kubespray/roles/kubernetes/preinstall/tasks/0090-etchosts.yml

---
- name: Hosts | populate inventory into hosts file
  blockinfile:
    dest: /etc/hosts
    block: |-
      {% for item in (groups['k8s-cluster'] + groups['etcd'] + groups['calico-rr']|default([]))|unique -%}{{ hostvars[item]['access_ip'] | default(hostvars[item]['ip'] | default(hostvars[item]['ansible_default_ipv4']['address'])) }}{% if (item != hostvars[item]['ansible_hostname']) %} {{ hostvars[item]['ansible_hostname'] }} {{ hostvars[item]['ansible_hostname'] }}.{{ dns_domain }}{% endif %} {{ item }} {{ item }}.{{ dns_domain }}
      {% endfor %}
    state: present
    create: yes
    backup: yes
    unsafe_writes: yes
    marker: "# Ansible inventory hosts {mark}"
  when: populate_inventory_to_hosts_file

- 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 }}"
    state: present
    backup: yes
    unsafe_writes: yes
  when:
    - loadbalancer_apiserver is defined
    - loadbalancer_apiserver.address is defined

- name: Hosts | Retrieve hosts file content
  slurp:
    src: /etc/hosts
  register: etc_hosts_content

- name: Hosts | Extract existing entries for localhost from hosts file
  set_fact:
    etc_hosts_localhosts_dict: >-
       {%- set splitted = (item | regex_replace('[ \t]+', ' ')|regex_replace('#.*$')|trim).split( ' ') -%}
       {{ etc_hosts_localhosts_dict|default({}) | combine({splitted[0]: splitted[1::] }) }}
  with_items: "{{ (etc_hosts_content['content'] | b64decode).split('\n') }}"
  when:
    - etc_hosts_content.content is defined
    - (item|match('^::1 .*') or item|match('^127.0.0.1 .*'))

- name: Hosts | Update target hosts file entries dict with required entries
  set_fact:
    etc_hosts_localhosts_dict_target: >-
      {%- set target_entries = (etc_hosts_localhosts_dict|default({})).get(item.key, []) | difference(item.value.get('unexpected' ,[])) -%}
      {{ etc_hosts_localhosts_dict_target|default({}) | combine({item.key: (target_entries + item.value.expected)|unique}) }}
  with_dict: "{{ etc_hosts_localhost_entries }}"

- name: Hosts | Update (if necessary) hosts file
  lineinfile:
    dest: /etc/hosts
    line: "{{ item.key }} {{ item.value|join(' ') }}"
    regexp: "^{{ item.key }}.*$"
    state: present
    backup: yes
    unsafe_writes: yes
  with_dict: "{{ etc_hosts_localhosts_dict_target }}"