🚀 JENKINS FULL END-TO-END TUTORIAL

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🧱 1. What is Jenkins?

Jenkins is an open-source automation server used to:

• Build and test your code continuously (CI)

• Deploy applications automatically (CD)

• Orchestrate DevOps pipelines (with Docker, Kubernetes, etc.)

It supports plugins for everything — GitHub, Docker, SonarQube, AWS, ArgoCD, etc.

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🧰 2. System Requirements

Requirement	Recommended
OS	Ubuntu 20.04 / 22.04 (or Windows)
RAM	4 GB minimum
Java	Java 11+ (JDK 17 preferred)
Browser	Chrome / Firefox

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⚙️ 3. Jenkins Installation (Ubuntu)

Step 1: Update packages

sudo apt update && sudo apt upgrade -y

Step 2: Install Java

sudo apt install openjdk-17-jdk -y

Step 3: Add Jenkins repository and key

curl -fsSL https://pkg.jenkins.io/debian/jenkins.io.key | sudo tee \
  /usr/share/keyrings/jenkins-keyring.asc > /dev/null

echo deb [signed-by=/usr/share/keyrings/jenkins-keyring.asc] \
  https://pkg.jenkins.io/debian binary/ | sudo tee \
  /etc/apt/sources.list.d/jenkins.list > /dev/null

Step 4: Install Jenkins

sudo apt update
sudo apt install jenkins -y

Step 5: Start Jenkins

sudo systemctl start jenkins
sudo systemctl enable jenkins

Step 6: Access Jenkins

Go to →
👉 http://localhost:8080

Get the initial admin password:

sudo cat /var/lib/jenkins/secrets/initialAdminPassword

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🧩 4. Setup Wizard

1. Paste the admin password.

2. Choose “Install suggested plugins”.

3. Create your admin user.

4. You’ll land on the Jenkins Dashboard.

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🧱 5. Jenkins Architecture Overview

Developer → Git Push → Jenkins Pipeline → Build → Test → Deploy

Key Components:

Component	Description
Jenkins Master	Orchestrates builds and manages agents
Agent/Node	Executes the actual build steps
Pipeline	Script that defines your CI/CD flow
Job	Unit of work (can be Freestyle or Pipeline)
Workspace	Directory on agent where build happens

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🧩 6. Jenkins Plugins (Essential Ones)

Go to: Manage Jenkins → Plugins → Available
Search & Install:

✅ Git
✅ Docker
✅ Pipeline
✅ Blue Ocean (modern UI)
✅ Kubernetes
✅ Snyk Security (optional)

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🏗️ 7. Example Project: CI/CD Pipeline for a Python Web App

Let’s say your repo structure is:

my-app/
├── app.py
├── requirements.txt
├── Dockerfile
└── Jenkinsfile

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Step 1: Dockerfile

FROM python:3.11-slim
WORKDIR /app
COPY . /app
RUN pip install -r requirements.txt
CMD ["python", "app.py"]

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Step 2: Jenkins Pipeline (Jenkinsfile)

Create a file named Jenkinsfile in your repo:

pipeline {
    agent any

    environment {
        DOCKER_HUB_USER = credentials('dockerhub-credentials')
        IMAGE_NAME = "yuvaraj/my-app"
    }

    stages {
        stage('Checkout Code') {
            steps {
                git branch: 'main', url: 'https://github.com/yuvaraj/my-app.git'
            }
        }

        stage('Install Dependencies') {
            steps {
                sh 'pip install -r requirements.txt'
            }
        }

        stage('Run Tests') {
            steps {
                sh 'pytest || echo "Tests Skipped"'
            }
        }

        stage('Build Docker Image') {
            steps {
                script {
                    sh "docker build -t $IMAGE_NAME:${env.BUILD_NUMBER} ."
                }
            }
        }

        stage('Push to Docker Hub') {
            steps {
                script {
                    sh "echo $DOCKER_HUB_USER_PSW | docker login -u $DOCKER_HUB_USER_USR --password-stdin"
                    sh "docker push $IMAGE_NAME:${env.BUILD_NUMBER}"
                }
            }
        }

        stage('Deploy to Kubernetes') {
            steps {
                script {
                    sh 'kubectl apply -f k8s/deployment.yaml'
                }
            }
        }
    }

    post {
        always {
            echo "Pipeline finished: ${currentBuild.currentResult}"
        }
    }
}

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Step 3: Create Jenkins Credentials

Go to:

Manage Jenkins → Credentials → Global → Add Credentials

Add:

• Docker Hub Username/Password

• Kubernetes Kubeconfig (if you’re deploying to a cluster)

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Step 4: Create Pipeline Job

1. Go to Jenkins Dashboard

2. Click “New Item” → Pipeline

3. Name: my-app-pipeline

4. Under Pipeline → Choose Pipeline script from SCM

5. Select Git, paste repo URL, branch = main

6. Save & Run ✅

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Step 5: Watch Pipeline in Action

You’ll see stages like:

[1] Checkout Code
[2] Install Dependencies
[3] Run Tests
[4] Build Docker Image
[5] Push to Docker Hub
[6] Deploy to Kubernetes

If all succeed → Jenkins deploys automatically 🎉

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🧠 8. Jenkins Pipeline Types

Type	Description
Declarative Pipeline	Easier syntax (recommended for beginners)
Scripted Pipeline	Fully Groovy-based, more flexible

Example:

pipeline {
  agent any
  stages {
    stage('Build') { steps { echo 'Building...' } }
  }
}

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🔐 9. Integrations

Tool	Integration
GitHub Webhook	Auto-trigger Jenkins when new code is pushed
Slack	Send build notifications
SonarQube	Code quality analysis
Trivy / Snyk	Container security scanning
AWS / GCP	Deploy using Jenkins pipelines

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📊 10. Jenkins + GitHub Webhook Setup

1. Go to your GitHub repo → Settings → Webhooks → Add webhook

• Payload URL: http://<your-server-ip>:8080/github-webhook/

• Content type: application/json

• Trigger: “Just the push event”

Now every push triggers Jenkins automatically 🚀

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🧩 11. Jenkins + Docker Integration

Install Docker plugin and ensure Jenkins user can run Docker:

sudo usermod -aG docker jenkins
sudo systemctl restart jenkins

Verify inside Jenkins:

docker ps

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🧠 12. Jenkins + Kubernetes (Optional)

If you have Kubernetes (like Minikube or AWS EKS):

• Create k8s/deployment.yaml

• Use Jenkins kubectl apply -f step

• You can even run Jenkins inside Kubernetes with a Helm chart.

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🪶 13. Monitoring Jenkins

• URL: http://localhost:8080/monitoring

• Integrate Prometheus plugin

• View build metrics and job status in Grafana dashboards.

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🧩 14. Best Practices

✅ Store pipeline code in Jenkinsfile (GitOps-style).
✅ Use credentials from Jenkins Secret Store.
✅ Keep stages modular: build, test, deploy, notify.
✅ Use Docker agents for isolated builds.
✅ Enable security: disable anonymous access.
✅ Use backup plugin or external volume for /var/lib/jenkins.

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⚡ 15. Sample Real-World Flow

Developer → Git Push →
GitHub Webhook triggers Jenkins →
Build + Test →
Docker Image →
Push to Docker Hub →
Deploy to Kubernetes →
Prometheus + Grafana monitor app →
Slack notification sent.

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