Ansible command line booleans

playbook-book.yml

---
- hosts: all
  vars:
    docker: 0
  tasks:
  - name: ensure bool variables work
    debug: msg="docker {{ docker }}.."
    # When: takes a jinja2 expression
    # 0 evaluates to false
    # >= 1 evaluates to true
    # override the default value with
    #   $ ansible-playbook playbook-bool.yml -e docker=1 ...
    when: docker

  - name: ensure variables can be negated
    debug: msg="not docker!"
    when: not docker

  - debug: msg="not not docker!"
    when: not not docker