Understanding Jenkinsfile, Ansible, and GitHub Actions Simplified.

#JENKINSFILE

pipeline {
    agent any

    environment {
        // Using SSH key stored in Jenkins credentials
        EC2_SSH_KEY = credentials('EC2_SSH')
        ANSIBLE_HOST_KEY_CHECKING = 'False'
    }

    stages {
        stage('Checkout') {
            steps {
                // Checkout the code from the GitHub repository
                checkout scm
            }
        }

        stage('Run Ansible Playbook') {
            steps {
                script {
                    // Running Ansible Playbook to configure the server
                    sh '''
                       ansible-playbook -i ./ansible/inventory.aws_ec2.yml -e 'host_group=tag_git_gitaction' ./ansible/playbooks/nginx-setup.yml -u ubuntu --private-key $EC2_SSH_KEY
                    '''
                }
            }
        }
    }
}

Explanation of the above jenkinsfile:

1. EC2_SSH_KEY = credentials('EC2_SSH') - This will bring the EC2_SSH credential from the jenkins credential to SSH on server which ansible is use.

2. steps {

   checkout scm
   } - This will clone the repo in the jenkins job workspace and search for jenkinsfile.

3. sh ''' ansible-playbook -i ./ansible/inventory.aws_ec2.yml -e 'host_group=tag_git_gitaction' ./ansible/playbooks/nginx-setup.yml -u ubuntu --private-key $EC2_SSH_KEY ''' - This will trigger the ansible to perform task by using inventory.aws_ec2.yml as inventory, nginx-setup.yml as playbook, host_group=tag_git_gitaction as a variable which will be used inside playbook.

---

ANSIBLE Inventory

#inventory.aws_ec2.yml-

plugin: aws_ec2
regions:
  - us-east-1
filters:
  "tag:git": "gitaction"
strict: true
keyed_groups:
  - prefix: tag
    key: tags

Work of ansible inventory is to search for the IPs of the basis of the filter you define in the inventory and provide them to the ansible playbook to perform tasks.

Explanation of the above ansible inventory:
1. regions: - us-east-1 - region is defined where to search.
2. filters: "tag:git": "gitaction" - tags defined in the EC2 tags.

---

ANSIBLE Playbook

#nginx-setup.yml - 

---
- name: Install and Configure Nginx
  hosts: "{{ host_group }}"
  become: yes
  tasks:
    - name: Install Nginx
      apt:
        name: nginx
        state: present

    - name: Start Nginx service
      systemd:
        name: nginx
        state: started
        enabled: yes

    - name: Remove default index.html
      file:
        path: /var/www/html/index.html
        state: absent

    - name: Clone custom HTML page from GitHub
      git:
        repo: 'https://github.com/<user-name>/<repo-name>'
        dest: /var/www/html
        clone: yes
        update: yes
        force: yes
    - name: Restart Nginx service
      systemd:
        name: nginx
        state: restarted

Explanation of the above ansible playbook:

1. hosts: "{{ host_group }}" - IP will be passed here by inventory.

2. Tasks of ansible-
   - name: Install Nginx

   - name: Start Nginx service

   - name: Remove default index.html
   - name: Clone custom HTML page from GitHub
   - name: Restart Nginx service