Automate Docker & Docker‑Compose Installation with Ansible – A Step‑by‑Step Guide

Ansible is a Python‑based automation tool that enables cluster management and common operational tasks across dozens to thousands of virtual machines.

In many companies, services are deployed on clusters, and Ansible allows batch operations on one or multiple clusters.

The author works on service automation and has encountered several automation platforms, including:

An Ansible‑script‑driven deployment and upgrade platform.

A Jenkins‑style CI/CD pipeline platform.

A Python‑script‑driven SDK‑based operations platform.

Docker containers with orchestration.

This article shares experience automating the installation of Docker and Docker‑Compose with Ansible.

1. Install Ansible

The control machine must have Python 2; Windows cannot be used as a control host, but Red Hat, Debian, CentOS, macOS, BSD, etc., are supported.

Using pip

<code>sudo pip install ansible</code>

Using system package managers

On CentOS:

<code>sudo yum install ansible</code>

On Ubuntu:

<code>sudo apt-get install software-properties-common
sudo apt-add-repository ppa:ansible/ansible
sudo apt-get update
sudo apt-get install ansible</code>

2. Basic Ansible Usage

Using ansible‑playbook

An

ansible‑playbook

(playbook) combines a series of automation tasks into an ordered, logical workflow.

Typical command to run a playbook:

<code>ansible-playbook docker.yml -i hosts -u alex -k -K</code>

This command specifies the remote user and prompts for the SSH password and sudo password.

To discover module usage, Ansible provides

ansible‑doc

:

<code># List all modules
ansible-doc -l
# Show documentation for the yum module
ansible-doc yum</code>

Playbook Directory Structure

<code>├── group_vars           <- common variables for all hosts
│   └── all
├── hosts                <- inventory file
├── roles                <- reusable roles (e.g., etcd, initial, loop)
│   ├── etcd
│   │   ├── files        <- files to copy to target
│   │   ├── handlers
│   │   ├── tasks
│   │   └── templates
│   ├── initial
│   │   ├── files
│   │   ├── handlers
│   │   ├── tasks
│   │   └── templates
│   └── loop
│       ├── files
│       ├── handlers
│       ├── tasks
│       └── templates
└── site.yml            <- main entry playbook</code>

3. Ansible Playbook to Install Docker

The following playbook automates Docker installation on CentOS, including checks, package installation, adding the user to the Docker group, and installing pip and Docker‑Compose.

Prefer Built‑in Modules

When possible, use Ansible's built‑in modules instead of raw shell commands. For example:

<code># Using a shell command
- name: install yum-utils
  shell: yum install yum-utils

# Using the yum module
- name: install yum-utils
  yum:
    name: yum-utils
    state: present</code>

Similarly, install Docker‑Compose with the

pip

module:

<code>- name: install docker-compose
  pip:
    name: docker-compose
    extra_args: "-i {{ pip.index_url }} --trusted-host {{ pip.trusted_host }}"</code>

Using register and when

The

register

keyword stores a task's result in a variable, and

when

can conditionally run subsequent tasks based on that result. Example:

<code>- name: check docker
  shell: docker -v
  register: result
  ignore_errors: true

- name: include tasks if Docker is missing
  include_tasks: install.yml
  when: result is failed</code>

Execution results (example screenshots):

Source: https://cloud.tencent.com/developer/article/2123531