Part 11 – Building a Custom Centos OS for Ansible

Ok, we are now finally at a stage where we can bring together all the ideas into one page.

Add a new host into the ansible host file /etc/ansible/hosts

[centos10]
newvm01 ansible_host=newvm01.ash.local ansible_user=awk ansible_become=yes

Create the automation user awk

sudo useradd -m awk
sudo passwd awk
echo "awk ALL=(ALL) NOPASSWD: ALL" | sudo tee /etc/sudoers.d/awk

Use ssh-copyip to copy the public key

ssh-copy-id awk@newvm01.ash.local

Install ansible on the new vm (managed node)

sudo dnf install -y ansible-core git

The packages to install are in the roles/baseline/vars/main.yml but we can go one step further and create OS‑specific vars files for packages we wish to install and this is what is {{ ansible_distribution }} which picks up the operating system..

roles/baseline/vars/CentOS.yml
roles/baseline/vars/Ubuntu.yml
roles/baseline/vars/Rocky.yml
roles/baseline/vars/Debian.yml

Define the playbook under

/etc/ansible/playbooks/baseline-init.yml 

---
- hosts: all
  become: true
  roles:
    - baseline

This file contains TASKS/VARIABLES that has an existing motd file so we will replace that will jinja.

roles/baseline/templates/motd.j2

Welcome to {{ inventory_hostname }}.
Managed by Ansible Baseline Role.

Environment: {{ motd_environment }}
Owner: {{ motd_owner }}

OS: {{ ansible_distribution }} {{ ansible_distribution_version }}
Kernel: {{ ansible_kernel }}
IP: {{ ansible_default_ipv4.address }}

Here is where the action happen

roles/baseline/tasks/main.yml

The main thing is the include_vars: “{{ ansible_distribution }}.yml” which loads the OS correctly

- name: Load OS-specific variables
  include_vars: "{{ ansible_distribution }}.yml"
  
- name: Baseline role is running
  debug:
    msg: "Baseline tasks executed"

- name: Set system timezone
  timezone:
    name: "Europe/London"

- name: Update package cache
  package:
    update_cache: yes

- name: Upgrade all packages to latest
  package:
    name: "*"
    state: latest

- name: Install baseline packages
  package:
    name: "{{ packages }}"
    state: present

- name: Remove unwanted packages
  package:
    name: "{{ unwanted_packages }}"
    state: absent

- name: Deploy MOTD template
  template:
    src: motd.j2
    dest: /etc/motd
    owner: root
    group: root
    mode: '0644'
  
- name: Ensure SSH service is running
  service:
    name: "{{ ssh_service }}"
    state: started
    enabled: true

Now create the playbook under

playbooks/baseline-init.yml

---
- hosts: all
  become: true
  roles:
    - baseline

Do a dry run just for that group using -l

ansible-playbook playbooks/baseline.yml -l centos10

or, do a dry run just for that host using -l

ansible-playbook playbooks/baseline.yml -l newvm01

Run the playbook

Login and check