5.0 - Ansible Roles - Basics

During this lab we’ll learn how to write and use Ansible roles.

Task 1

  • Create a directory roles in your techlab folder.
  • Configure your ansible environment to use the roles folder as an additional resource for roles.

Task 2

Write a role httpd in your new roles folder which does the following:

  • Install httpd, start its service and enable it to run on boot.
  • Install firewalld, start its service and allow traffic for the services http and https.

Task 3

  • Modify your playbook webserver.yml to use your new httpd role. It should be run on all hosts in the web group.
  • Run your playbook and check if everything went as expected.

Task 4

  • Create a new role called base. Its file tasks/main.yml should import the files motd.yml and packages.yml. (Create both files under tasks/).
  • motd.yml should do the following: Use the variable motd_content to change the /etc/motd content to “This is a server\n”. Remember to move the template as well as the variable to a correct location in the roles folder.
  • packages.yml should install the packages firewalld, yum-utils, dos2unix, emacs and vim
  • Write a playbook prod.yml that applies the role base to all servers and the role httpd only to the group web

Task 5

  • Rewrite the httpd role to apply the base role each time it is used in a playbook. Use a dependency in the meta/main.yml file.
  • Remove the play to run base role on all hosts in the prod.yml playbook. Run the playbook and see if role base was applied on hosts in the web group as well.

Solutions

$ mkdir roles
$ grep roles_path ansible.cfg
roles_path    = /etc/ansible/roles:/usr/share/ansible/roles:/home/ansible/techlab/roles

$ cd roles/
$ ansible-galaxy init httpd

$ cat roles/httpd/tasks/main.yml
---
# tasks file for httpd
- name: install packages
  yum:
    name:
      - httpd
      - firewalld
    state: installed
- name: start services
  service:
    name: "{{ item }}"
    state: started
    enabled: yes
  with_items:
    - httpd
    - firewalld
- name: open firewall for http and https
  firewalld:
    service: "{{ item }}"
    state: enabled
    immediate: yes
    permanent: true
  with_items:
    - http
    - https

$ cat webserver.yml
---
- hosts: web
  become: yes
  roles:
    - httpd

$ ansible-playbook webserver.yml

$ cd roles/; ansible-galaxy init base;

$ cat roles/base/defaults/main.yml
---
# defaults file for base
motd_content: "This is a server\n"

$ ls roles/base/tasks/
main.yml      motd.yml      packages.yml

$ cat roles/base/tasks/motd.yml
---
- name: put motd template
  template:
    src: templates/motd.j2
    dest: /etc/motd

$ cat roles/base/tasks/packages.yml
---
- name: install packages
  yum:
    name:
      - firewalld
      - yum-utils
      - dos2unix
      - emacs
      - vim
    state: installed

$ cat roles/base/tasks/main.yml
---
# tasks file for base
- name: set custom text
  include: motd.yml
  tags: motd
- name: install packages
  include: packages.yml
  tags: packages

$ cat prod.yml
---
- hosts: all
  become: yes
  roles:
    - base

- hosts: web
  become: yes
  roles:
    - httpd

Take notice of the different content of /etc/motd on the control node!

$ cat roles/httpd/meta/main.yml
---
dependencies:
  - base
$ cat prod.yml
---
- hosts: web
  become: yes
  roles:
    - httpd

$ ansible-playbook prod.yml