Julio Dutra

Ansible is a powerful open-source automation tool used for configuration management, application deployment, and task automation. It allows IT administrators and DevOps engineers to manage multiple servers with ease by writing simple, human-readable playbooks in YAML format. This article will guide you through the installation and configuration of Ansible, provide a few usage examples, and demonstrate how to use hosts files to manage your infrastructure.

1. Installing Ansible

1.1. Installation on Ubuntu/Debian

To install Ansible on an Ubuntu or Debian-based system, follow these steps:

1. Update the package repository:

sudo apt update

1. Install Ansible:

sudo apt install ansible -y

1. Verify the installation:

ansible --version

You should see the installed version of Ansible displayed in the output.

1.2. Installation on CentOS/RHEL

To install Ansible on a CentOS or RHEL system, follow these steps:

1. Enable the EPEL repository:

sudo yum install epel-release -y

1. Install Ansible:

sudo yum install ansible -y

1. Verify the installation:

ansible --version

1.3. Installation on macOS

For macOS users, Ansible can be installed using Homebrew:

1. Install Homebrew (if not already installed):"

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)

1. Install Ansible:

brew install ansible

1. Verify the installation:

ansible --version

2. Configuring Ansible

After installing Ansible, the next step is to configure it. The configuration file (ansible.cfg) is typically located in /etc/ansible/ or in the current working directory. Ansible also requires an inventory file to define the managed hosts.

2.1. Ansible Configuration File (ansible.cfg)

The ansible.cfg file allows you to configure various options such as inventory location, roles path, SSH timeout, and more. Below is an example of a basic ansible.cfg configuration:

[defaults]
inventory = ./hosts
remote_user = your-username
host_key_checking = False

2.2. Creating the Hosts Inventory File

The hosts inventory file is where you define the servers you want to manage. It can be a simple text file named hosts with groups and IP addresses. Below is an example:

[webservers]
192.168.1.10
192.168.1.11

[dbservers]
192.168.1.20
192.168.1.21

This configuration defines two groups of servers: webservers and dbservers. You can use these group names in your playbooks to target specific sets of servers.

3. Ansible Usage Examples

3.1. Running Ad-Hoc Commands

Ad-hoc commands are simple, one-off commands that you can run without writing a playbook. Here are some examples:

• Ping all hosts:

ansible all -m ping

• Check the disk space on all webservers:

ansible webservers -m shell -a "df -h"

• Install Apache on all webservers:

ansible webservers -m apt -a "name=apache2 state=present" -b

3.2. Writing and Running Playbooks

Playbooks are YAML files that define a series of tasks to be executed on remote servers. Below is a simple playbook to install Nginx on all webservers:

---
- name: Install Nginx on web servers
  hosts: webservers
  become: yes

  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present

To run this playbook, save it as install_nginx.yml and run the following command:

ansible-playbook install_nginx.yml

3.3. Using Variables in Playbooks

Variables make playbooks more flexible and reusable. You can define variables in the playbook or in a separate vars file. Here is an example:

---
- name: Install a web server
  hosts: webservers
  become: yes
  vars:
    http_port: 80

  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present
    - name: Ensure Nginx is running
      service:
        name: nginx
        state: started
        enabled: true

4. Managing Hosts Files

The hosts inventory file is critical for Ansible operations as it defines the target machines for automation. Hosts can be organized into groups, and variables can be assigned to hosts or groups to control behavior during playbook runs.

4.1. Defining Hosts with Variables

You can assign variables directly within the hosts file as shown below:

[webservers]
192.168.1.10 http_port=80 max_clients=200
192.168.1.11 http_port=8080 max_clients=150

[dbservers]
192.168.1.20 db_name=exampledb
192.168.1.21 db_name=testdb

4.2. Using Group Variables

Group variables can be defined in a directory called group_vars. For example, create a file named group_vars/webservers.yml and add:

---
http_port: 80
max_clients: 200

These variables are applied to all hosts in the webservers group.

Conclusion

Ansible provides a robust and flexible approach to managing server configurations and deployments. By understanding how to install and configure Ansible, create inventory files, write playbooks, and use variables, you can automate repetitive tasks and ensure consistency across your IT environment. This article offers a starting point for utilizing Ansible effectively, but its capabilities go much further, enabling complex orchestration and management of large-scale infrastructures.