Pierly: I want to install Docker in a server (Ubuntu 20.04) via Ansible.

Tortoise: There is a playbook to setup that server and it looks as follows:

(setup.yml file)

... other plays ...

- name: Setup load balancers
  hosts: balancers
  become: true
  gather_facts: true
  roles:
    - role: nginx
      tags: nginx
    - role: docker
      tags: docker
  tags:
    - setup

Tortoise: And by the way, the role docker contains, among other tasks, the following one:

(roles/docker/tasks/main.yml file)

... other tasks ...

- name: Add upstream repository
  apt_repository:
    repo: "deb {{ apt_url }} {{ ansible_distribution_release }} stable"

Pierly: Easy task. But, alas, I run ansible-playbook setup.yml --limit balancers --tags docker and it fails with the following message:

The task includes an option with an undefined variable. The error was: 'ansible_distribution_release' is undefined

Tortoise: Damn it! Facts gathering. Not happening. It seems like “it’s a feature not a bug” kind of thing. The topic has been discussed here.

Pierly: Adding the following play at the top of the playbook seems to be good enough:

(roles/docker/tasks/main.yml file)

- hosts: all
  become: true
  gather_facts: true

... other plays ...

Pierly: Everything works as expected because the Facthering part will be implicitly executed every time.

Tortoise: Facthering?

Pierly: For “fact gathering”.

Tortoise: I’m late for a race. Wir sehen uns später.

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