how to create Ansible playbook to obtain OS versions of the remote hosts?

Question

I'm new to ansible. I have a requirement that requires me to pull OS version for of more than 450 linux severs hosted in AWS. AWS does not provide this feature - it rather suggests us to get it from puppet or chef.

I created few simple playbooks which does not run

---
- hosts: testmachine
user: ec2-user
sudo: yes
tasks:
- name: Update all packages to latest
yum: name=* state=latest

task:
- name: obtain OS version
shell: Redhat-release

playbook should output a text file with hostname and OS version. Any insight on this will be highly appreciated.

Answer 1

Use one of the following Jinja2 expressions:

{{ hostvars[inventory_hostname].ansible_distribution }}
{{ hostvars[inventory_hostname].ansible_distribution_major_version }}
{{ hostvars[inventory_hostname].ansible_distribution_version }}

where:

• hostvars and ansible_... are built-in and automatically collected by Ansible
• ansible_distribution is the host being processed by Ansible

For example, assuming you are running the Ansible role test_role against the host host.example.com running a CentOS 7 distribution:

---
- debug:
    msg: "{{ hostvars[inventory_hostname].ansible_distribution }}"
- debug:
    msg: "{{ hostvars[inventory_hostname].ansible_distribution_major_version }}"
- debug:
    msg: "{{ hostvars[inventory_hostname].ansible_distribution_version }}"

will give you:

TASK [test_role : debug] *******************************************************
ok: [host.example.com] => {
    "msg": "CentOS"
}

TASK [test_role : debug] *******************************************************
ok: [host.example.com] => {
    "msg": "7"
}

TASK [test_role : debug] *******************************************************
ok: [host.example.com] => {
    "msg": "7.5.1804"
}

Answer 2

In a structured way:

- hosts: all
  become: no
  vars:
    output_file: os.csv
  tasks:
    - block:
        # For permisison setup.
        - name: get current user
          command: whoami
          register: whoami
          run_once: yes

        - name: clean file
          copy:
            dest: "{{ output_file }}"
            content: 'hostname,distribution,version,release'
            owner: "{{ whoami.stdout }}"
          run_once: yes

        - name: fill os information
          lineinfile:
            path: "{{ output_file }}"
            line: "{{ ansible_hostname }},\
              {{ ansible_distribution }},\
              {{ ansible_distribution_version }},\
              {{ ansible_distribution_release }}"
          # Tries to prevent concurrent writes.
          throttle: 1
      delegate_to: localhost

Creates a comma separated file named os.csv in execution folder. You can use any variables you want editing line:.

Answer 3

Ansible already provides a lot of information about the remote host in the "hostvars" variable that is automatically available.

To see information of your host named "my_remote_box_name", e.g. do

- debug: var=hostvars['my_remote_box_name']

Some OS information is in

hostvars['my_remote_box_name']['ansible_lsb']

Which, for one of my ubuntu hosts would be along:

{
  "hostvars['my_remote_box_name']['ansible_lsb']": {
    "codename": "xenial", 
    "description": "Ubuntu 16.04.1 LTS", 
    "id": "Ubuntu", 
    "major_release": "16", 
    "release": "16.04"
}

You can just use those variables in your playbooks and templates, using the "{{ variable_name }}" notation.

- debug: msg="My release is {{ansible_lsb.release}}"

output:

"msg": "My release is 16.04"