Dockerfile Instructions in Docker

From the Docker cheat sheet · Dockerfile · verified Jul 2026

The essential Dockerfile commands for building images

dockerfile

FROM node:22-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --production
COPY . .
ENV NODE_ENV=production
EXPOSE 3000
CMD ["node", "server.js"]

💡 Always use specific image tags (node:22-alpine) not "latest" — reproducible builds

⚡ Copy package.json first, then npm install, then copy source — maximizes Docker layer cache

📌 ARG is build-time only; ENV persists into the running container — know the difference

🟢 Run as a non-root USER in production — it only takes 2 lines and prevents privilege escalation

dockerfilebuildinstructions

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