🔐 How I Established SSH Connection Between Two AWS EC2 Instances

Abhishek Jha — Fri, 13 Jun 2025 17:37:37 +0000

Hey everyone! 👋

Today, I want to share a new concept I learned while working with AWS — establishing an SSH connection between two EC2 instances. It might sound simple, but it’s a foundational skill if you're diving deeper into networking, automation, or setting up multi-node systems like clusters, load balancers, or databases.

Let me walk you through the process, the purpose, and the lessons I picked up along the way!

🧾 Why I Did It

In real-world cloud infrastructure setups, different EC2 instances often need to communicate with each other — for example:

One EC2 acts as a controller or bastion host.
You need to run scripts remotely on another EC2 instance.
You're building a distributed application and want to pass data internally between nodes.

To do this securely, you set up an SSH connection from one EC2 to another using a private key.

⚙️ What I Did

Here’s the exact process I followed to set up SSH between two Ubuntu-based EC2 instances:

✅ Step 1: Create 2 EC2 Instances
I launched two EC2 instances in the same VPC and availability zone. Let's call them:

EC2-A (Source machine)
EC2-B (Target machine)

✅ Step 2: Copy EC2-B's Private Key to EC2-A
I securely copied the private key (PEM file) used to launch EC2-B into EC2-A using scp.

✅ Step 3: Adjust EC2-B's Security Group
In EC2-B's security group, I added an inbound rule to allow SSH (port 22) from EC2-A's private IP.

This ensures only EC2-A can initiate SSH connections to EC2-B — a best practice in cloud security.

✅ Step 4: SSH from EC2-A to EC2-B
Once everything was set, I SSHed into EC2-A and ran:

ssh -i "ec2-b-key.pem" ubuntu@<private-ip-of-ec2-b>

And boom 💥 — I was inside EC2-B from EC2-A!

🧩 Something I Faced

One issue I initially ran into:
Even after copying the PEM file and setting the correct permissions (chmod 400), I was getting "Permission denied (publickey)".

Turns out I hadn’t allowed EC2-A’s IP in EC2-B’s security group. Once I fixed that — the SSH worked like a charm.

📚 What I Learned

✅ How EC2 instances communicate within a private VPC
✅ Setting up secure SSH connections between two cloud servers
✅ Importance of security group configurations and IP restrictions
✅ Handling PEM keys and access control responsibly

This might seem like a small step, but it opens the door to bigger possibilities like:

Automating deployments from one EC2 to another
Setting up internal-only communication for microservices
Managing remote scripts or server orchestration

🧠 Final Thoughts

Cloud networking and EC2 configurations may look scary at first, but once you start doing it hands-on — it becomes clear, logical, and even fun.

If you're starting with AWS or EC2, I highly recommend practicing internal SSH setups — it’ll give you confidence in managing infrastructure securely and efficiently.

Thanks for reading! If this helped you or if you’ve done something similar, feel free to:

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Let’s keep exploring, experimenting, and learning! 🚀

🚀 How I Dockerized My Java Spring Boot App and Deployed It on AWS EC2

Abhishek Jha — Sat, 07 Jun 2025 19:20:31 +0000

Hey everyone! 👋

I recently completed a project that really leveled up my understanding of DevOps, Java backend development, and cloud deployment — and I wanted to share my experience in case you're starting your journey or exploring similar tools.

I built and deployed a full-stack Expenses Tracker Web App, where I used technologies like Spring Boot, Docker, Docker Compose, and AWS EC2. It’s the first time I’ve dockerized a real-world application and deployed it on a live server, and it taught me a ton about backend systems, containerization, and cloud environments.

Let me walk you through the journey, what I built, how I deployed it, the challenges I faced, and what I learned.

