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title: Ansible Tutorial 1: Concepts & Terminology tags: - ansible - tutorial - concepts - getting started

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Ansible Tutorial 1: Understand Ansible Concepts & Terminology

This tutorial introduces the core concepts and terminology of Ansible. It is the first step for anyone new to network automation or configuration management.

Ansible Overview

Ansible is an open-source automation tool for configuration management, application deployment, and task automation. It uses simple YAML files (playbooks) and does not require agents on managed nodes.

Introduction to YAML

YAML (YAML Ain't Markup Language) is a human-readable data format used for Ansible playbooks and inventories.

Example YAML:

key: value
list:
  - item1
  - item2

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Inventory

The inventory defines the hosts and groups Ansible manages. It is the foundation of all automation in Ansible.

Inventory File Formats

• INI format: Simple, easy to start with, good for small environments.
• YAML format: More powerful, supports nested groups and variables, recommended for larger or more complex environments.

Example inventory (INI):

[routers]
r1 ansible_host=192.0.2.1 ansible_user=admin ansible_password=yourpass ansible_network_os=ios
r2 ansible_host=192.0.2.2 ansible_user=admin ansible_password=yourpass ansible_network_os=ios

[switches]
s1 ansible_host=192.0.2.10 ansible_user=admin ansible_password=yourpass ansible_network_os=eos

Example inventory (YAML):

all:
  children:
    routers:
      hosts:
        r1:
          ansible_host: 192.0.2.1
          ansible_user: admin
          ansible_password: yourpass
          ansible_network_os: ios
        r2:
          ansible_host: 192.0.2.2
          ansible_user: admin
          ansible_password: yourpass
          ansible_network_os: ios
    switches:
      hosts:
        s1:
          ansible_host: 192.0.2.10
          ansible_user: admin
          ansible_password: yourpass
          ansible_network_os: eos

Host and Group Variables in Inventory

• You can define variables for all hosts, groups, or individual hosts directly in the inventory file or in separate group_vars/ and host_vars/ directories.
• Common variables include:
• ansible_host: The IP or DNS name to connect to
• ansible_user: The SSH username
• ansible_password: The SSH password
• ansible_network_os: The network platform (e.g., ios, eos, junos)
• ansible_become: Whether to use privilege escalation (e.g., enable mode)

Best Practice: - Use group_vars/ and host_vars/ for sensitive data and to keep your inventory clean and maintainable.

Example directory structure:

project/
  inventory.yml
  group_vars/
    routers.yml
    switches.yml
  host_vars/
    r1.yml
    s1.yml
  playbook.yml

Example group_vars/routers.yml:

ansible_user: admin
ansible_password: yourpass
ansible_network_os: ios

Example host_vars/r1.yml:

ansible_host: 192.0.2.1

Inventory Best Practices

• Use descriptive group names (e.g., routers, switches, firewalls)
• Store credentials and sensitive data in group_vars/ or use Ansible Vault for encryption
• Use YAML inventory for complex environments
• Document your inventory structure for your team

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ansible.cfg: Ansible Configuration File

The ansible.cfg file is the main configuration file for Ansible. It allows you to customize how Ansible behaves, set default paths, control privilege escalation, SSH settings, and more. Having a project-specific ansible.cfg in your project directory ensures consistent behavior for everyone working on the project.

Why use ansible.cfg? - Centralizes configuration for your project - Avoids the need to pass extra flags on every command - Ensures reproducible and predictable automation

Common settings: - inventory: Path to your inventory file - roles_path: Where Ansible looks for roles - host_key_checking: Disable SSH host key checking (useful for labs) - retry_files_enabled: Disable creation of retry files - remote_user: Default SSH user - private_key_file: Path to SSH private key - timeout: SSH connection timeout

Example ansible.cfg:

[defaults]
inventory = inventory.yml
roles_path = roles
host_key_checking = False
retry_files_enabled = False
remote_user = admin
private_key_file = ~/.ssh/id_rsa
timeout = 30

Tip: - Place your ansible.cfg in the root of your project directory. Ansible will automatically use it if present. - You can override any setting with command-line flags if needed.

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Ansible Playbook Structure

A playbook is a YAML file describing automation tasks.

Example playbook:

---
- name: Example Playbook
  hosts: routers
  gather_facts: no
  tasks:
    - name: Ping device
      ansible.builtin.ping:

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Host and Group Variables

Variables can be set for groups or individual hosts using group_vars/ and host_vars/ directories.

Example group_vars/routers.yml:

ansible_user: admin
ansible_password: yourpass
ansible_network_os: ios

Example host_vars/r1.yml:

ansible_host: 192.0.2.1

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Ansible Facts

Facts are variables automatically discovered about hosts. For network devices, use modules like cisco.ios.ios_facts or arista.eos.eos_facts.

Example:

- name: Gather facts from Cisco IOS
  hosts: routers
  gather_facts: no
  connection: network_cli
  tasks:
    - name: Get facts
      cisco.ios.ios_facts:
      register: facts
    - debug:
        var: facts

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Continue to Tutorial 2: Ansible Modules