[ansible@control rhce8-book]$ cat listing79.yaml
---
- name: check for existence of devices
  hosts: all
  tasks:
  - name: check if primary disk exists
    debug:
      msg: a primary disk exists
    when: ansible_facts['devices']['sda'] is defined or ansible_facts['devices']['nvme0n1'] is defined
  - name: check if econdary disk exists
    debug:
      msg: a secondary disk exists
    when: ansible_facts['devices']['sdb'] is defined or ansible_facts['devices']['nvme0n2'] is defined
  - name: dummy test, intended to fail
    debug:
      msg: failing
    when: dummy is defined
  - name: check if /dev/sdc does not exist
    debug:
      msg: there is no /dev/sdc device
    when: ansible_facts['devices']['sdc'] is not defined