Stop 18 · DeploymentTopics · 5/9

Docker basics

In short

"It works on my laptop" stops being an excuse with Docker. You pack your app with everything it needs, and it runs the same way on any machine that has Docker.

A containerization tool that packages an app with all its dependencies into a portable, consistent 'container' that runs the same everywhere.

The jaadu gives a thumbs up as a crane loads a violet shipping container onto a ship.

Think of it like this

Shipping containers at the port

Before standard containers, every ship was loaded by hand, item by item. Now any crane, truck or ship handles the same box without caring what's inside. A Docker container is that box for your app.

Watch it happen

Dockerfile to running container

Dockerfile

Build stage

Copy dist

Image

Container

1/5docker build -t my-app . reads your Dockerfile from top to bottom.

The big ideas

What you need to know

Dockerfile is the recipe

A text file with step-by-step instructions: which base system, which files to copy, which commands to run.

Image vs container

An image is the packed result of the recipe. A container is a running copy of that image.

Layers get cached

Each instruction makes a layer. If package.json didn't change, Docker reuses the install layer and builds faster.

Multi-stage builds

Build with Node in one stage, then copy only the output into a small web server image.

See it in code

Walk through the code

dockerfile

1# Stage 1: build the app with Node2FROM node:22-alpine AS build3WORKDIR /app4COPY package*.json ./5RUN npm ci6COPY . .7RUN npm run build8 9# Stage 2: serve the static files with nginx10FROM nginx:alpine11COPY --from=build /app/dist /usr/share/nginx/html12EXPOSE 80

1/4Start from a small Node image and work inside /app.

Build it with docker build -t my-app . and run it with docker run -p 8080:80 my-app, then open localhost:8080. The final image has no Node or node_modules in it.

Save yourself the pain

Common mistakes

Oops

Copying the whole project before running npm ci.

Do this instead

Copy package files first, install, then copy the rest. Code changes then won't redo the slow install step.

Oops

Skipping a .dockerignore file.

Do this instead

Add node_modules, .git and .env to .dockerignore so they don't bloat the image or leak secrets.

Your mission

Containerise a Vite app

~30 min

Quick check

Why does the Dockerfile copy package*.json and run npm ci before copying the rest of the code?

Go deeper

1Write a simple `Dockerfile` for a small Node.js/Next.js app.
2Build and run the container locally with `docker build` and `docker run`.
3Learn why containers solve the classic 'works on my machine' problem.