🚀 Day 17: Dockerfile – First DevOps Project with Docker 🚀

Hey there, DevOps enthusiasts! 👋 Welcome to Day 17 of the #90DaysOfDevOps challenge. Today, we're diving into Docker and exploring the magical world of the Dockerfile. By the end of this blog, you'll have a shiny new Dockerized web app ready to flaunt. Let’s get started! 🛠️

What is a Dockerfile? 🐳

Think of a Dockerfile as a recipe 🧑‍🍳 for building your application into a container. It contains step-by-step instructions that Docker follows to create a lightweight, portable environment for your app.

Imagine you're making a pizza 🍕:

• The base image is the dough 🫓.

• The instructions (like "bake for 10 minutes") are the Docker commands.

• The result? A containerized app that works perfectly anywhere! 🌍

Here’s how a Dockerfile works:

1. Start with a base image: A pre-made environment (e.g., Python, Node.js, etc.).

2. Add your app: Copy your code, dependencies, and settings.

3. Define the run command: Tell Docker how to start your app.

Understanding the Key Components of a Dockerfile

Let’s break it down using an example for a Python Flask web app:

1. Base Image 🧱

FROM python:3.9-slim

This tells Docker, "Hey, I want to use Python 3.9 as my base environment!"

2. Set Working Directory 🗂️

WORKDIR /app

It creates a folder called /app inside the container and sets it as the default working directory.

3. Copy Dependencies 📄

 COPY requirements.txt requirements.txt

This copies the requirements.txt (which lists Python packages) into the container.

4. Install Dependencies ⚙️

 RUN pip install --no-cache-dir -r requirements.txt

This installs all the Python libraries your app needs to run.

5. Copy Your App Code 🖥️

COPY . .

It copies your application code into the container.

6. Expose a Port 🌐

 EXPOSE 5000

This opens port 5000 so we can access the app.

7. Define the Start Command ▶️

CMD ["python", "app.py"]

This tells Docker to run app.py when the container starts.

Let’s Build a Project: Dockerized Flask App 🐍

We’re creating a simple Flask app, containerizing it with Docker, and publishing it to Docker Hub. Follow these steps:

1. Build the App Code 🖋️

• Create a file called app.py:

    from flask import Flask
  
    app = Flask(__name__)
  
    @app.route('/')
    def home():
        return "Hello, World! 🚀 Welcome to the Dockerized Flask App."
  
    if __name__ == "__main__":
        app.run(host="0.0.0.0", port=5000)
  

  

  Add a requirements.txt file:

    flask
  

  

  2. Create the Dockerfile 📃

    # Use Python 3.9 base image
    FROM python:3.9-slim
  
    # Set the working directory
    WORKDIR /app
  
    # Copy dependencies
    COPY requirements.txt requirements.txt
  
    # Install dependencies
    RUN pip install --no-cache-dir -r requirements.txt
  
    # Copy app code
    COPY . .
  
    # Expose port
    EXPOSE 5000
  
    # Run the application
    CMD ["python", "app.py"]
  

  

  3. Build the Docker Image 🛠️

  Run this command in your terminal:

    docker build -t flask-app .
  

  4. Run the Docker Container 🏃‍♂️

  Start the container:

    docker run -d -p 5000:5000 flask-docker-app
  

  

  5. Test the App 🌐

  Open your browser and visit:
  👉 http://localhost:5000
  You’ll see:
  Hello, World! 🚀 Welcome t``o the Dockerized Flask App.

  

  6. Push to Docker Hub 🚢

  1. Log in to Docker Hub:

      docker login
     

  2. Tag your image:

      docker tag flask-docker-app chintamani1804/flask-app:latest
     

  3. Push the image:

      docker push chintamani1804/flask-app:latest
     

  4. Check your Docker Hub repository to see your app image live! 🎉

Step 5: Clean Up

Stop the container and remove the image (optional):

    docker stop <container-id>
    docker rm <container-id>
    docker rmi flask-docker-app

Why is this Project Important? 🤔

This project demonstrates:

• Containerization: You’ve packaged your app to run anywhere.

• DevOps Workflow: You’ve learned how to push images to Docker Hub.

• Web Development + Docker Skills: A great combination for your resume!

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Takeaways 💡

1. Docker simplifies application deployment and scaling.

2. A Dockerfile is a must-have skill for any DevOps engineer.

3. Pushing images to Docker Hub makes your project easily shareable.

Keep going strong on your #90DaysOfDevOps journey. You’re doing amazing! 💪
Let me know how your project turned out in the comments below! 😊