cleanup-hosts/tasks/main.yml

---
- name: Detect domain name
  set_fact:
    domainname: "{{ ansible_dns.domain|default(False) or ansible_dns.search.0|default(False) or ansible_domain|default(False) or 'invalid'}}"

- name: Add name/IP to hosts file
  lineinfile:
    dest: /etc/hosts
    regexp: '^{{ ansible_default_ipv4.address }}'
    line: '{{ ansible_default_ipv4.address }} {{ ansible_hostname }}.{{ domainname }} {{ ansible_hostname }}'
    backup: yes

- name: Clean/remove 127.0.1.1
  lineinfile:
    dest: /etc/hosts
    regexp: '^127.0.1.1'
    state: absent
    backup: yes

- name: Ensure 127.0.0.1 localhost
  lineinfile:
    dest: /etc/hosts
    regexp: '127.0.0.1'
    line: '127.0.0.1 localhost localhost.localdomain'
    insertbefore: BOF
    backup: yes