Dockerfile Generator

Dockerfile Generator

Generate optimized, production-ready Dockerfiles for common application stacks with built-in best practices.

When to Use

• Creating new application containers
• Optimizing existing Dockerfiles
• Multi-stage builds for size reduction
• Language-specific containerization
• Security hardening
• Build performance optimization
• Implementing health checks

Universal Principles

Base Image Selection

Rule of thumb: Use Alpine for production (smaller, faster), Debian/Ubuntu for development (more tools).

Node.js/TypeScript

Multi-Stage Production Build

# Build stage
FROM node:20-alpine AS builder
WORKDIR /app

# Copy dependency files
COPY package*.json ./

# Install dependencies (including dev)
RUN npm ci

# Copy source
COPY . .

# Build/compile
RUN npm run build

# Lint and test (optional)
RUN npm run lint && npm run test:unit

# Production stage
FROM node:20-alpine
WORKDIR /app

# Create non-root user
RUN addgroup -g 1001 -S nodejs && adduser -S nodejs -u 1001

# Copy built artifacts from builder
COPY --from=builder --chown=nodejs:nodejs /app/dist ./dist
COPY --from=builder --chown=nodejs:nodejs /app/node_modules ./node_modules
COPY --chown=nodejs:nodejs package*.json ./

# Switch to non-root user
USER nodejs

# Health check
HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
  CMD node -e "require('http').get('http://localhost:3000/health', (r) => {if(r.statusCode!==200) throw new Error(r.statusCode)})"

EXPOSE 3000

CMD ["node", "dist/server.js"]

Development Container

FROM node:20-alpine

WORKDIR /app

RUN npm install -g nodemon

COPY package*.json ./
RUN npm ci

COPY . .

EXPOSE 3000

CMD ["nodemon", "src/server.js"]

Python

Multi-Stage Build

# Build stage
FROM python:3.11-slim AS builder
WORKDIR /app

# Install build dependencies
RUN apt-get update && apt-get install -y --no-install-recommends \
    build-essential && rm -rf /var/lib/apt/lists/*

# Create virtual environment
RUN python -m venv /opt/venv
ENV PATH="/opt/venv/bin:$PATH"

# Copy requirements
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Production stage
FROM python:3.11-slim
WORKDIR /app

# Create non-root user
RUN useradd -m -u 1001 appuser

# Copy virtual environment
COPY --from=builder /opt/venv /opt/venv
ENV PATH="/opt/venv/bin:$PATH"

# Copy application
COPY --chown=appuser:appuser . .

USER appuser

HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
  CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/health')"

EXPOSE 8000

CMD ["gunicorn", "-w", "4", "-b", "0.0.0.0:8000", "app:app"]

Go

Minimal Binary Container

# Build stage
FROM golang:1.21-alpine AS builder
WORKDIR /app

# Install build tools
RUN apk add --no-cache git

# Copy source
COPY go.mod go.sum ./
RUN go mod download

COPY . .

# Build static binary
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build \
    -ldflags="-w -s" \
    -o myapp .

# Production stage (minimal distroless)
FROM gcr.io/distroless/base-debian11

WORKDIR /app

# Copy binary
COPY --from=builder /app/myapp .

EXPOSE 8080

ENTRYPOINT ["./myapp"]

Standard Go Container

# Build stage
FROM golang:1.21-alpine AS builder
WORKDIR /app

COPY go.mod go.sum ./
RUN go mod download

COPY . .

RUN CGO_ENABLED=0 GOOS=linux go build -o app .

# Runtime stage
FROM alpine:3.18
RUN apk add --no-cache ca-certificates
WORKDIR /root/

COPY --from=builder /app/app .

EXPOSE 8080

CMD ["./app"]

Rust

Release Build

# Build stage
FROM rust:latest AS builder
WORKDIR /app

COPY . .

