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: Disable and stop chronyd daemon
  service:
    name: chronyd
    enabled: no
    state: stopped
  ignore_errors: true

- name: Install ntpd daemon
  yum:
    name: ntp
    state: latest

- name: Allow IPMI and node network to query ntp server
  blockinfile:
    dest: /etc/ntp.conf
    insertafter: '^#restrict '
    block: |
      restrict 192.168.0.0  mask 255.255.240.0 nomodify notrap
      restrict 192.168.16.0 mask 255.255.240.0 nomodify notrap

- name: Enable and Restart ntpd daemon
  service:
    name: ntpd
    enabled: yes
    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.