Docker: Install, Run, and Test Your First Container - DotNet series

Introduction

Welcome to the first article in our Docker with .NET series! Throughout this series, we’ll explore how Docker simplifies development, deployment, and scalability in .NET applications.

The End of "Works on My Machine" Excuses

You know that classic developer dilemma?

• Developer: It works fine on my machine!"
• QA: Well, we're not giving your machine to the client.

Then, the moment you deploy your code to production, everything breaks. At that point, you start wondering... Can I just throw my machine into production?

Well, Docker makes that wish come true! Think of Docker as a virtual suitcase where you can pack your OS, software, code, libraries, and everything your application needs to run. Once everything works inside that suitcase, you can push it to production without worrying about missing dependencies or environment differences.

And just like that, the age-old "It works on my machine!" issue is solved because now, your suitcase (or at least a copy of it) can be thrown into production!

This suitcase that contains everything your app needs is called a container.

Why Use Docker?

Docker has become one of the most popular tools in modern software development. But why should you use it?

• Portability: Docker containers run the same way regardless of the operating system (Windows, macOS, Linux, cloud, on-prem). This ensures that an application tested on a developer’s laptop will work identically on a production server.
• Efficiency & Lightweight: Since Docker containers share the host OS kernel, they use fewer system resources compared to VMs. This allows running more applications on the same infrastructure.
• Scalability: Docker makes it easy to scale applications horizontally by deploying multiple instances of a containerized app. It integrates well with orchestration tools like Kubernetes and Docker Swarm for automated scaling.
• Fast Deployment & Testing: Containers can be created, started, and destroyed within seconds; this makes it easy to test applications and quickly deploy updates.
• Isolation: Each container runs independently, ensuring that dependencies do not conflict between applications. This is particularly useful when running different versions of the same software on a single system.

Docker is widely used.

• Microservices Architecture: Running and managing multiple services.
• CI/CD Pipelines: Automating builds, testing, and deployment.
• Cloud Deployment: Making apps cloud-ready for AWS, Azure, and GCP.

Docker Terminology

1. Docker Image - Coffee Recipe
   • A Docker image is like a recipe that tells how to make a container. It includes everything needed to run an app, like the operating system, software, and code.
   • Like a coffee recipe. It has all the instructions and ingredients needed to make a perfect cup of coffee (application).
2. Docker Container - A Cup of Coffee
   • A container is a working copy of a Docker image.
   • Like a real cup of coffee. You can make multiple cups from the same recipe, just like you can run multiple containers from the same image.
3. Dockerfile - Written Coffee Recipe
   • A Dockerfile is a text file that contains instructions to build a Docker image.
   • Like a written recipe for your coffe8e. It tells the barista (Docker) exactly how to make it step by step.
4. Docker Compose - Coffee Order for a Group
   • Docker Compose is a tool to define and run multiple containers together.
   • Like placing a group order at a café. Instead of ordering each coffee separately, you give one order slip with details for multiple drinks (containers).
5. Docker Hub - Recipe Book
   • Docker Hub is a cloud-based registry where Docker images are stored and shared.
   • So it is like a public cookbook where you can find and share coffee recipes (Docker images) with others.
6. Volume - Reusable Coffee Mug
   • A volume is extra storage for a container that keeps data safe, even if the container stops.
   • Like a reusable coffee mug. Even if you throw away the coffee (stop the container), the mug (data) remains for the next time you make a new cup.
7. Docker Client - Customer Placing the Order
   • The Docker Client is like the customer ordering coffee. They give instructions (via CLI or GUI) to tell the barista what they want.
8. Docker Daemon - Barista Making the Coffee
   • The Docker Daemon is the barista working in the background. It takes the order from the customer (client) and prepares the coffee (runs the container).

Installing Docker and Running Your First Container
 

Step 1. Downloading docker

• Visit the official Docker website.
• Download Docker Desktop for your operating system (Windows or macOS). Refer to the image below to see all the platforms currently supported by Docker.
  
  Image 1. Downloading Docker from the Official Website

Step 2. Install and Launch Docker Desktop

• Open the downloaded installer and follow the on-screen instructions to install Docker Desktop.
  
  Image 2. Installing Docker Desktop
• Once installed, launch Docker Desktop. Sign in with your Docker Hub account (or create one if you don’t have an account).
  
  Image 3. Creating a Docker Hub Account
  
  Image 4. Starting the Docker Daemon

Step 3. Verify Installation

1. Open a Command Prompt (Windows) or Terminal (macOS).
2. Run the following command to check if Docker is installed and working.

   docker --version
   

3. This should display the installed Docker version.
   

Step 4. Run a Test Container

To verify that Docker can pull and run containers, execute.

docker run hello-world

What does this do?

• Pulls the "hello-world" image from Docker Hub (if not already available).
• Run a test container from the image.
• Displays a message confirming that Docker is working correctly.
  
  Image 5. Running Your First Docker Container

Congratulations! You’ve successfully installed Docker and run your first container. This is a simple test to verify that Docker can pull images and run containers.

Conclusion

By now, you should have a clearer understanding of how Docker solves the age-old "It works on my machine!" problem.

Stay tuned for the next articles in the series, where we'll dive deeper into containerizing .NET applications, working with Docker Compose, and more.

Docker is a powerful tool that enhances development process, making deployments faster. With Docker, you’ll ensure that your applications runs everywhere, from your local machine to production servers.

Keep exploring, and happy Dockerizing!