Why Your Code Works on Your Machine But Not on Mine (And How to Fix It)

---

Ever written code that works perfectly on your machine, only for it to break on someone else’s? You’re not alone.

Photo by Desola Lanre-Ologun on Unsplash

In a previous article, I discussed virtualization and how it optimizes infrastructure usage. But even with virtualization, developers still struggle with a common issue — environment inconsistencies.

John, a developer, just finished writing code for MyMediumBox and pushed it to GitHub. Mike, the operations engineer, pulled the code, installed dependencies, and tried deploying it to production. But instead of a smooth deployment, he got a dreaded error: “Build failed.".

Frustrated, Mike pings John on Slack: “Your code is broken.” John, confused, replies: “But it worked on my machine!

---

This problem happens everywhere in software development. Differences in dependencies, configurations, and operating systems can make software behave differently across environments. Differences in dependencies, configurations, and operating systems can make software behave differently across environments.

For example, an application designed to run on RHEL might fail when deployed on a Windows or macOS server due to missing system dependencies. Traditionally, developers had to rewrite or reconfigure their applications for each OS, which was time-consuming and frustrating.

With the introduction of Containerization, developer and operation team are now in sync and there has been a significant reduction of “it worked on my system” issues.

So, what is this containerization?

Containerization is the process of bundling an application and all its dependencies into a self-contained package called an image. This image can then run on any system without requiring manual setup or configuration to ensure consistency across different environments.

This means, John, the developer, can bundle the application “working on his system” into a portable, self-contain package. A package that have all the necessary requirement to run in production. Once packaged, this can then be sent to the Image Registry where both Test and Operation team can pull and run directly on any system.

This way, there is little to know configuration to do on the application except to describe the condition for it to run — such as port, network, name, volume, etc. Think of it like a shipping container in logistics: No matter what’s inside, the container fits seamlessly on ships, trucks, and trains without modification. Similarly, a containerized application runs consistently across different operating systems and infrastructure.

Why Should You Care? The Benefits of Containerization

• Eliminates “it works on my machine” issues — The same containerized app runs identically everywhere.

• Faster deployments — No need to manually set up dependencies on each machine.

• Scalability — Easily spin up multiple instances of an application across servers.

• Lightweight — Unlike virtual machines, containers share the host OS, making them fast and efficient.

• Portability — Move your application seamlessly between local development, testing, and production.

Gone are the days of dependency hell and broken deployments due to environment inconsistencies. Containerization solves these problems by packaging everything an application needs into a portable unit.

With Docker and Kubernetes, organizations can now deploy, scale, and manage applications effortlessly, making containerization a must-learn skill for developers and DevOps engineers.

So, the next time someone says, “It worked on my machine!”, you’ll know exactly why — and how to fix it. 🚀