Tech Tutorial: Use Roles and Ansible Content Collections #

Introduction #

In the world of automated configuration and deployment, Ansible stands out for its simplicity and versatility. For Red Hat Certified Engineer (RHCE) candidates, understanding how to effectively utilize Ansible is crucial. This tutorial will delve into creating and working with roles and leveraging Ansible Content Collections, focusing specifically on Red Hat Enterprise Linux (RHEL).

Roles in Ansible are units of organization that allow for reusable content, making playbook development and maintenance easier. Ansible Content Collections, on the other hand, are a format for packaging and distributing Ansible content, including roles, plugins, and modules.

Step-by-Step Guide #

Setup Ansible on RHEL #

Before diving into roles and collections, ensure Ansible is installed on your RHEL system. You can install Ansible through the Red Hat Subscription Management (RHSM):

sudo subscription-manager repos --enable ansible-2-for-rhel-8-x86_64-rpms
sudo dnf install ansible

Creating a Role #

Roles organize tasks, handlers, files, templates, and variables into a structured directory. We will create a role to configure a web server.

1. Create Role Directory Structure

   Use the ansible-galaxy command to initialize a new role:

   ansible-galaxy init web_server
   

   This command creates a directory structure under web_server:

   web_server/
   ├── defaults
   │   └── main.yml
   ├── files
   ├── handlers
   │   └── main.yml
   ├── meta
   │   └── main.yml
   ├── README.md
   ├── tasks
   │   └── main.yml
   ├── templates
   ├── tests
   │   ├── inventory
   │   └── test.yml
   └── vars
       └── main.yml
   

2. Add Tasks

   Edit web_server/tasks/main.yml to install and start Apache:

   ---
   - name: Install httpd
     yum:
       name: httpd
       state: present
   
   - name: Start httpd service
     systemd:
       name: httpd
       state: started
       enabled: yes
   

Using the Role in a Playbook #

Create a playbook deploy_web.yml that uses the web_server role:

---
- hosts: all
  become: yes

  roles:
    - web_server

Ansible Content Collections #

Ansible Collections allow you to organize, share, and use roles across different projects.

1. Creating a Collection

   Initialize a new collection using ansible-galaxy:

   ansible-galaxy collection init my_namespace.my_collection
   

   This command generates a collection structure:

   my_collection/
   ├── docs/
   ├── galaxy.yml
   ├── plugins/
   │   └── modules/
   ├── README.md
   ├── roles/
   └── tests/
   

2. Add Role to Collection

   Move or link the web_server role into my_collection/roles/.

3. Using Collection in a Playbook

   Update deploy_web.yml to use the role from the collection:

   ---
   - hosts: all
     become: yes
   
     collections:
       - my_namespace.my_collection
   
     roles:
       - web_server
   

Detailed Code Examples #

Here’s a more complex task included in the web_server role to configure virtual hosts:

- name: Configure virtual hosts
  template:
    src: vhosts.j2
    dest: /etc/httpd/conf.d/{{ item.vhost_name }}.conf
  loop:
    - { vhost_name: 'site1', server_admin: 'webmaster@site1.com', document_root: '/var/www/site1' }
    - { vhost_name: 'site2', server_admin: 'webmaster@site2.com', document_root: '/var/www/site2' }
  notify: restart httpd

This task uses the template module to create virtual host configurations from a Jinja2 template, iterating over a list of virtual hosts.

Conclusion #

Understanding and utilizing roles and collections in Ansible can significantly streamline the process of managing complex deployments across various environments. By encapsulating configuration logic into roles and organizing roles into collections, you can reuse code efficiently and maintain cleaner, more manageable playbooks. This tutorial has shown you how to establish these components in a RHEL environment, providing a strong foundation for further exploration and proficiency in Ansible automation.