kubespray/roles/kubernetes/preinstall/tasks/etchosts.yml

---
- name: Hosts | populate inventory into hosts file
  lineinfile:
    dest: /etc/hosts
    regexp: "^{{ hostvars[item]['ip'] | default(hostvars[item].ansible_default_ipv4.address) }} {{ item }}$"
    line: "{{ hostvars[item]['ip'] | default(hostvars[item].ansible_default_ipv4.address) }} {{ item }}"
    state: present
    backup: yes
  when: hostvars[item].ansible_default_ipv4.address is defined
  with_items: groups['all']

- name: Hosts | populate kubernetes loadbalancer address into hosts file
  lineinfile:
    dest: /etc/hosts
    regexp: ".*{{ apiserver_loadbalancer_domain_name }}$"
    line: "{{ loadbalancer_apiserver.address }} {{ apiserver_loadbalancer_domain_name| default('lb-apiserver.kubernetes.local') }}"
    state: present
    backup: yes
  when: loadbalancer_apiserver is defined and apiserver_loadbalancer_domain_name is defined

- name: Hosts | localhost ipv4 in hosts file
  lineinfile:
    dest: /etc/hosts
    line: "127.0.0.1 localhost localhost.localdomain"
    regexp: '^127.0.0.1.*$'
    state: present
    backup: yes

- name: Hosts | localhost ipv6 in hosts file
  lineinfile:
    dest: /etc/hosts
    line: "::1 localhost6 localhost6.localdomain"
    regexp: '^::1.*$'
    state: present
    backup: yes