Ansible Study Notes - 01

What is Ansible?

Ansible is an open-source automation tool designed to simplify IT infrastructure management, application deployment, and task automation.

Before diving into Ansible, let's familiarize ourselves with some core concepts:

• Control node: A machine where Ansible is installed and commands are executed. From the control node, we can manage and operate multiple machines.
• Managed node: The remote machine or target being managed. These are the servers or devices you wish to operate on.
• Inventory: A way to group managed machines for easier management.
• Playbook: A blueprint for automation, defining and orchestrating the tasks to be performed.

---

Getting Started

Let’s write a simple Ansible script to experience the basics of Ansible.

Prerequisites

• A machine (Linux/Windows/macOS), either a PC or a server
• A Linux or Windows server

---

Installing Ansible

First, we need to install Ansible on the control node.

Check Python Version

Run one of the following commands:

python3 -V

or

python -V

Sample output:

Python 3.9.18

note

Ansible requires Python 3.

tip

On Rocky Linux 9, the default version is Python 3.9.x.

Verify pip Installation

Run:

python3 -m pip -V

If pip is installed, you’ll see its version:

pip 21.2.3 from /usr/local/lib/python3.9/site-packages/pip (python 3.9)

If not, you'll see an error:

/bin/python3: No module named pip

To install pip:

python3 -m ensurepip --default-pip

Example output:

Successfully installed pip-21.2.3

Install Ansible

Run the following command:

python3 -m pip install --user ansible

Install the pywinrm Module

If you plan to manage Windows servers with Ansible, install the pywinrm module:

python3 -m pip install pywinrm

---

Creating an Inventory

What Is an Inventory File?

An inventory file in Ansible defines the hosts to manage and their connection details. It is typically written in YAML or INI format and specifies the machines Ansible will manage and how to connect to them.

Inventory files include:

• Host groups: Categories like windows or linux.
• Hosts: Specific machines or servers, including connection details.

Create an inventory.yaml file as follows:

windows:
  hosts:
    win01:
      ansible_host: 1.1.1.2
      ansible_user: username
      ansible_password: password
      ansible_connection: winrm
      ansible_winrm_transport: basic
      ansible_winrm_server_cert_validation: ignore
    win02:
      ansible_host: 1.1.1.3
      ansible_user: username
      ansible_password: password
      ansible_connection: winrm
      ansible_winrm_transport: basic
      ansible_winrm_server_cert_validation: ignore

linux:
  hosts:
    linux01:
      ansible_host: 1.1.1.5
      ansible_user: username

Key details:

• windows and linux are group names.
• win01, win02, and linux01 are hostnames.
• Ansible keywords:
  • ansible_user: The username for connection.
  • ansible_password: The password for connection.
  • ansible_connection: Connection type (e.g., SSH or WinRM).

note

Linux hosts don’t require ansible_password if you use SSH keys. If SSH keys are not set up, you can provide a password instead.

Verify Inventory Syntax

Run:

ansible-inventory -i inventory.yaml --list

You should see output like this:

{
  "all": {
    "children": ["ungrouped", "windows", "linux"]
  },
  "windows": {
    "hosts": ["win01", "win02"]
  },
  "linux": {
    "hosts": ["linux01"]
  }
}

tip

all and ungrouped are default Ansible groups. Hosts without explicit groups are assigned to ungrouped.

Test Connectivity

Run:

ansible windows -m win_ping -i inventory.yaml
ansible linux -m ping -i inventory.yaml

Sample output:

win01 | SUCCESS => { "ping": "pong" }
linux01 | SUCCESS => { "ping": "pong" }

---

Writing a Playbook

A playbook is a collection of instructions and logic for tasks to execute on servers.

Here’s an example playbook.yaml:

- name: Upload file to Windows servers
  hosts: windows
  tasks:
    - name: Check if file exists
      ansible.builtin.win_stat:
        path: "C:\\Users\\test\\file.txt"
      register: file_stat

    - name: Upload file if not present
      ansible.builtin.win_copy:
        src: "file.txt"
        dest: "C:\\Users\\test\\file.txt"
      when: not file_stat.stat.exists

- name: Upload file to Linux servers
  hosts: linux
  tasks:
    - name: Check if file exists
      ansible.builtin.stat:
        path: "/home/test/file.txt"
      register: file_stat

    - name: Upload file if not present
      ansible.builtin.copy:
        src: "file.txt"
        dest: "/home/test/file.txt"
      when: not file_stat.stat.exists

Explanation

1. Windows Section:

   • Checks if the file exists using win_stat and registers the result.
   • Uploads the file only if it doesn’t exist (when: not file_stat.stat.exists).

2. Linux Section:

   • Uses the stat module to check the file status.
   • Copies the file conditionally if it’s missing.

Run the Playbook

Place a file.txt in the same directory and execute:

ansible-playbook playbook.yaml -i inventory.yaml

Output:

PLAY [Upload file to Windows servers] ...

TASK [Upload file if not present] ...
changed: [win01]

PLAY [Upload file to Linux servers] ...

TASK [Upload file if not present] ...
changed: [linux01]

You’ve now successfully executed a basic Ansible script!

Happy Coding! 🎉