How to install docker on RHEL using Ansible role

Introduction

Hi everyone! Today in this blog, we will be installing Docker by creating an Ansible role.

Roles are a feature in Ansible that simplifies the playbook. We can break a complex Ansible playbook into fully independent or interdependent collections of files, tasks, templates, variables, and modules. This enhances reuse-ability and promotes modularisation of configuration. We can create an Ansible role using the following command –

$ ansible-galaxy init <role_name>

Now, let’s follow a step by step approach to create our role to install Docker.

1. Create a directory

$ mkdir ansible && cd ansible

2. Create a role

$ ansible-galaxy init install_docker

The role structure would look like this –

3. Write yaml files

Now, let’s start writing our yaml files one by one. First, change directory to tasks.

$ cd tasks/

Then create a file installPackages.yml which will install all the required packages. Write the following code in it –

- name: Install required packages
  yum:
    name: "{{ item }}"
    state: latest
  with_items:
    - yum-utils
    - device-mapper-persistent-data
    - lvm2

Next, create a file addRepo.yml which will add and enable the official docker repository. Write the following code in this file –

    - name: Add Docker repo
      get_url:
        url: "{{ docker_repo }}"
        dest: /etc/yum.repos.d/docer-ce.repo
        
    - name: Enable Docker Edge & Test repo
      ini_file:
        dest: /etc/yum.repos.d/docer-ce.repo
        section: "{{ item }}"
        option: enabled
        value: 0
      with_items: ['docker-ce-test', 'docker-ce-edge']

Next file into the line is installDocker.yml which will install and start the docker service. It contains the following code –

    - name: Install Docker
      package:
        name: docker-ce
        state: latest

    - name: Start Docker service
      service:
        name: docker
        state: started
        enabled: yes

Lastly, let’s write a file named addUser.yml to add the user. The code is –

- name: Add user vagrant to docker group
  user:
    name: vagrant
    groups: docker
    append: yes

So, now we have 4 yaml files to get our task done. Now, let’s add the following code in the main.yml inside the same directory –

---
# tasks file for install_docker

- import_tasks: installPackages.yml
- import_tasks: addRepo.yml
- import_tasks: installDocker.yml
- import_tasks: addUser.yml

Now, let’s change our directory to vars and put the following code into its main.yml –

---
# vars file for install_docker

docker_repo: "https://download.docker.com/linux/centos/docker-ce.repo"

4. Write the main playbook

We now just have to write a main playbook to use this ansible role. It should be created outside the install_docker role’s directory. Let’s name this docker.yml and write the following code in it –

---
- name: Install docker on RHEL
  hosts: localhost
  become: yes
  roles:
    - install_docker

We’re done writing the code. Now, the code structure should look like this inside the ansible directory –

Finally, let’s run this playbook with the following command –

ansible-playbook docker.yml

If everything has been done correctly, we should see the following output –

I hope this article was informative and useful to you. Please feel free to drop any comment, question, suggestion or improvement.