What is Docker?

Docker packages your app and all its dependencies into a container — a lightweight, portable environment that runs the same everywhere.

No more "it works on my machine."

Core Concepts

• Image: A blueprint for your container (like a class)
• Container: A running instance of an image (like an object)
• Dockerfile: Instructions to build an image
• Volume: Persistent storage for containers
• docker-compose: Run multiple containers together

Your First Dockerfile

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 3000
CMD ["npm", "start"]

Running It

docker build -t my-app .
docker run -p 3000:3000 my-app

That's it. Your app is containerized. Visit localhost:3000.

Why Students Should Care

• Deploy projects easily for demos
• No "install X, Y, Z" for teammates
• Learn a skill every company wants