Ansible Basic Setup Guide

Introduction & Architecture

Ansible Advantages

• Agentless: No daemons or agents installed on managed nodes (uses SSH).

• Simple: Easy to learn and read using YAML syntax.

• Powerful: Handles complex deployments, configuration management, and orchestration.

• Repeatable: Ensures consistent environments every time you run it.

• Idempotent: Tasks run only when needed (no changes if the state is already correct).

• Extensible: Can be extended using custom modules, plugins, and roles.

Lab Architecture

This diagram shows how the Controller connects to the Agents using SSH.

flowchart LR
    subgraph AWS["AWS Cloud"]

        subgraph Controller["Ansible Controller"]
            A["Ansible Software"]
            Inv["Inventory File"]
            Key["private-key.pem"]
            Cfg["ansible.cfg"]
        end

        Agent1["Agent-01 (Amazon Linux)"]
        Agent2["Agent-02 (Amazon Linux)"]

        Controller -->|SSH Port 22| Agent1
        Controller -->|SSH Port 22| Agent2
    end

Infrastructure Setup (aws)

Step 1: Launch Ec2 Instances

Before installing anything, we need to create the servers on AWS.

1. Launch 3 Instances:

   • OS: Amazon Linux 2 or 2023.

   • Instance Type: t2.micro or t3.micro (Free tier eligible).

   • Key Pair: Create/Select one key pair (e.g., ansible.pem) and download it. Use this same key for all 3 instances.

   • Security Group: Ensure Port 22 (SSH) is open. Allow traffic from your IP and from the Security Group itself (for internal communication).

2. Assign Roles:

   • Instance 1 -> Controller Node (Where we run commands).

   • Instance 2 -> Managed Node 1.

   • Instance 3 -> Managed Node 2.

System Configuration

Step 2: Configure Hostnames

Setting hostnames makes it easier to identify which server you are working on.

A. Configure the Controller Connect to the first instance via SSH and run:

sudo hostnamectl set-hostname ansible-controller

Action: Log out (exit or Ctrl+D) and log back in to see the prompt change to [ec2-user@ansible-controller ~]$.

B. Configure Agent 01 Connect to the second instance:

sudo hostnamectl set-hostname ansible-agent01

C. Configure Agent 02 Connect to the third instance:

sudo hostnamectl set-hostname ansible-agent02

Ansible Installation & Setup

All following steps are performed ONLY on the Ansible Controller Node.

Step 3: Install Ansible

We need to install the Ansible software engine on the controller.

sudo dnf install ansible -y

Step 4: Prepare the Project Directory

It is best practice to keep your Ansible files in a specific folder.

mkdir ~/ansible-project
cd ~/ansible-project

Step 5: Set Up Ssh Key on Controller

Ansible needs the private key (.pem file) to log in to the managed nodes.

1. Upload/Create Key: Copy the content of your ansible.pem (from your local machine) to a new file named your-key.pem inside the ~/ansible-project folder on the controller.

   • You can use nano your-key.pem, paste the content, and save.

2. Secure the Key: SSH requires private keys to have strict permissions (read-only by owner).

   chmod 400 ~/ansible-project/your-key.pem

   Explanation: If you don't do this, SSH will reject the key as "too open".

Connecting Ansible to Nodes

Step 6: Create Inventory File (hosts)

The inventory file tells Ansible which servers to manage and how to connect to them.

Create a file named hosts:

[web]
<node1_public_ip> ansible_user=ec2-user ansible_ssh_private_key_file=~/ansible-project/your-key.pem
<node2_public_ip> ansible_user=ec2-user ansible_ssh_private_key_file=~/ansible-project/your-key.pem

• [web]: This is a group name. You can run commands against all servers in this group.

• <node1_private_ip> public ip for node

• ansible_user: The default user for Amazon Linux is ec2-user.

• ansible_ssh_private_key_file: The path to the key we secured in Step 5.

Step 7: Create Configuration File (ansible.cfg)

This file sets defaults so you don't have to type flags manually every time.

Create a file named ansible.cfg in the same directory:

[defaults]
inventory = ./hosts
host_key_checking = False

• inventory: Tells Ansible to look at the hosts file we just made.

• host_key_checking = False: Prevents the interactive "Are you sure you want to connect?" prompt, which is crucial for automation.

Verification

Step 8: Test Connectivity

Now, let's verify that the Controller can talk to the Agents using the ping module.

ansible web -m ping

Expected Output: You should see a green "SUCCESS" message for both nodes.

172.31.x.x | SUCCESS => {
    "ping": "pong"
}
172.31.y.y | SUCCESS => {
    "ping": "pong"
}

Note: This is not a network ping (ICMP); it verifies that Ansible can SSH into the node, find Python, and execute a script.