create-multistage-dockerfile

name	create-multistage-dockerfile
description	Create multi-stage Dockerfiles that separate build and runtime environments for minimal production images. Covers builder/runtime stage separation, artifact copying, scratch/distroless/alpine targets, and size comparison. Use when production images are too large, when build tools are included in the final image, when you need separate dev and prod images from one Dockerfile, or when deploying to constrained environments like edge or serverless.
license	MIT
allowed-tools	Read Write Edit Bash Grep Glob
metadata	{"author":"Philipp Thoss","version":"1.0","domain":"containerization","complexity":"intermediate","language":"Docker","tags":"docker, multi-stage, distroless, alpine, scratch, optimization"}

Create Multi-Stage Dockerfile

Build multi-stage Dockerfiles that produce minimal production images by separating build tooling from runtime.

When to Use

• Production images are too large (>500MB for compiled languages)
• Build tools (compilers, dev headers) are included in the final image
• Need separate images for development and production from one Dockerfile
• Deploying to constrained environments (edge, serverless)

Inputs

• Required: Existing Dockerfile or project to containerize
• Required: Language and build system (npm, pip, go build, cargo, maven)
• Optional: Target runtime base (slim, alpine, distroless, scratch)
• Optional: Size budget for final image

Procedure

Step 1: Identify Build vs Runtime Dependencies

Category	Build Stage	Runtime Stage
Compilers	gcc, g++, rustc	Not needed
Package managers	npm, pip, cargo	Sometimes (interpreted langs)
Dev headers	-dev packages	Not needed
Source code	Full source tree	Only compiled output
Test frameworks	jest, pytest	Not needed

Step 2: Structure the Multi-Stage Build

The core pattern: build in a fat image, copy artifacts to a slim image.

# ---- Build Stage ----
FROM <build-image> AS builder
WORKDIR /src
COPY <dependency-manifest> .
RUN <install-dependencies>
COPY . .
RUN <build-command>

# ---- Runtime Stage ----
FROM <runtime-image>
COPY --from=builder /src/<artifact> /<dest>
EXPOSE <port>
CMD [<entrypoint>]

Step 3: Apply Language-Specific Patterns

Node.js (pruned node_modules)

FROM node:22-bookworm AS builder
WORKDIR /src
COPY package.json package-lock.json ./
RUN npm ci
COPY . .
RUN npm run build && npm prune --omit=dev

FROM node:22-bookworm-slim
RUN groupadd -r app && useradd -r -g app app
WORKDIR /app
COPY --from=builder /src/dist ./dist
COPY --from=builder /src/node_modules ./node_modules
COPY --from=builder /src/package.json .
USER app
EXPOSE 3000
CMD ["node", "dist/index.js"]

Python (virtualenv copy)

FROM python:3.12-bookworm AS builder
WORKDIR /src
RUN python -m venv /opt/venv
ENV PATH="/opt/venv/bin:$PATH"
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .

FROM python:3.12-slim-bookworm
COPY --from=builder /opt/venv /opt/venv
ENV PATH="/opt/venv/bin:$PATH"
WORKDIR /app
COPY --from=builder /src .
RUN groupadd -r app && useradd -r -g app app
USER app
EXPOSE 8000
CMD ["python", "app.py"]

Go (static binary to scratch)

FROM golang:1.23-bookworm AS builder
WORKDIR /src
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-s -w" -o /server ./cmd/server

FROM scratch
COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
COPY --from=builder /server /server
EXPOSE 8080
ENTRYPOINT ["/server"]

Rust (static musl binary)

FROM rust:1.82-bookworm AS builder
RUN apt-get update && apt-get install -y musl-tools && rm -rf /var/lib/apt/lists/*
RUN rustup target add x86_64-unknown-linux-musl
WORKDIR /src
COPY Cargo.toml Cargo.lock ./
RUN mkdir src && echo "fn main() {}" > src/main.rs \
    && cargo build --release --target x86_64-unknown-linux-musl \
    && rm -rf src
COPY . .
RUN touch src/main.rs && cargo build --release --target x86_64-unknown-linux-musl

FROM scratch
COPY --from=builder /src/target/x86_64-unknown-linux-musl/release/myapp /myapp
EXPOSE 8080
ENTRYPOINT ["/myapp"]

Expected: Final image contains only the runtime and compiled artifacts.

On failure: Check COPY --from=builder paths. Use docker build --target builder to debug the build stage.

Step 4: Choose Runtime Base

Base	Size	Shell	Use Case
scratch	0 MB	No	Static Go/Rust binaries
gcr.io/distroless/static	~2 MB	No	Static binaries + CA certs
gcr.io/distroless/base	~20 MB	No	Dynamic binaries (libc)
*-slim	50-150 MB	Yes	Interpreted languages
alpine	~7 MB	Yes	When shell access needed

Note: Alpine uses musl libc. Some Python wheels and Node native modules may not work. Prefer -slim (glibc) for interpreted languages.

Step 5: Build Args Across Stages

ARG APP_VERSION=0.0.0

FROM golang:1.23 AS builder
ARG APP_VERSION
RUN go build -ldflags="-X main.version=${APP_VERSION}" -o /server .

FROM gcr.io/distroless/static
COPY --from=builder /server /server
ENTRYPOINT ["/server"]

Build with: docker build --build-arg APP_VERSION=1.2.3 .

Note: ARG before FROM is global. Each stage must re-declare ARG to use it.

Step 6: Compare Image Sizes

# Build both variants
docker build -t myapp:fat --target builder .
docker build -t myapp:slim .

# Compare sizes
docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.Size}}" | grep myapp

Expected: Production image is 50-90% smaller than the build stage.

Validation

• docker build completes for all stages
• Final image does not contain build tools (compilers, dev headers)
• docker run works correctly from the slim image
• Image size is significantly reduced vs single-stage
• COPY --from=builder paths are correct
• No source code leaks into the production image

Common Pitfalls

• Missing runtime libraries: Compiled code may need shared libraries (libc, libssl). Test the slim image thoroughly.
• Broken COPY --from paths: The artifact path must match exactly. Use docker build --target builder then docker run --rm builder ls /path to debug.
• Alpine musl issues: Native Node.js addons and some Python packages fail on Alpine. Use -slim instead.
• Global ARG scope: An ARG declared before FROM is available to FROM lines only. Re-declare inside each stage that needs it.
• Forgetting CA certificates: scratch has no certificates. Copy /etc/ssl/certs/ca-certificates.crt from the builder or use distroless.

Related Skills

• create-dockerfile - single-stage general Dockerfiles
• create-r-dockerfile - R-specific Dockerfiles with rocker images
• optimize-docker-build-cache - layer caching and BuildKit features
• setup-compose-stack - compose configurations using multi-stage images