Ansible: Add IPs from inventory to /etc/hosts of all nodes

Solution 1:

The previous answer simply does not work because it adds a new line for the same host instead of modifying the existing line when an IP Address for a host changes.

The following solution takes into account when the ip address changes for a specific server and handles it well by only modifying the line instead of adding duplicate entries.

---
- name: Add IP address of all hosts to all hosts
  lineinfile:
    dest: /etc/hosts
    regexp: '.*{{ item }}$'
    line: "{{ hostvars[item].ansible_host }} {{item}}"
    state: present
  when: hostvars[item].ansible_host is defined
  with_items: "{{ groups.all }}"

Solution 2:

Looks like you have errors in your syntax. Also what version of ansible are you using? The variable names may be different. On version 2.2 this works for me:

- name: Add IP address of all hosts to all hosts
  lineinfile:
    dest: /etc/hosts
    line: "{{ hostvars[item].ansible_host }} {{ hostvars[item].inventory_hostname }} {{ hostvars[item].inventory_hostname_short }}"
    state: present
  with_items: "{{ groups.all }}"

UPDATE

Basil has thought about situations when the IP changes. In that case it is better to use his suggested solution:

- name: Add IP address of all hosts to all hosts
  lineinfile:
    dest: /etc/hosts
    regexp: '.*{{ item }}$'
    line: "{{ hostvars[item].ansible_host }} {{item}}"
    state: present
  when: hostvars[item].ansible_host is defined
  with_items: "{{ groups.all }}"

Solution 3:

I had the same issue and here is my solution for anyone who is interested.

hosts/dev.ini

[controller]
controller1 ansible_ssh_host=10.11.11.10
controller2 ansible_ssh_host=10.11.11.11
controller3 ansible_ssh_host=10.11.11.12

[compute]
compute1 ansible_ssh_host=10.11.11.13
compute2 ansible_ssh_host=10.11.11.14
compute3 ansible_ssh_host=10.11.11.15

[block]
block1 ansible_ssh_host=10.11.11.16
block2 ansible_ssh_host=10.11.11.17

[haproxy]
haproxy1 ansible_ssh_host=10.11.11.18

[nginx]
nginx1 ansible_ssh_host=10.11.11.19

[deployment]
deployment ansible_ssh_host=10.11.11.20

[all:vars]
ansible_python_interpreter=/usr/bin/python3

tasks/main.yml

---
- name: Update /etc/hosts
  become: true
  blockinfile:
      path: /etc/hosts
      create: yes
      block: |
        127.0.0.1 localhost

        # The following lines are desirable for IPv6 capable hosts
        ::1 ip6-localhost ip6-loopback
        fe00::0 ip6-localnet
        ff00::0 ip6-mcastprefix
        ff02::1 ip6-allnodes
        ff02::2 ip6-allrouters
        ff02::3 ip6-allhosts

        {% for item in ansible_play_batch %}
        {{ hostvars[item].ansible_ssh_host }}   {{ item }}    
        {% endfor %}

Notes:

python 3.7.5 ansible 2.9.0
I decided to go with blockinfile instead of using templates because hostvars context was not getting updated inside the template. Plus I was in a hurry :-).