Mastering Docker Multi-Stage Builds

Docker multi-stage builds are a game-changer for creating lean, production-ready container images.

The Problem

Traditional Dockerfiles often result in bloated images: - Build tools included in final image - Source code present - Unnecessary dependencies - Large image sizes

The Solution: Multi-Stage Builds

# Build stage
FROM node:16 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

# Production stage
FROM node:16-alpine
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY package*.json ./
RUN npm install --production
CMD ["node", "dist/index.js"]

Benefits

  1. Smaller images: 90% size reduction possible
  2. Better security: Fewer attack surfaces
  3. Faster deployments: Less data to transfer
  4. Cleaner separation: Build vs runtime

Advanced Patterns

Using Multiple Builders

FROM golang:1.19 AS go-builder
# Go build steps...

FROM node:16 AS node-builder
# Node build steps...

FROM alpine:latest
COPY --from=go-builder /app/binary ./
COPY --from=node-builder /app/dist ./static

Best Practices

  • Order layers by change frequency
  • Use .dockerignore
  • Combine RUN commands
  • Use specific tags, not latest
  • Leverage build cache

Multi-stage builds are essential for modern Docker workflows!