates
	- curl
	- gnupg
	state: latest
	update_cache: yes
	- name: Add GPG key
	ansible.builtin.shell:
	cmd: |
	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
	- name: Add the repository to Apt sources
	block:
	- name: Add repos
	ansible.builtin.shell:
	cmd: |
	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
	- name: Update apt
	include_tasks: apt.yml
	- name: Install Docker packages
	become: yes
	ansible.builtin.apt:
	name:
	- docker-ce
	- docker-ce-cli
	- containerd.io
	- docker-buildx-plugin
	- docker-compose-plugin
	state: latest
	update_cache: yes
	when: docker_installed.failed
	- name: Ensure Docker group exists
	become: yes
	ansible.builtin.group:
	name: docker
	state: present
	register: docker_group
	- name: Add User to docker group
	become: yes
	ansible.builtin.user:
	name: yourUser
	groups: docker
	append: true
	when: docker_group is changed

view raw install-docker.yml hosted with ❤ by GitHub

I’m sure there are a few Ansible Gurus out there who can figure out ways to optimize this. If there are any, please let me know! I would love to improve.

This playbook assumes there is a hosts section in the host’s file called “debian”. Change this to whatever you need.

- name: Check if Docker is installed
  become: yes
  command: docker -v 
  register: docker_installed
  ignore_errors: true

The first task, “Check if Docker is installed”, will (as the name suggests) check if Docker is first installed. I put that there so there wouldn’t be any issues with machines that already have docker installed. It ignores errors so that way the output won’t say “failed” when the playbook is run.

If the command docker -v fails then the next task will run. You can see the conditional on line 56 ( when: docker_installed.failed ).

I split the second task into multiple, following the official documentation for installing Docker. The child task “Add Docker’s Official GPG key” is also split into a block. It will run the apt.yml playbook from the blog post above and then install some necessary packages.

The “Add GPG key” task could probably be improved, but it simply follows the documentation by running those commands after installing the current packages.

The same is true for “Add the repository to Apt sources”. I just copied the documentation commands and ran them using the Ansible built-in shell and then updated apt again.

- name: Install Docker packages
  become: yes
  ansible.builtin.apt:
    name:
      - docker-ce 
      - docker-ce-cli 
      - containerd.io 
      - docker-buildx-plugin 
      - docker-compose-plugin
     state: latest
     update_cache: yes

Finally “Install Docker packages” will become sudo and install the listed packages using apt.

The last two tasks are only there if you wish to add the user to the Docker group, so you won’t need root privileges every time you want to run a container. I enjoy the convenience so that’s what I do.

    - name: Ensure Docker group exists
      become: yes
      ansible.builtin.group:
        name: docker
        state: present
      register: docker_group

    - name: Add User to docker group
      become: yes
      ansible.builtin.user:
        name: yourUser
        groups: docker 
        append: true 
      when: docker_group is changed

It will first check if the docker group even exists. This is just a failsafe in case the installation didn’t work properly. If it does exist then Ansible will become root again and append yourUser to the docker group. Make sure to change yourUser . If we don’t append the user then it will remove all other groups the user is in and add them only to Docker.

install-docker-compose.yml Playbook

If this is going on a server then you probably want Docker Compose as well. I can probably keep both playbooks inside one, but I find it easier if they are split.

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	- import_playbook: install-docker.yml
	name: Installing Docker
	- hosts: "debian"
	name: Installing docker compose
	tasks:
	- name: Check if Docker Compose is installed
	become: yes
	command: docker-compose -v
	register: docker_compose_installed
	ignore_errors: true
	- name: Install Docker Compose
	become: yes
	block:
	- name: Remove old docker compose package
	ansible.builtin.apt:
	name: docker-compose
	state: absent
	ignore_errors: true
	- name: Get latest Docker Compose version
	uri:
	url: https://api.github.com/repos/docker/compose/releases/latest
	return_content: yes
	register: docker_compose_version
	- name: Extract Docker Compose version number
	set_fact:
	docker_compose_version_number: "{{ docker_compose_version.json.tag_name }}"
	- name: Get Docker Compose based on version number
	become: yes
	ansible.builtin.get_url:
	url: https://github.com/docker/compose/releases/download/{{ docker_compose_version_number }}/docker-compose-Linux-x86_64
	dest: /usr/bin/docker-compose
	mode: '0755'
	when: docker_compose_installed.failed

view raw install-docker-compose.yml hosted with ❤ by GitHub

Before anything, we make sure Docker is first installed by running the playbook we just made. Make sure they are in the same directory otherwise, this would fail.

The first task, like before, checks if Docker Compose is even installed, to begin with by running the docker-compose -v command and checking if the command passes. If it fails then the next block will run.

It will remove an old Docker Compose package as a precaution. Next we “Get the latest Docker Compose version” by calling the GitHub API and registering it as a variable. With the JSON output of the API saved, we can then query it in the next task and extract the version number. If we do it this way then there is no need to hardcode the version number and update the playbook every time a new Docker Compose version is released.

The final task “Get Docker compose based on version number” will get a URL, add it to the desired destination which is the binary folder, and then set privileges for it.

Now it should all be set! To run the playbook use this command:

ansible-playbook path/to/install-docker-comopse.yml -i path/to/hosts