025 Create a Static Host Inventory File

Tech Tutorial: Install and Configure an Ansible Control Node #

Ansible is a powerful automation tool that simplifies complex configuration management, application deployment, and task automation. It is particularly popular in the system administration, DevOps, and IT automation fields. This tutorial focuses on setting up an Ansible control node on a Red Hat Enterprise Linux (RHEL) system and creating a static host inventory file, which is an essential skill for the Red Hat Certified Engineer (RHCE) exam.

Introduction #

Before diving into the installation and configuration process, it’s important to understand the role of the Ansible control node. The control node is a machine where Ansible is installed and from which all tasks and playbooks are run. It manages the inventory of your hosts, which can be defined in simple text files or dynamically sourced from other systems.

In this tutorial, we will cover:

  1. Installing Ansible on a Red Hat Enterprise Linux system.
  2. Configuring Ansible to manage a group of servers.
  3. Creating and understanding a static host inventory file.

Prerequisites #

  • A Red Hat Enterprise Linux 8 system.
  • Sudo or root access on the machine.
  • Basic familiarity with Linux command line and text editors.

Step-by-Step Guide #

Step 1: Installing Ansible #

First, ensure that your system is registered with Red Hat Subscription Management and that the repositories are enabled. Install Ansible using the following commands:

sudo subscription-manager repos --enable ansible-2.9-for-rhel-8-x86_64-rpms
sudo dnf install ansible

This will install Ansible and its dependencies on your RHEL system.

Step 2: Verify Ansible Installation #

To verify that Ansible has been installed correctly, you can run:

ansible --version

This command will display the Ansible version along with some configuration details.

Step 3: Setting Up the Inventory File #

Ansible uses an inventory file to track all the machines it can communicate with. Here, we’ll create a static inventory file.

  1. Create a directory for your Ansible project:

    mkdir ~/ansible_project
cd ~/ansible_project

  2. Create an inventory file named hosts:

    touch hosts

  3. Open the hosts file with your preferred text editor, for example, vi:

    vi hosts

  4. Add the following content to the hosts file:

    [web]
webserver1.example.com

[db]
dbserver1.example.com

[all:vars]
ansible_user=my_ansible_user
ansible_ssh_private_key_file=/path/to/private/key
    • [web] and [db] are group names that contain the hostnames or IP addresses of your web and database servers, respectively.
    • ansible_user is the common user for all hosts that Ansible will use for SSH connections.
    • ansible_ssh_private_key_file is the path to the SSH private key that Ansible will use for SSH connections.

Step 4: Testing Connectivity #

Test if Ansible can connect to the servers listed in your inventory file by using the ansible command:

ansible all -m ping -i hosts

This command uses the ping module to test SSH connectivity to all hosts in the inventory.

Detailed Code Examples #

Here’s a detailed breakdown of the inventory file:

  • Groups are defined using square brackets []. Any host under [web] will be part of the web group.
  • You can specify variables for groups or individual hosts. In the all:vars section, variables defined are applicable to all hosts.

Conclusion #

In this tutorial, you have learned how to set up an Ansible control node on a RHEL system, configure it, and create a static host inventory file. This setup is fundamental for automating tasks across multiple servers efficiently. With the inventory file, you can group hosts and specify variables that can be used in your playbooks and commands. This knowledge forms a solid foundation for more advanced Ansible topics and prepares you for the RHCE exam.

Remember, practice is key to mastering Ansible, so continue experimenting with different configurations and scenarios to strengthen your skills.