As we are targeting two different operating systems, our tasks/main.yml file needs to look as follows:

---
# tasks file for ansible-role-docker

- name: include the operating system specific variables
  include_vars: "{{ ansible_os_family }}.yml"

- name: install the stack on centos
  import_tasks: install-redhat.yml
  when: ansible_os_family == 'RedHat'

- name: install the stack on ubuntu
  import_tasks: install-ubuntu.yml
  when: ansible_os_family == 'Debian'

As you can see, this is the same as when we installed our LEMP Stack on the two operating systems in Chapter 6, Targeting Multiple Distributions. The tasks/install-redhat.yml file looks pretty much like the tasks we have used to install Docker in the previous chapters:

---
# tasks file for ansible-role-docker

- name: add the gpg key for the docker repo
  rpm_key:
    key: "{{ docker.gpg_key }}"
    state: "present"

- name: add docker repo from the remote url
  get_url:
    url: "{{ docker.repo_url }}"
    dest: "{{ docker.repo_path }}"
    mode: "0644"

- name: install the docker packages
  yum:
    name: "{{ item }}"
    state: "installed"
    update_cache: "yes"
    enablerepo: "{{ docker.edge }}"
  with_items: "{{ docker.packages }}"

- name: install pip
  easy_install:
    name: pip
    state: latest

- name: install the python packages
  pip:
    name: "{{ item }}"
  with_items: "{{ docker.pip }}"

- name: put selinux into permissive mode
  selinux:
    policy: targeted
    state: permissive

- name: start docker and configure to start on boot
  service:
    name: "docker"
    state: "started"
    enabled: "yes"

The only difference is that we are enabling the Docker CE Edge repository when installing the packages, and also we are not running a yum update when installing Docker. We are not doing this as it is not our role's decision to update a server when someone else is running the role; our role should only install Docker.

The final task file is tasks/install-ubuntu.yml. This, as you will have already guessed, contains the tasks to install Docker on Ubuntu hosts:

---
# tasks file for ansible-role-docker

- name: install the system packages
  apt:
    name: "{{ item }}"
    state: "present"
    update_cache: "yes"
  with_items: "{{ docker.system_packages }}"

- name: add the apt keys from a key server
  apt_key:
    url: "{{ docker.gpg_key }}"
    state: present

- name: add the apt repo
  apt_repository:
    repo: "{{ docker.repo }}"
    state: present

- name: install the docker package
  apt:
    name: "{{ item }}"
    state: "present"
    update_cache: "yes"
    force: "yes"
  with_items: "{{ docker.packages }}"

- name: install the python packages
  pip:
    name: "{{ item }}"
  with_items: "{{ docker.pip }}"

- name: start docker and configure to start on boot
  service:
    name: "docker"
    state: "started"
    enabled: "yes"

That concludes all of the tasks and variables that we need in order to install Docker on the two different operating systems. In previous chapters, that would have been enough for us to add the role to our playbook and run the tasks. However, as we are going to be publishing this role on Ansible Galaxy, we need to add some more information about the role.