Docker Multi-Stage Builds Guide

# ❌ Single stage — 1.2 GB image
FROM node:22
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build
# Build tools, source code, devDependencies all in final image
CMD ["node", "dist/server.js"]

# ✅ Multi-stage — 180 MB image
# Stage 1: Build
FROM node:22 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# Stage 2: Production
FROM node:22-slim
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
COPY --from=builder /app/package.json ./
USER node
CMD ["node", "dist/server.js"]

FROM golang:1.22 AS builder
WORKDIR /app
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -o /server ./cmd/server

# Distroless — no shell, no package manager, no OS utilities
FROM gcr.io/distroless/static-debian12
COPY --from=builder /server /server
USER nonroot
ENTRYPOINT ["/server"]

FROM node:22-alpine AS deps
WORKDIR /app
COPY package*.json ./
RUN npm ci --omit=dev

FROM node:22-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM node:22-alpine
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/package.json ./
USER node
EXPOSE 3000
CMD ["node", "dist/server.js"]

FROM python:3.12 AS builder
WORKDIR /app
COPY requirements.txt .
RUN pip install --user --no-cache-dir -r requirements.txt

FROM python:3.12-slim
WORKDIR /app
COPY --from=builder /root/.local /root/.local
COPY . .
ENV PATH=/root/.local/bin:$PATH
USER nobody
CMD ["python", "app.py"]

FROM eclipse-temurin:21-jdk AS builder
WORKDIR /app
COPY . .
RUN ./gradlew bootJar --no-daemon

FROM eclipse-temurin:21-jre
WORKDIR /app
COPY --from=builder /app/build/libs/app.jar ./app.jar
USER 1000
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "app.jar"]

FROM node:22-alpine AS base
WORKDIR /app
COPY package*.json ./

FROM base AS deps
RUN npm ci --omit=dev

FROM base AS build
RUN npm ci
COPY . .
RUN npm run build

FROM base AS test
RUN npm ci
COPY . .
RUN npm test

FROM node:22-alpine AS production
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY --from=build /app/dist ./dist
USER node
CMD ["node", "dist/server.js"]

# Only run tests
docker build --target test .

# Build production image
docker build --target production -t my-app:latest .

FROM nginx:alpine

# Copy from another image (not a build stage)
COPY --from=caddy:latest /usr/bin/caddy /usr/local/bin/caddy

# Copy from a specific tag
COPY --from=busybox:latest /bin/wget /usr/local/bin/wget

node_modules
.git
.github
*.md
Dockerfile
docker-compose*.yml
.env*
coverage/
tests/