---
- hosts: localhost
  gather_facts: true
  vars:
    cgroup_search_terms: docker\|lxc\|podman\|oci
    is_container: false
    is_podman: false
    is_docker: false
  tasks:
    - debug: msg="Test if we are in a container!"

    - name: 'Look for container env var defined in /proc/1/environ'
      shell: "grep 'container=' /proc/1/environ"
      register: container_proc_environ
      ignore_errors: true

    - name: 'Look for container info defined in /proc/1/cgroup'
      shell: "grep '{{ cgroup_search_terms}}' /proc/1/cgroup"
      register: container_proc_cgroup
      ignore_errors: true

    - name: 'Found evidence that we are in docker container'
      set_fact:
        is_docker: true
      when: (('container' in ansible_env and ansible_env.container == 'docker') or ansible_virtualization_type == 'docker')

    - name: 'Found evidence that we are in podman container'
      set_fact:
        is_podman: true
      when: ('container' in ansible_env and ansible_env.container == 'podman')

    - name: 'Found evidence that we are in a container'
      set_fact:
        is_container: true
      when: is_docker or is_podman or container_proc_environ.rc == 0 or container_proc_cgroup.rc == 0

    - fail:
      when: not (is_container)