ansible-learning

Weekly Journals :

• Session 1 - Introduction & Setting up of Ansible
• Session 2 - Complete overview of Playbook
• Session 3 - Ansible configuration file & Ansible Facts
• Session 4 - Installing & Configuring of Docker with Ansible
• Session 5 - Template & Jinja2
• Session 6 - Setting up load balancer & Ansible Roles

Extras

• Github Markdown TOC Generator

Ansible Hands-on Guide for Beginners

1. Introduction to Ansible

Ansible is an open-source automation tool used for configuration management, application deployment, and task automation. It is agentless and uses SSH to communicate with remote machines.

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2. Removing Unnecessary Software

Before starting, remove any unnecessary software like firefox, php, and httpd.

Command:

sudo yum remove -y firefox php httpd

Explanation:

• yum remove → Removes the specified packages.
• -y → Automatically confirms removal without asking.
• firefox php httpd → List of packages to be removed.

Verify Removal:

rpm -q firefox php httpd

• This command checks if the packages are still installed.
• If a package is not installed, it will return: package <name> is not installed.

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3. Understanding Ansible Inventory Structure

Ansible uses an inventory file (/etc/ansible/hosts) to manage hosts.

Edit the Inventory File:

gedit /etc/ansible/hosts

Example Inventory File Content:

[local]
localhost ansible_connection=local

[webservers]
192.168.1.10
192.168.1.11

Explanation:

• [local] → Defines a local group.
• localhost ansible_connection=local → Configures Ansible to run locally.
• [webservers] → Defines a group for web servers.
• IPs 192.168.1.10 & 192.168.1.11 are the managed nodes.

To list all hosts in inventory:

ansible all --list-hosts

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4. Running Ad-hoc Ansible Commands

Ad-hoc commands are one-time Ansible commands that don't require a playbook.

Test Connectivity with Hosts:

ansible all -m ping

Expected Output:

localhost | SUCCESS => {
    "ping": "pong"
}

Run Shell Commands on Remote Hosts:

ansible all -m command -a "whoami"

ansible all -m command -a "date"

Explanation:

• ansible all → Runs the command on all hosts in the inventory.
• -m command → Uses the command module to execute shell commands.
• -a "whoami" → Executes the whoami command to check the logged-in user.

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5. Installing and Managing Packages via Ansible

Install httpd (Apache Web Server):

ansible all -m package -a "name=httpd state=present"

Install dialog as Root (With Sudo Privileges):

ansible all -m package -a "name=dialog state=present" \
  --become --become-method=sudo --become-user=root --ask-become-pass

Understanding Different States in Ansible Modules

State	Description
present	Ensures the package is installed.
absent	Ensures the package is removed.
latest	Ensures the package is installed with the latest version.
installed	Alias for present.
removed	Alias for absent.

Commonly Used Ansible Modules

Module	Purpose
ping	Checks connectivity with hosts.
command	Runs shell commands on remote hosts.
package	Installs, removes, or manages packages.
copy	Copies files from the control node to remote hosts.
service	Manages services (start, stop, restart, enable).
firewalld	Configures firewall rules.

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6. Ansible Playbooks

Playbooks are YAML files that define a set of tasks to automate complex processes.

Example Playbook: Install and Start Apache

- hosts: webservers
  become: yes
  tasks:
    - name: Install Apache
      package:
        name: httpd
        state: present
    
    - name: Start Apache Service
      service:
        name: httpd
        state: started
        enabled: yes

Explanation:

• hosts: webservers → Applies tasks to the webservers group.
• become: yes → Uses root privileges.
• package: → Installs Apache (httpd).
• service: → Starts and enables Apache.

Run the Playbook:

ansible-playbook apache.yml

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7. Summary of Useful Ansible Commands

Command	Description
ansible all -m ping	Check if hosts are reachable
ansible all -m command -a "whoami"	Check the user running Ansible on remote machines
ansible all --list-hosts	Show all managed hosts
ansible all -m command -a "date"	Get the current date on all hosts
ansible all -m package -a "name=httpd state=present"	Install httpd using Ansible
ansible all -m package -a "name=dialog state=present" --become --ask-become-pass	Install dialog with sudo privileges
ansible-playbook apache.yml	Run an Ansible playbook

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