Shrinking Images with Docker Multi-Stage Builds

Procedures / docker-multistage.html

Keep only build tools where needed so the final image stays small.

💬 Splitting build and run images keeps the final image light.

Procedure

• Install dependencies and compile in the build stage.
• Copy only the artifacts and runtime into the run stage.

Example Dockerfile

# stage 1: build
FROM node:20-alpine AS build
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# stage 2: run
FROM node:20-alpine
WORKDIR /app
ENV NODE_ENV=production
COPY --from=build /app/dist ./dist
COPY package*.json ./
RUN npm ci --omit=dev
CMD ["node", "dist/server.js"]

Build and check

docker build -t myapp .
docker images myapp        # compare sizes
docker run --rm -p 3000:3000 myapp

When it fails

• File not found: ensure the COPY --from=build path matches the build output.
• Missing .dockerignore: copying node_modules bloats the image and slows builds.

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