Part 3 – Building a Scalable Ansible Inventory: From Simple Hosts File to group_vars Structure

Managing a handful of servers with Ansible is easy. Managing dozens is still fine. But once you start thinking about hundreds — or even thousands — the traditional hosts file becomes messy, error‑prone, and hard to maintain.

sudo apt install yamllint

yamllint to show something in syntax

yamllint -f colored remove-packages.yml

Add these to variables in vim ~/.vimrc

syntax on
filetype plugin indent on
set autoindent
set smartindent
set nu
set expandtab
set tabstop=2
set shiftwidth=2

initial structure looked like this:

/etc/ansible
├── ansible.cfg
├── hosts
├── playbooks/
└── pyvmomi-community-samples/

And hosts file defined three OS groups

[ubuntu]
gitlab ansible_host=GitLab.ash.local ansible_user=awk ansible_become=yes
[zorin]
platform ansible_host=platform.ash.local ansible_user=awk ansible_become=yes
[centos]
centos01 ansible_host=centos01.ash.local ansible_user=awk ansible_become=yes
centos02 ansible_host=centos02.ash.local ansible_user=awk ansible_become=yes

But as soon as you start adding variables (like package names), the file becomes cluttered and fragile. We can do this but soon it gets messy so we need a new solution to do this than editing the hosts files

centos01 apache_package=httpd
gitlab apache_package=apache2

Move Variables Into group_vars/

Ansible has a built‑in mechanism for this: group_vars/ and host_vars/ for passing variables

Create the directory:

mkdir /etc/ansible/group_vars

Put OS‑specific variables in those files

awk@ansible:/etc/ansible/group_vars$ ls -l
total 12
-rw-r--r-- 1 root root 65 Feb  1 11:02 centos.yml
-rw-r--r-- 1 root root 67 Feb  1 11:02 ubuntu.yml
-rw-r--r-- 1 root root 60 Feb  1 11:02 zorin.yml

for Centos

sudo vi centos.yml

Define OS‑Specific Variables in group_vars for Centos

apache_package: apache2
common_packages:
  - git
  - curl
  - htop

for Ubuntu

sudo vi ubuntu.yml

Define OS‑Specific Variables in group_vars for Ubuntu

apache_package: apache2
common_packages:
  - vlc
  - chrome

for Centos

sudo vi centos.yml

Define OS‑Specific Variables in group_vars for Centos

apache_package: httpd
common_packages:
  - git
  - curl
  - nano

Single OS‑Agnostic Playbook Now Works Everywhere so sreate a playbook:

sudo /etc/ansible/playbooks/install-packages.yml

Use a single OS‑agnostic playbook

- hosts: all
  become: true

  tasks:
    - name: Install Apache based on group variable
      package:
        name: "{{ apache_package }}"
        state: latest

    - name: Install common packages
      package:
        name: "{{ common_packages }}"
        state: latest

Run ansible

ansible-playbook playbooks/install-packages.yml -v

Below are outputs from ansible control node, we are looking at changed value