Docker Multi-Stage Builds

Docker Multi-Stage Builds¶

Multi-stage build: build tools in the first stage, result in the final one. Dramatically smaller images.

Node.js¶

FROM node:18 AS builder WORKDIR /app COPY package*.json ./ RUN npm ci COPY . . RUN npm run build FROM nginx:alpine COPY –from=builder /app/dist /usr/share/nginx/html

40 MB instead of 1.2 GB¶

Go¶

FROM golang:1.22 AS builder WORKDIR /app COPY . . RUN CGO_ENABLED=0 go build -o server . FROM scratch COPY –from=builder /app/server /server ENTRYPOINT [“/server”]

15 MB¶

Python¶

FROM python:3.12 AS builder COPY requirements.txt . RUN pip install –user –no-cache-dir -r requirements.txt FROM python:3.12-slim COPY –from=builder /root/.local /root/.local COPY . . CMD [“python”, “app.py”]

• Name your stages (AS builder)
• Dependency files first -> better cache
• alpine/slim/scratch base
• Use .dockerignore

Smaller = Better¶

Multi-stage = smaller image, smaller attack surface, faster pull.