RUN cargo build --release

# Runtime stage
FROM debian:bookworm-slim
RUN apt-get update && apt-get install -y ca-certificates && rm -rf /var/lib/apt/lists/*

COPY --from=builder /app/target/release/myapp /usr/local/bin/

EXPOSE 8080

CMD ["myapp"]

Java

Spring Boot Application

# Build stage
FROM maven:3.9-eclipse-temurin-21 AS builder
WORKDIR /app

COPY pom.xml .
RUN mvn dependency:go-offline

COPY src ./src
RUN mvn package -DskipTests

# Runtime stage
FROM eclipse-temurin:21-jre-alpine
WORKDIR /app

# Create non-root user
RUN addgroup -g 1001 -S appgroup && adduser -S appuser -u 1001 -G appgroup

# Copy JAR
COPY --from=builder /app/target/app.jar .

USER appuser

HEALTHCHECK --interval=30s --timeout=5s --retries=3 \
  CMD wget --quiet --tries=1 --spider http://localhost:8080/actuator/health || exit 1

EXPOSE 8080

CMD ["java", "-jar", "app.jar"]

Key Optimization Techniques

Layer Caching

# BAD - changes frequently, invalidates cache
COPY . .
RUN npm ci
RUN npm run build

# GOOD - stable layers cached longer
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

.dockerignore

node_modules/
npm-debug.log
.git/
.gitignore
.env*
.vscode/
dist/
build/
coverage/
.DS_Store

Combine RUN Commands

# BAD - 3 layers
RUN apt-get update
RUN apt-get install -y curl
RUN rm -rf /var/lib/apt/lists/*

# GOOD - 1 layer
RUN apt-get update && apt-get install -y curl && rm -rf /var/lib/apt/lists/*

Security Patterns

Non-Root User

RUN groupadd -r appgroup && useradd -r -g appgroup appuser
USER appuser

Read-Only Filesystem

docker run --read-only -v /tmp:/tmp myapp:latest

Drop Capabilities

# Dockerfile
USER nobody:nobody

# Or runtime
docker run --cap-drop=ALL --cap-add=NET_BIND_SERVICE myapp:latest

Health Checks

HTTP Endpoint

HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
  CMD curl -f http://localhost:3000/health || exit 1

Custom Script

COPY healthcheck.sh .
RUN chmod +x healthcheck.sh
HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
  CMD ./healthcheck.sh

Database Connectivity

HEALTHCHECK --interval=30s --timeout=5s --retries=3 \
  CMD pg_isready -h localhost -U postgres || exit 1

Build Arguments

ARG NODE_ENV=production
ARG BUILD_DATE
ARG VCS_REF
ARG VERSION

LABEL org.opencontainers.image.created=$BUILD_DATE \
      org.opencontainers.image.revision=$VCS_REF \
      org.opencontainers.image.version=$VERSION

ENV NODE_ENV=$NODE_ENV

# Build
RUN npm run build:$NODE_ENV

Build Command

DOCKER_BUILDKIT=1 docker build \
  --build-arg NODE_ENV=production \
  --build-arg BUILD_DATE=$(date -u +'%Y-%m-%dT%H:%M:%SZ') \
  --build-arg VCS_REF=$(git rev-parse --short HEAD) \
  --build-arg VERSION=1.0.0 \
  -t myapp:1.0.0 \
  .

Common Issues & Solutions

Issue: Large Image Size

Solution: Use multi-stage builds, Alpine base images, and .dockerignore

# Before: 1.2GB
FROM ubuntu:22.04
RUN apt-get update && apt-get install -y python3 pip ...
COPY . .

# After: 120MB
FROM python:3.11-slim AS builder
RUN pip install --user ...
FROM python:3.11-slim
COPY --from=builder ...

Issue: Layer Cache Invalidation

Solution: Order commands by change frequency

# Stable → Frequently changing
COPY package.json .
RUN npm ci
COPY . .
RUN npm run build

Issue: Slow Builds

Solution: Enable BuildKit and use layer caching

# Enable BuildKit
export DOCKER_BUILDKIT=1

# Build with progress output
docker buildx build --progress=plain -t myapp .

Testing Dockerfile

# Build image
docker build -t myapp:test .

# Run with shell for inspection
docker run -it myapp:test /bin/sh

# Verify file contents
docker run myapp:test ls -la /app

# Check environment
docker run myapp:test env

References

• Official Dockerfile reference: https://docs.docker.com/engine/reference/builder/
• Best practices: https://docs.docker.com/develop/develop-images/dockerfile_best-practices/
• BuildKit: https://docs.docker.com/build/buildkit/