Installing Docker and Docker Compose on Ubuntu 20.04 with Ansible

Prerequisites

Before we begin you’ll need access to a clean installation of Ubuntu 20.04. This tutorial shows you how to install it on VMware Fusion (or VMware Workstation if you’re a Windows or Linux user).

You should also install Ansible on your machine. The steps in this tutorial have been tested on a MacBook Pro with Ansible 2.9.13.

Step 1: Create Inventory

Create the folders to store the Ansible playbook and inventory files.

Let’s call it ansible-docker.

mkdir ~/ansible-docker
mkdir ~/ansible-docker/inventory
touch ~/ansible-docker/inventory/hosts.yml
touch ~/ansible-docker/docker.yml

Open the hosts.yml file and add one or more hosts like shown in the example below.

all:
  hosts:
    gtsrv01:
    gtsrv02:
    gtsrv03:

The IP addresses of the hosts need to be resolvable by DNS or by adding them to your local hosts file. In the example above, I have specified three hosts that Docker will be installed on and made the IP addresses resolvable by adding them to my Macs /etc/hosts file.

Here’s what it looks like:

##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting.  Do not change this entry.
##
127.0.0.1       localhost
255.255.255.255 broadcasthost
::1             localhost

10.1.1.21 gtsrv01
10.1.1.22 gtsrv02
10.1.1.23 gtsrv03

Step 2: Create Docker Playbook

The next thing we need to do is create the Ansible playbook that will be used to install Docker and Docker Compose on the Ubuntu servers. Edit the playbook called docker.yml and add the following contents:

---
- hosts: all
  become: yes
  vars:
    docker_compose_version: "1.27.4"
  tasks:

    - name: Update apt cache
      apt: update_cache=yes cache_valid_time=3600

    - name: Upgrade all apt packages
      apt: upgrade=dist

    - name: Install dependencies
      apt:
        name: "{{ packages }}"
        state: present
        update_cache: yes
      vars:
        packages:
        - apt-transport-https
        - ca-certificates
        - curl
        - software-properties-common
        - gnupg-agent
      
    - name: Add an apt signing key for Docker
      apt_key:
        url: https://download.docker.com/linux/ubuntu/gpg
        state: present

    - name: Add apt repository for stable version
      apt_repository:
        repo: deb [arch=amd64] https://download.docker.com/linux/ubuntu focal stable
        state: present

    - name: Install Docker
      apt:
        name: "{{ packages }}"
        state: present
        update_cache: yes
      vars:
        packages:
        - docker-ce
        - docker-ce-cli 
        - containerd.io

    - name: Add user to docker group
      user:
        name: "{{ansible_user}}"
        group: docker

    - name: Download docker-compose {{ docker_compose_version }}
      get_url:
        url : https://github.com/docker/compose/releases/download/{{ docker_compose_version }}/docker-compose-Linux-x86_64
        dest: ~/docker-compose
        mode: '+x'

    - name: Check docker-compose exists
      stat: path=~/docker-compose
      register: docker_compose

    - name: Move docker-compose to /usr/local/bin/docker-compose
      command: mv ~/docker-compose /usr/local/bin/docker-compose
      when: docker_compose.stat.exists

There is one variable that may need changed called docker_compose_version. It contains the version number of Docker Compose you want to install. As of writing the latest version is 1.27.4.

Step 3: Run Playbook

Run the docker.yml playbook with the following command:

ansible-playbook -i inventory docker.yml -u ubuntu -K 

Note: change the user with the one you use to login to your Ubuntu servers.

You should see Ansible run through each of the steps in the playbook on each of the servers defined in the hosts.yml inventory file.

Now you should be able to SSH onto each host and see that docker has been installed. This can be checked with the following commands:

docker --version
docker-compose --version

Conclusion

This tutorial showed you how to install Docker and Docker Compose on multiple machines by issuing one simple command.

We did this by writing an Ansible playbook that can be committed to a source code repository and shared with the team.

This is faster than manually connecting to each host and running shell scripts. Another benefit is configuration changes are documented when changes are made to the playbook via Git commits.