This content originally appeared on DEV Community and was authored by Yash Sonawane
🎬 "Ready to become a Docker chef? In this episode, we’ll write your first Dockerfile — the recipe that creates your own custom container. Simple, step-by-step, with a real app. Let’s cook! 👨🍳🍱"
🍳 What is a Dockerfile?
A Dockerfile is like a recipe card for Docker. It tells Docker exactly how to build an image from scratch.
Just like:
- A cake recipe includes ingredients and steps
- A Dockerfile includes base image, dependencies, code, and commands
Once Docker reads the Dockerfile, it builds a Docker image, which you can then run as a container.
👨💻 Let's Build Your First Dockerfile
We’ll dockerize a basic Node.js app.
📁 Project Structure:
my-node-app/
├── Dockerfile
├── package.json
└── index.js
🧠 index.js (your app):
const http = require('http');
const server = http.createServer((req, res) => {
res.end('Hello from Docker!');
});
server.listen(3000, () => console.log('Server running on port 3000'));
📦 package.json:
{
"name": "my-node-app",
"version": "1.0.0",
"main": "index.js",
"scripts": {
"start": "node index.js"
}
}
🛠️ Writing the Dockerfile
Now create a file called Dockerfile (no extension!) and add this:
# Base image
FROM node:18
# Working directory
WORKDIR /app
# Copy files
COPY package*.json ./
# Install dependencies
RUN npm install
# Copy app source
COPY . .
# Expose port
EXPOSE 3000
# Start the app
CMD ["npm", "start"]
🧪 Build & Run the Docker Image
🔨 Build the image:
docker build -t my-node-app .
🚀 Run the container:
docker run -d -p 3000:3000 my-node-app
🌐 Open your browser:
Visit http://localhost:3000 — you’ll see: Hello from Docker!
🧠 What Did We Just Do?
-
FROM: Sets the base environment (Node.js) -
WORKDIR: The folder where your code lives inside the container -
COPY: Moves your code into the container -
RUN: Installs dependencies -
EXPOSE: Lets Docker know what port the app uses -
CMD: Tells Docker how to start the app
🛡️ Bonus Tips
- Use
.dockerignoreto skipnode_modules,logs, etc. - Always pin your base image (
node:18not justnode) - Keep Dockerfiles short, clean, and readable
🎯 Up Next: Docker CLI Mastery
In Episode 5, we’ll explore:
- Most used Docker commands
- How to manage images and containers
- Tricks to make your Docker life easier
💬 Let’s Build Together
Have you written your first Dockerfile? Did it work? Run into any errors?
Comment below — I’m here to help every beginner succeed 🚀
❤️ If you learned something new today, show some love with a like or drop a comment. Share this episode with your Dev.to fam!
🎬 Next: “Docker CLI Cheat Sheet — 15 Commands You’ll Actually Use”
This content originally appeared on DEV Community and was authored by Yash Sonawane
Yash Sonawane | Sciencx (2025-08-26T01:39:00+00:00) 🛳️ Docker Series: Episode 4 — Dockerfile for Beginners: Build Your Own Container Image. Retrieved from https://www.scien.cx/2025/08/26/%f0%9f%9b%b3%ef%b8%8f-docker-series-episode-4-dockerfile-for-beginners-build-your-own-container-image/
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