Setting up Jenkins on an AWS EC2 instance allows you to automate your software development processes efficiently. This guide provides a detailed, step-by-step approach to launching an EC2 instance, installing Jenkins, and configuring it for your CI/CD needs.

Table of Contents:

Prerequisites
Step 1: Launch an EC2 Instance
Step 2: Connect to Your EC2 Instance via SSH
Step 3: Install Java
Step 4: Install Jenkins
Step 5: Configure Security Groups
Step 6: Access Jenkins Web Interface
Step 7: Create a Jenkins Job
Conclusion

Prerequisites

AWS Account: Ensure you have an active AWS account. If not, sign up here.
Basic Knowledge: Familiarity with AWS services and command-line operations is beneficial.

Step 1 — Launch an EC2 Instance

Log in to AWS: Access the AWS Management Console.
Navigate to EC2 Dashboard:
- In the Services menu, select EC2 under Compute.
Launch Instance:
- Click on Launch Instance.
- Name and Tags: Assign a name to your instance (e.g., "Jenkins-Server").
- Application and OS Images (Amazon Machine Image): Choose Amazon Linux 2 AMI (HVM), SSD Volume Type.
- Instance Type: Select t2.micro (eligible for free tier).
- Key Pair (Login):
  - Create a new key pair or select an existing one.
  - If creating new, download the .pem file and store it securely; you'll need it to access your instance.
- Network Settings:
  - Create a new security group with the following inbound rules:
    - SSH (port 22): Allows secure shell access.
    - HTTP (port 80): Enables web traffic.
    - Custom TCP (port 8080): Required for Jenkins access.
- Configure Storage: The default storage configuration is typically sufficient.
- Launch: Review all settings and click Launch Instance.
Verify Instance Status:
- Return to the EC2 Dashboard.
- Ensure your instance's Instance State is running.

Step 2 — Connect to Your EC2 Instance via SSH

Set Key Permissions:
- Open your terminal.
- Modify the permissions of your key pair file to ensure it's not publicly viewable:

chmod 400 /path/to/your-key-pair.pem

Retrieve Public IP:
- In the EC2 Dashboard, select your instance.
- Note the Public IPv4 address listed in the instance details.
Establish SSH Connection:
- Use the following command, replacing /path/to/your-key-pair.pem with the path to your key pair file and ec2-user@your-public-ip with the appropriate username and IP address:

ssh -i /path/to/your-key-pair.pem ec2-user@your-public-ip

For example:

ssh -i ~/.ssh/jenkins-key.pem ec2-user@54.123.45.67

Step 3 — Install Java

Jenkins requires Java to run. Follow these steps to install Java 17:

Update Packages:

sudo yum update -y

Install Java 17:

sudo yum install java-17-amazon-corretto -y

Verify Installation:

java -version

Expected output:

openjdk version "17.0.x" 2023-xx-xx
OpenJDK Runtime Environment Corretto-17.0.x.x.x (build 17.0.x+xx)
OpenJDK 64-Bit Server VM Corretto-17.0.x.x.x (build 17.0.x+xx, mixed mode)

Step 4 — Install Jenkins

Add Jenkins Repository:

sudo wget -O /etc/yum.repos.d/jenkins.repo https://pkg.jenkins.io/redhat-stable/jenkins.repo

Import Jenkins GPG Key:

sudo rpm --import https://pkg.jenkins.io/redhat-stable/jenkins.io-2023.key

Install Jenkins:

sudo yum install jenkins -y

Enable Jenkins Service:

sudo systemctl enable jenkins

Start Jenkins Service:

sudo systemctl start jenkins

Check Jenkins Status:

sudo systemctl status jenkins

Ensure the output indicates that Jenkins is active (running).

Step 5 — Access Jenkins Web Interface

Open a browser and navigate to:

http://<public-ip-address>:8080

Replace <public-ip-address> with your EC2 instance's public IP.

Retrieve the initial admin password:

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

Copy the password and paste it into the Jenkins setup page.

Install suggested plugins and create your admin user.

Step 6 — Create a Jenkins Job

From the Jenkins dashboard, click New Item.
Name the job (e.g., "Hello-World") and select Freestyle Project.
Scroll down to the Build Environment section and check "Delete workspace before build starts."
Under Build Steps, click Add build step > Execute Shell, and enter:

echo "Hello, World!"

Save and click Build Now.
Check the console output to see "Hello, World!" printed.

Conclusion

Congratulations! You’ve successfully set up Jenkins on an AWS EC2 instance, accessed its web interface, and created a simple Jenkins job. Jenkins is a versatile tool that supports complex CI/CD workflows, making it invaluable for software development teams.

Feel free to explore plugins and additional configurations to tailor Jenkins to your project's needs.