Lab 2: Configuration Management with Ansible

Course: Operating Systems 3 (Virtualisation & Cloud Technologies) Week: 11 Topic: Automation and Configuration Management

1. Introduction

In Lab 1, you used Heat and Bash scripts to provision infrastructure. You likely have a stack of servers running (e.g., web-01, web-02). Now, in Lab 2, we will shift gears to Configuration Management.

We will pretend "Day 2" has arrived. Your manager wants you to install the Apache web server on all your instances and ensure a custom index page is deployed. Instead of SSHing into each server manually, you will use Ansible.

Lab Objectives

Install Ansible in a Python virtual environment.
Create a static Inventory file (hosts.yaml).
Execute Ad-Hoc commands to verify connectivity.
Write and Run an Ansible Playbook to configure web servers.

2. Prerequisites

Existing Infrastructure: You should have at least 2 servers running from Lab 1 (or manually created).
Access: You must have the SSH key (mykey.pem) available on your lab machine.
Floating IPs: Ensure you know the Floating IP addresses of your servers.

3. Setup Ansible Environment

Ansible is written in Python. The best way to install it is via pip inside a virtual environment.

Step 1: Create Environment

# Go to your week 11 folder
cd ~/ops3/week11

# Create a virtual environment named 'venv'
python3 -m venv venv

# Activate it
source venv/bin/activate

Step 2: Install Ansible

pip install ansible

Verify installation by running ansible --version.

4. The Inventory

Ansible needs to know which servers to talk to. We will create a file named hosts.yaml.

Step 1: Create hosts.yaml Replace X.X.X.X with the actual Floating IPs of your instances.

all:
  vars:
    ansible_user: ubuntu
    ansible_ssh_private_key_file: mykey.pem
    ansible_ssh_common_args: '-o StrictHostKeyChecking=no'
  children:
    webservers:
      hosts:
        web-01:
          ansible_host: 192.168.100.15  # <--- Replace with your Floating IP
        web-02:
          ansible_host: 192.168.100.16  # <--- Replace with your Floating IP

Edit the file with your real IP addresses.
Ensure mykey.pem is in the same folder.

5. Ad-Hoc Commands

Before writing complex playbooks, verify that Ansible can talk to your servers.

Step 1: The Ping Test The ping module in Ansible doesn't use ICMP; it logs in via SSH and checks if it can run Python.

ansible all -m ping -i hosts.yaml

Success Requirement: You should see a green "ping": "pong" response for each server. If you see "UNREACHABLE," check your IP addresses and SSH key permissions (chmod 600 mykey.pem).

Step 2: Check Uptime Run a raw shell command across the fleet.

ansible webservers -m command -a "uptime" -i hosts.yaml

Verify you get two different uptime responses.

6. Write a Playbook

Now we will automate the installation of Apache. Create a file named install_apache.yaml.

---
- name: Configure Web Fleet
  hosts: webservers
  become: yes  # Equivalent to sudo
  tasks:
    - name: Update apt cache
      apt:
        update_cache: yes

    - name: Install Apache
      apt:
        name: apache2
        state: present

    - name: Create Custom Index Page
      copy:
        content: |
          <html>
          <h1>Configured by Ansible</h1>
          <p>Server: {{ ansible_hostname }}</p>
          </html>
        dest: /var/www/html/index.html

    - name: Ensure Apache is Running
      service:
        name: apache2
        state: started

Understanding the Playbook:

update_cache: Runs apt-get update.
state: present: Installs the package if missing.
copy: key copies text directly into a file on the target.
{{ ansible_hostname }}: A variable that is magically replaced with the real server name.

7. Execution and Verification

Step 1: Run the Playbook

ansible-playbook -i hosts.yaml install_apache.yaml

Step 2: Analyze Output

changed: Ansible made a modification.
ok: The item was already correct (Idempotency).

Step 3: Test Idempotency

Run the exact same command again.
Question: How many tasks show as "changed" this time? (Hint: It should be 0).

Step 4: Verify via Browser Open the Floating IP of web-01 in your browser.

Did you see "Configured by Ansible"?
Did the server name appear correctly?

8. Submission

Submit a short PDF report containing: 1. Screenshot of your ansible all -m ping success. 2. Screenshot of your Playbook run output (The first run vs the second run). 3. Screenshot of the web browser showing the custom page.

Instructor Signature: ___ Date: ___

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