update hosts file by Ansible

hosts.j2

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

# variables reflection by setup module
{{nat_ip_address}}    {{ansible_fqdn}} {{ansible_hostname}}

# other IP Mappings

inventory-file

[servers]
127.0.0.1 ansible_connection=local

playbook.yml

- hosts: servers

  vars:
    - nat_ip_address: "{{ansible_all_ipv4_addresses[0]}}"

  tasks:
  - name: generate /etc/hosts
    template: src=hosts.j2 dest=/etc/hosts