Mastering Ansible: A Step-by-Step Tutorial

8 September 2023

We’ll be diving straight into the core concepts and components that will help you become proficient in Ansible. This tutorial assumes that you have already installed Ansible on your system and have a basic understanding of what Ansible is.

Setting Up the Environment#

SSH Key Generation#

If you haven’t already, generate an SSH key pair on your Ansible control node.

ssh-keygen -t rsa

SSH Key Distribution#

Copy the SSH public key to all your target nodes.

ssh-copy-id username@target_host

Replace username with the appropriate user and target_host with the IP address or hostname of the target node.

Inventory Files#

Simple Inventory#

Create a simple inventory file with the .ini extension.

# my_inventory.ini
[web]
192.168.1.2

[db]
192.168.1.3

Dynamic Inventory#

You can also use dynamic inventory scripts. Ansible supports scripts that output JSON.

#!/usr/bin/python
import json
inventory = {
  "web": ["192.168.1.2"],
  "db": ["192.168.1.3"]
}
print(json.dumps(inventory))

Ad-hoc Commands#

Execute commands directly on your nodes.

ansible web -i my_inventory.ini -m ping

This will run the ping module on all nodes under the [web] group in my_inventory.ini.

Writing Playbooks#

Your First Playbook#

Create a YAML file named my_first_playbook.yml.

---
- name: My First Playbook
  hosts: web
  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present

Run the playbook with the ansible-playbook command.

ansible-playbook -i my_inventory.ini my_first_playbook.yml

Multi-Task Playbook#

You can have multiple tasks in a playbook.

---
- name: Web Server Setup
  hosts: web
  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present
    - name: Start Nginx Service
      service:
        name: nginx
        state: started

Roles and Role-based Playbooks#

Roles allow you to organize your playbooks into reusable components.

ansible-galaxy init web-server

This will generate a web-server role directory with various subdirectories (tasks, vars, templates, etc.).

Using Roles in Playbook#

---
- name: Web Server Role-based Playbook
  hosts: web
  roles:
    - web-server

Role Variables#

In web-server/vars/main.yml, define some variables.

http_port: 80
https_port: 443

In web-server/tasks/main.yml, use those variables.

---
- name: Configure Nginx
  template:
    src: nginx.conf.j2
    dest: /etc/nginx/nginx.conf
  vars:
    http_port: "{{ http_port }}"
    https_port: "{{ https_port }}"

Variables and Facts#

Playbook Variables#

Define variables in your playbooks.

---
- name: Variable Example
  hosts: web
  vars:
    my_variable: "Hello, World!"

Gathering Facts#

Ansible can gather facts (system information) about target nodes.

---
- name: Gather Facts
  hosts: all
  tasks:
    - setup:

Conditionals and Loops#

Conditionals#

Execute tasks conditionally.

---
- name: Conditional Playbook
  hosts: all
  tasks:
    - name: Install Apache if system is Ubuntu
      apt:
        name: apache2
        state: present
      when: ansible_facts['os_family'] == "Debian"

Loops#

Execute tasks in a loop.

---
- name: Loop Example
  hosts: all
  tasks:
    - name: Install multiple packages
      apt:
        name: "{{ item }}"
        state: present
      loop:
        - git
        - vim
        - curl

Templates and Files#

Template Basics#

Ansible uses Jinja2 for templating. Create a template file with the .j2 extension.

# my_template.j2
Hello, {{ my_variable }}!

Using Templates in Tasks#

---
- name: Template Example
  hosts: web
  tasks:
    - name: Deploy template
      template:
        src: my_template.j2
        dest: /tmp/my_template.txt
  vars:
    my_variable: "World"

Advanced Concepts#

Tags#

Use tags to selectively run specific tasks.

---
- name: Tag Example
  hosts: all
  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present
      tags: ["web"]

Run only the tagged tasks.

ansible-playbook -i my_inventory.ini my_playbook.yml --tags "web"

Error Handling#

Add error handling to your playbooks.

---
- name: Error Handling Example
  hosts: all
  tasks:
    - name: Attempt to install package
      apt:
        name: some-nonexistent-package
        state: present
      ignore_errors: true

Troubleshooting and Debugging#

Verbose Output#

Run Ansible commands with -vvv for verbose output.

ansible-playbook -i my_inventory.ini my_playbook.yml -vvv

Debug Module#

Use the debug module to print variables.

---
- name: Debug Example
  hosts: all
  tasks:
    - debug:
        var: my_variable

And that concludes our in-depth tutorial on mastering Ansible. Hopefully, this guide has helped you navigate through the various components and intricacies of Ansible, enabling you to manage and automate your infrastructure with ease.