🧾 Project Overview: Expenses Tracker Web App

The goal was to create a simple but functional expense tracking system where users could:

Register and log in securely
Add, view, and delete their expenses
View a summary of their spending

🛠️ Technologies I Used

This project brought together several technologies across development and deployment:

Java and Spring Boot (core application logic)
Spring Security (for authentication)
Spring Data JPA + MySQL (for database integration)
Thymeleaf + Bootstrap (for frontend templating and styling)
Docker & Docker Compose (for containerization)
Amazon EC2 (Ubuntu) (for hosting the app)

Each of these played a key role in building a complete, modular, and scalable web application.

🐳 Dockerizing the Application

One of my main goals was to learn how to containerize a Java application using Docker. I created a Dockerfile that builds and runs the Spring Boot app, and used Docker Compose to spin up both the application and a MySQL database together in isolated containers.

This approach makes the app environment-independent and super easy to run on any server or system that supports Docker.

It also taught me how important it is to properly handle environment variables (like DB connection strings) for cleaner config management and better security.

☁️ Deploying on AWS EC2

Once my app was running smoothly in Docker locally, I moved to the cloud.

I launched an EC2 Ubuntu instance on AWS and installed Docker and Docker Compose. After pushing my project to GitHub, I cloned it into the EC2 server and ran everything using Docker Compose. I also configured AWS security groups to allow traffic on the correct ports.

In just a few steps, I had a live server running my app — all from the cloud. It felt amazing to see something I built locally available on a public IP address for the world to access.

🧩 A Problem I Faced (and Solved)

One interesting challenge I faced while working with Docker Compose was related to service-to-service communication.

At first, my Spring Boot app couldn’t connect to the MySQL container. After digging in, I realized the issue was that I was trying to connect using localhost instead of the Docker service name defined in the Compose file.

Once I changed the database hostname to match the service name (mysql in my case), the connection worked perfectly. It was a small but valuable lesson about how Docker networking works in multi-container setups.

📚 What I Learned

This project gave me hands-on experience with several critical concepts and tools that are extremely relevant in real-world software development:

✅ How to containerize a full-stack Java web application using Docker
✅ How to write and structure a Docker Compose file for multi-container setups
✅ The importance of environment variables and clean configuration
✅ How to launch and configure an EC2 instance on AWS
✅ Managing cloud infrastructure (ports, SSH, Docker setup)
✅ Debugging common DevOps and deployment issues

Most importantly, it taught me how to go from idea ➝ working app ➝ running cloud deployment — something I can now repeat and improve on with future projects.

🔗 Check Out the Project

The full source code is available on my GitHub:
👉 Dockerized-Expenses-Tracker-WebApp

Feel free to explore the code, run it yourself, or reach out if you have questions!

🎯 What’s Next?

I'm excited to keep building and improving. Here are a few things I want to work on next:

Add an Nginx reverse proxy for better scalability and HTTPS support
Explore CI/CD with GitHub Actions
Try PostgreSQL as an alternative DB engine
Learn about Kubernetes for orchestrating containers at scale
Create a frontend container and host both under a single domain

🧠 Final Thoughts

If you're just starting out with Docker, Java, or AWS, my advice is simple: build something real. You'll hit problems. You’ll read docs. You’ll break things. And then, you'll fix them — and learn deeply from the process.

Thanks for reading! If you enjoyed this, found it helpful, or have questions, feel free to:

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Let’s keep building, breaking, and learning 🚀

DEV Community: Abhishek Jha

🔐 How I Established SSH Connection Between Two AWS EC2 Instances

🧾 Why I Did It

⚙️ What I Did

🧩 Something I Faced

📚 What I Learned

🧠 Final Thoughts

🚀 How I Dockerized My Java Spring Boot App and Deployed It on AWS EC2

🧾 Project Overview: Expenses Tracker Web App

🛠️ Technologies I Used

🐳 Dockerizing the Application

☁️ Deploying on AWS EC2

🧩 A Problem I Faced (and Solved)

📚 What I Learned

🔗 Check Out the Project

🎯 What’s Next?

🧠 Final Thoughts