019 Use Provided Documentation to Look Up Specific Information About Ansible Modules and Commands

Tech Tutorial: Understand Core Components of Ansible #

Introduction #

Ansible is a powerful automation tool that simplifies configuration management, application deployment, and task automation. It uses a straightforward YAML syntax and connects over SSH without requiring agent installation on the remote systems. This tutorial aims to help you use Ansible’s documentation effectively to find information about its modules and commands, focusing specifically on the context of Red Hat Enterprise Linux (RHEL), in preparation for the Red Hat Certified Engineer (RHCE) exam.

Step-by-Step Guide #

1. Accessing Ansible Documentation #

Before diving into specific commands and modules, it’s crucial to understand how to access and use the Ansible documentation. Ansible documentation can be accessed in several ways:

Online Documentation #

The most comprehensive resource is the official Ansible documentation site. This site includes user guides, installation guides, and detailed descriptions of all modules and plugins.

Command Line Access #

On a RHEL system, after installing Ansible, you can also access documentation from the command line using the ansible-doc command. For example, to see information about the yum module, you would run:

ansible-doc yum

This command displays usage, parameters, examples, and much more about the yum module directly in your terminal.

2. Understanding Core Components #

Ansible’s core components include modules, tasks, plays, playbooks, facts, variables, and inventories. Below, we’ll explore how to find information about these components using the ansible-doc command.

Modules #

Modules are the units of work in Ansible. Each module has a specific purpose, such as managing packages with the yum module or controlling services with the systemd module. To find more about a specific module, use ansible-doc followed by the module name. Here’s how to look up the firewalld module, which is pertinent to managing firewall rules in RHEL:

ansible-doc firewalld

Playbooks #

Playbooks are the files where Ansible code is written, usually in YAML format. Although ansible-doc doesn’t provide direct documentation on playbook writing, it can be useful for finding module-specific usage that can be written into playbooks.

3. Detailed Code Examples #

Let’s create a simple playbook that updates all packages on a RHEL system using the yum module and then ensures that the httpd service is running using the systemd module.

---
- name: Update all packages and start httpd
  hosts: all
  become: yes

  tasks:
    - name: Ensure all packages are up to date
      yum:
        name: "*"
        state: latest

    - name: Ensure the httpd service is running
      systemd:
        name: httpd
        state: started
        enabled: yes

In this example:

  • hosts: all specifies that the playbook runs on all inventory hosts.
  • become: yes escalates privileges.
  • The yum task updates all packages.
  • The systemd task ensures httpd is running and enabled on boot.

4. Using ansible-doc to Explore More Examples #

For more real-world examples, use the -s flag with ansible-doc to show playbook snippets. For instance:

ansible-doc -s yum

This command will show you how to use the yum module within a playbook context.

Conclusion #

Understanding how to navigate and utilize the Ansible documentation is crucial for effective automation with Ansible, especially in professional environments like those managed under RHEL policies. This tutorial has introduced how to access module and command documentation with ansible-doc, and provided a simple playbook example. As you prepare for the RHCE exam, make frequent use of ansible-doc to familiarize yourself with the modules and options available in Ansible, ensuring you’re well-prepared for practical automation challenges.