How to create host file with ansible with play hosts IP

Question

I am trying to create a hosts file with following task. I am running this task on machines completely out of groups['hadoop']. Here I want to create hosts file for nodes from groups['hadoop'] without running my this play on groups['hadoop']

- name: Update /etc/hosts
  lineinfile: dest=/etc/hosts
          regexp='.*{{ item }}$'
          line="{{ hostvars[item].ansible_default_ipv4.address }} {{item}}"
          state=present
  when: hostvars[item].ansible_default_ipv4.address is defined
  with_items: groups['hadoop']
  tags:
    - etc-hosts

I tried this but it didn't work, it worked only when I have groups['hadoop'] in my play hosts.

Anyone know what I am doing wrong here ?

udondan · Accepted Answer · 2016-03-14 17:11:40Z

1

Ansible will detect facts like the IP through the setup module. This is by default executed as very first task of a play on those hosts which will be processed by the play. Therefore Ansible only knows facts about the hosts of the current play. Not part of the play -> no details available.

To solve this you have two options.

1) Add a play without tasks, just to run the setup module on the hadoop hosts.

---

 - hosts: hadoop
   gather_facts: yes

 - hosts: other hosts
   tasks: your actual tasks here

...

2) Enable fact caching. Fact caching, as the name suggests, provides a way for Ansible to memorize facts about hosts it did not process in the current playbook. For this you will need to set up a redis instance locally or somewhere available on the network.

answered Mar 14, 2016 at 17:11

udondan

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