- name: set hostname
  hostname:
    name: '{{ hostname_fqdn }}'
  register: hostname

- name: update /etc/hosts
  template:
    src: etc/hosts.j2
    dest: /etc/hosts
  register: hosts_file

- name: gather hostname facts
  setup:
    filter:
      - ansible_fqdn
      - ansible_hostname
      - ansible_domain
  when: hostname.changed or hosts_file.changed