Introduction to roles

Here the Video Transcript

Roles are ways of automatically loading certain vars files, tasks, and handlers based on a known file structure. Grouping content by roles also allows easy sharing of roles with other users. A role can be used in a playbook by adding the tag roles which can be a list of roles:

---
# file: master.yml

- name: Provisioning for the master node
  hosts: master

  roles:
    - ntp_server
...

Once a role is used, it is expected a folder called roles in the same path of the playbook. Inside of the roles directory, Ansible will lookup for a folder with the name of the role used (ntp_server) at execution time. This folder must contain at least one of the following directories:

• tasks - contains the main list of tasks to be executed by the role.

• handlers - contains handlers, which may be used by this role or even anywhere outside this role.

• defaults - default variables for the role (see Working with variables for more information).

• vars - other variables for the role (see Working with variables for more information).

• files - contains files which can be deployed via this role.

• templates - contains templates which can be deployed via this role.

• meta - defines some metadata for this role. See below for more details.

When in use, each directory must contain a main.yml file containing the relevant content. Let us start with a minimal example:

root
├── master.yml
└── roles
    └── ntp_server
        └── tasks
            └── main.yml

The file main.yml in the folder tasks must contain only the list of the tasks; i.e. without the hosts definition or the tasks tag. Extracting the tasks from the NTP server playbook, the main.yml file is:

---
# file: main.yml

- name: Install chrony
  ansible.builtin.yum:
    pkg:
    - chrony
    state: installed

- name: Enable local network devices to access the NTP service
  blockinfile:
    dest: /etc/chrony.conf
    insertafter: '^#allow '
    block: |
      allow 192.168.0.0/20
      allow 192.168.16.0/20

- name: Enable and Restart chronyd daemon
  service:
    name: chronyd
    enabled: true
    state: restarted
 ...

Note that the tasks in the main.yml are not tied to a specific host making the code reusable for any other host.