Jenkins & CI/CD — Week 3 & 4

Introduction to Jenkins

Jenkins is an open-source automation server used to implement Continuous Integration (CI) and Continuous Deployment (CD). It allows users to create different types of jobs to automate tasks like building, testing, and deploying applications.

Key Point Jenkins is the most widely used CI/CD tool in DevOps. It connects your code repository (GitHub) with your build tools (Maven) and deployment targets (Tomcat, Docker).

Freestyle Job

A Freestyle job is the simplest Jenkins job type. It allows you to configure build steps through the Jenkins UI without writing code. It is mainly used for basic automation tasks.

Steps to Create a Freestyle Job

Open Jenkins dashboard in browser — http://<server-ip>:8080
Click New Item
Enter a job name
Select Freestyle project → Click OK
In Source Code Management, select Git and provide repository URL
In Build Steps, click Add build step → Execute shell
Enter build commands like mvn clean install
Click Save → Build Now to run the job

Pipeline Job

A Pipeline job defines the entire build and deployment process as code using a Jenkinsfile. It provides better automation, version control, and complex workflow management.

Steps to Create a Pipeline Job

Open Jenkins dashboard → New Item
Enter a job name → Select Pipeline → Click OK
Scroll to Pipeline section → Choose Pipeline script from SCM
Select SCM as Git → Enter the GitHub repository URL
Specify the branch (e.g., main or master)
Set Script Path as Jenkinsfile
Click Save → Build Now

Jenkinsfile Location The Jenkinsfile must be committed in the root of your GitHub repository. Jenkins pulls it automatically when the pipeline runs.

Freestyle vs Pipeline Jobs

Feature	Freestyle Job	Pipeline Job
Configuration	Via Jenkins UI	Defined as code in Jenkinsfile
Use case	Simple builds	Complex CI/CD workflows
Version control	Hard to version control	Easily version controlled with Git
Flexibility	Limited	Highly flexible and scalable
Recommended for	Beginners / learning	Production CI/CD pipelines

CI/CD Pipeline for Java Web Application

Aim: Automate the build and deployment of a Java Maven web application using Jenkins and deploy it to Apache Tomcat on AWS Ubuntu.

Tools & Architecture

Tool	Role
Java 17	Programming language runtime
Apache Maven	Build and dependency management
Jenkins	CI/CD automation server
Apache Tomcat	Web server to run WAR file
GitHub	Source code repository
AWS EC2 Ubuntu	Cloud server environment

Architecture Flow Developer → GitHub → Jenkins → Maven Build → WAR file → Tomcat → Browser

Step-by-Step Procedure

Step 1: Install Java 17

sudo apt update
sudo apt install openjdk-17-jdk -y
java -version

Step 2: Install Maven

sudo apt install maven -y
mvn -v

Step 3: Install Jenkins

sudo apt update
sudo apt install jenkins -y
sudo systemctl enable jenkins
sudo systemctl start jenkins
sudo systemctl status jenkins
# Access Jenkins at http://<EC2-IP>:8080

Step 4: Install and Configure Tomcat

sudo apt install tomcat10 tomcat10-admin -y

Port Conflict Jenkins and Tomcat both default to port 8080. Change Tomcat's port to 8090 to avoid conflict.

# Edit Tomcat server config
sudo nano /etc/tomcat10/server.xml
# Find: <Connector port="8080" protocol="HTTP/1.1"
# Change to: <Connector port="8090" protocol="HTTP/1.1"

Reference Repository Fork this repo for a working Jenkinsfile and Dockerfile:
https://github.com/syoganandh/spring-boot-maven-example-helloworld.git

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Jenkins & CI/CD — Notes PDF

Week 3 & 4 · Freestyle Jobs, Pipeline Jobs, Maven & Tomcat

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