Override hosts variable of Ansible playbook from the command line

Question

This is a fragment of a playbook that I\'m using (server.yml):

- name: Determine Remote User
  hosts: web
  gather_facts: false
  roles:
    - {         


        

Answer 1

Here's a cool solution I came up to safely specify hosts via the --limit option. In this example, the play will end if the playbook was executed without any hosts specified via the --limit option.

This was tested on Ansible version 2.7.10

---
- name: Playbook will fail if hosts not specified via --limit option.
  # Hosts must be set via limit. 
  hosts: "{{ play_hosts }}"
  connection: local
  gather_facts: false
  tasks:
  - set_fact:
      inventory_hosts: []
  - set_fact:
      inventory_hosts: "{{inventory_hosts + [item]}}"
    with_items: "{{hostvars.keys()|list}}"

  - meta: end_play
    when: "(play_hosts|length) == (inventory_hosts|length)"

  - debug:
      msg: "About to execute tasks/roles for {{inventory_hostname}}"