Ansible is one of the most powerful automation tools every DevOps engineer should know. Whether you want to install software on 100+ servers, configure systems, manage deployments, or automate daily tasks — Ansible makes everything super fast and simple.

You now will understand:

• What is Ansible

• Why use Ansible

• Control node & managed nodes

• Inventory file and common fields

• Ad-hoc commands and examples

• Modules and when to use them

What is Ansible? → Why to use it? → Architecture → Installation → Inventory → Ad-Hoc Commands, and finally hands-on examples.

What is Ansible?

Ansible is an open-source automation tool used for:

• Installing packages

• Managing configurations

• Running commands on multiple servers

• Deploying applications

• Orchestrating DevOps pipelines

Think of Ansible as a remote control for your servers. You write instructions → Ansible executes them on all your machines.

Why Ansible?

Here’s why it’s loved in DevOps:

• No agent required (uses SSH)

• Easy to learn (human-readable YAML)

• Works everywhere (cloud, containers, on-prem)

• Scales from small to very large

• Free & open-source

Ansible Architecture (Simple Explanation)

Ansible has only two components:

• Control Node (Master) — The machine where you install Ansible and run commands/playbooks.

• Managed Nodes (Clients) — The servers Ansible controls (via SSH).

Flow: You → Ansible CLI → SSH → Target Server → Action executed

Ansible Setup on Ubuntu (Control Node)

1. nstall Ansible

sudo add-apt-repository ppa:ansible/ansible
sudo apt update -y
sudo apt install ansible -y

2. Setup SSH Key

cd ~/.ssh
vim ansible_key
chmod 700 ~/.ssh
chmod 600 ~/.ssh/ansible_key

Add the same public key to your server’s authorized_keys.

3. Test SSH connection

ssh -i ~/.ssh/ansible_key ubuntu@<server-ip>

# Fix errore if not connect servers
export ANSIBLE_HOST_KEY_CHECKING=False

Inventory File (Very Important)

Default inventory location:

/etc/ansible/hosts

Example hosts file:

[servers]
server1 ansible_host=3.145.29.59
server2 ansible_host=3.150.114.25

[all:vars]
ansible_user=ubuntu
ansible_python_interpreter=/usr/bin/python3
ansible_ssh_private_key_file=/home/ubuntu/.ssh/ansible_key

Inventory fields quick reference

Verify inventory

ansible-inventory --list -i hosts

Test Connection with Ping Module

ansible all -m ping -i hosts

If you see pong, your setup is perfect. 🎉

Ansible Ad-Hoc Commands (Cheat Sheet)

Ad-hoc commands let you run quick commands without playbooks.

Common ad-hoc tasks table

Install Nginx (Examples)

ansible server1 -b -a "apt-get update" 
ansible server1 -b -a "apt-get install nginx -y" 
ansible server1 -b -a "systemctl stop nginx" -i hosts
ansible server1 -b -a "apt-get remove nginx -y" -i hosts

Install Docker (Examples)

ansible server1 -b -a "apt-get update" 
ansible server1 -b -a "apt-get install docker.io -y" 
ansible server1 -b -a "systemctl status docker" -i hosts
ansible server1 -b -a "apt-get remove docker.io -y"

Package Management (Module vs Shell)

Using module (recommended):

ansible all -m apt -a "name=curl,git state=present update_cache=yes" -b

Ad-hoc shell (less ideal):

ansible all -a "apt-get install -y curl git" -b

Quick comparison table: Module vs Ad-hoc shell

Service Management (Module examples)

ansible all -m ansible.builtin.service -a "name=nginx state=started" -b 
ansible all -m ansible.builtin.service -a "name=nginx state=restarted" -b 
ansible all -a "systemctl is-active nginx" -b

File & Log Commands

ansible all -a "du -sh /home/*" -b -i hosts
ansible all -a "tail -n 50 /var/log/syslog" -b

Common Ansible Modules (Handy Table)

Notes & Best Practices

• Always use -b when you need root privileges.

• Prefer modules over raw shell commands.

• Keep inventory organized with groups.

• Test changes on a staging group before production.