7. Creating a Custom Module | Learning Ansible 2

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Table Of Contents

Learning Ansible 2 - Second Edition

By : Fabio Alessandro Locati

2 (1)

Learning Ansible 2

2 (1)

By: Fabio Alessandro Locati

Overview of this book

Ansible is an open source automation platform that assists organizations with tasks such as configuration management, application deployment, orchestration, and task automation. With Ansible, even complex tasks can be handled easier than before. In this book, you will learn about the fundamentals and practical aspects of Ansible 2 by diving deeply into topics such as installation (Linux, BSD, and Windows Support), playbooks, modules, various testing strategies, provisioning, deployment, and orchestration. In this book, you will get accustomed with the new features of Ansible 2 such as cleaner architecture, task blocks, playbook parsing, new execution strategy plugins, and modules. You will also learn how to integrate Ansible with cloud platforms such as AWS. The book ends with the enterprise versions of Ansible, Ansible Tower and Ansible Galaxy, where you will learn to interact Ansible with different OSes to speed up your work to previously unseen levels By the end of the book, you’ll able to leverage the Ansible parameters to create expeditious tasks for your organization by implementing the Ansible 2 techniques and paradigms.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Getting Started with Ansible

1. Getting Started with Ansible

IT automation

What is Ansible?

Secure Shell (SSH)

Why Ansible?

Installing Ansible

Creating a test environment with QEMU and KVM

Version control system

Using Ansible with Git

Summary

2. Automating Simple Tasks

2. Automating Simple Tasks

YAML

Hello Ansible

Working with playbooks

Ansible verbosity

Variables in playbooks

Creating the Ansible user

Configuring a basic server

Installing and configuring a web server

Publishing a website

Jinja2 templates

Summary

3. Scaling to Multiple Hosts

3. Scaling to Multiple Hosts

Working with inventory files

Working with variables

Working with dynamic inventory

Working with iterates in Ansible

Summary

4. Handling Complex Deployment

4. Handling Complex Deployment

Working with the local_action feature

Delegating a task

Working with conditionals

Working with include

Working with handlers

Working with roles

Execution strategies

Tasks blocks

The Ansible template - Jinja filters

Security management

Summary

5. Going Cloud

5. Going Cloud

Provisioning resources in the cloud

Amazon Web Service

DigitalOcean

Summary

6. Getting Notifications from Ansible

6. Getting Notifications from Ansible

E-mails

XMPP

Slack

Rocket Chat

Internet Relay Chat (IRC)

Amazon Simple Notification Service

Nagios

Summary

7. Creating a Custom Module

7. Creating a Custom Module

Using Python modules

Using bash modules

Using Ruby modules

Testing modules

Summary

8. Debugging and Error Handling

8. Debugging and Error Handling

The check mode

Indicating differences between files using --diff

Functional testing in Ansible

Functional testing using assert

Testing with tags

The --skip-tags

Managing exceptions

Trigger failure

Summary

9. Complex Environments

9. Complex Environments

Code based on the Git branch

A single stable branch with multiple folders

Software distribution strategy

Preparing the environment

Deploying a web app with revision control systems

Deploying a web app with RPM packages

Building compiled software with RPM packaging

Deployment strategies

Optimizations

Summary

10. Introducing Ansible for Enterprises

10. Introducing Ansible for Enterprises

Ansible on Windows

Ansible for networking devices

Ansible Galaxy

Ansible Tower

Summary

Using Python modules

Ansible intends to allow users to write modules in any language. Writing the module in Python, however, has its own advantages. You can take advantage of Ansible's libraries to shorten your code, an advantage not available for modules in other languages. Parsing user arguments, handling errors, and returning the required values becomes easier with the help of the Ansible libraries. We will see two examples for a custom Python module, one with and one without using the Ansible library, to give you a glimpse of how custom modules work. Make sure you organize your directory structure as mentioned in the previous section before creating the module. The first example creates a module named check_user. To do so, we will need to create the check_user file in the library folder within the Ansible top-level directory, with the following content:

    #!/usr/bin/env python 
 
    import pwd 
    import sys 
    import shlex 
    import json 
 
    def main(): 
        # Parsing...

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