dockerfile-generator

What this skill does

# Dockerfile Generator

Generates production-ready Dockerfiles with multi-stage builds, optimized layer caching, and security best practices.

## When to Use

- "Create a Dockerfile"
- "Dockerize my application"
- "Container this app"
- "Setup Docker"
- "Optimize Dockerfile"

## Instructions

### 1. Detect Project Type

Scan for language/framework indicators:

```bash
# Node.js
[ -f "package.json" ] && echo "Node.js/JavaScript"

# Python
[ -f "requirements.txt" ] || [ -f "Pipfile" ] || [ -f "pyproject.toml" ] && echo "Python"

# Go
[ -f "go.mod" ] && echo "Go"

# Java
[ -f "pom.xml" ] || [ -f "build.gradle" ] && echo "Java"

# Ruby
[ -f "Gemfile" ] && echo "Ruby"

# PHP
[ -f "composer.json" ] && echo "PHP"

# Rust
[ -f "Cargo.toml" ] && echo "Rust"

# .NET
[ -f "*.csproj" ] && echo ".NET"
```

Read package files to determine framework (Express, Next.js, Django, Flask, etc.).

### 2. Generate Dockerfile by Language

## Node.js / JavaScript

**Basic Node.js:**
```dockerfile
# Multi-stage build for production
FROM node:20-alpine AS base

# Install dependencies only when needed
FROM base AS deps
WORKDIR /app

# Copy package files
COPY package.json package-lock.json* ./

# Install dependencies
RUN npm ci --only=production

# Development dependencies (for build)
FROM base AS build-deps
WORKDIR /app
COPY package.json package-lock.json* ./
RUN npm ci

# Build stage
FROM build-deps AS build
WORKDIR /app
COPY . .
RUN npm run build

# Production stage
FROM base AS runner
WORKDIR /app

# Don't run as root
RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 nodejs

# Copy built app
COPY --from=deps --chown=nodejs:nodejs /app/node_modules ./node_modules
COPY --from=build --chown=nodejs:nodejs /app/dist ./dist
COPY --chown=nodejs:nodejs package.json ./

USER nodejs

EXPOSE 3000

ENV NODE_ENV=production
ENV PORT=3000

CMD ["node", "dist/index.js"]
```

**Next.js:**
```dockerfile
FROM node:20-alpine AS base

# Dependencies
FROM base AS deps
RUN apk add --no-cache libc6-compat
WORKDIR /app

COPY package.json package-lock.json* ./
RUN npm ci

# Builder
FROM base AS builder
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .

# Disable telemetry
ENV NEXT_TELEMETRY_DISABLED 1

RUN npm run build

# Production
FROM base AS runner
WORKDIR /app

ENV NODE_ENV production
ENV NEXT_TELEMETRY_DISABLED 1

RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 nextjs

COPY --from=builder /app/public ./public
COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static

USER nextjs

EXPOSE 3000

ENV PORT 3000

CMD ["node", "server.js"]
```

## Python

**Flask:**
```dockerfile
FROM python:3.11-slim AS base

# Set environment variables
ENV PYTHONUNBUFFERED=1 \
    PYTHONDONTWRITEBYTECODE=1 \
    PIP_NO_CACHE_DIR=1 \
    PIP_DISABLE_PIP_VERSION_CHECK=1

WORKDIR /app

# Install system dependencies
RUN apt-get update && apt-get install -y \
    build-essential \
    && rm -rf /var/lib/apt/lists/*

# Dependencies
FROM base AS deps
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Production
FROM base AS runner

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

# Copy dependencies from deps stage
COPY --from=deps /usr/local/lib/python3.11/site-packages /usr/local/lib/python3.11/site-packages

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

USER appuser

EXPOSE 5000

CMD ["gunicorn", "--bind", "0.0.0.0:5000", "--workers", "4", "app:app"]
```

**Django:**
```dockerfile
FROM python:3.11-slim AS base

ENV PYTHONUNBUFFERED=1 \
    PYTHONDONTWRITEBYTECODE=1 \
    PIP_NO_CACHE_DIR=1

WORKDIR /app

# Dependencies
FROM base AS deps
RUN apt-get update && apt-get install -y \
    postgresql-client \
    && rm -rf /var/lib/apt/lists/*

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

# Production
FROM base AS runner

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

# Copy dependencies
COPY --from=deps /usr/local/lib/python3.11/site-packages /usr/local/lib/python3.11/site-packages
COPY --from=deps /usr/bin/pg_* /usr/bin/

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

# Collect static files
RUN python manage.py collectstatic --noinput

USER django

EXPOSE 8000

CMD ["gunicorn", "--bind", "0.0.0.0:8000", "--workers", "4", "myproject.wsgi:application"]
```

## Go

**Go application:**
```dockerfile
# Build stage
FROM golang:1.21-alpine AS builder

WORKDIR /app

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

# Copy source
COPY . .

# Build binary
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -ldflags="-w -s" -o main .

# Production stage (minimal image)
FROM scratch

# Copy CA certificates for HTTPS
COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/

# Copy binary from builder
COPY --from=builder /app/main /main

# Expose port
EXPOSE 8080

# Run binary
CMD ["/main"]
```

**With CGO (needs libc):**
```dockerfile
FROM golang:1.21-alpine AS builder

RUN apk add --no-cache gcc musl-dev

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

COPY . .
RUN go build -o main .

# Production
FROM alpine:latest

RUN apk --no-cache add ca-certificates
WORKDIR /root/

COPY --from=builder /app/main .

EXPOSE 8080

CMD ["./main"]
```

## Java

**Spring Boot (Gradle):**
```dockerfile
# Build stage
FROM gradle:8-jdk17 AS build

WORKDIR /app

# Copy gradle files
COPY build.gradle settings.gradle ./
COPY gradle ./gradle

# Download dependencies (cached layer)
RUN gradle dependencies --no-daemon

# Copy source and build
COPY src ./src
RUN gradle build --no-daemon -x test

# Production stage
FROM eclipse-temurin:17-jre-alpine

WORKDIR /app

# Create non-root user
RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring

# Copy jar from build stage
COPY --from=build /app/build/libs/*.jar app.jar

EXPOSE 8080

ENTRYPOINT ["java", "-jar", "app.jar"]
```

**Spring Boot (Maven):**
```dockerfile
FROM maven:3.9-eclipse-temurin-17 AS build

WORKDIR /app

# Copy pom and download dependencies (cached)
COPY pom.xml .
RUN mvn dependency:go-offline

# Copy source and build
COPY src ./src
RUN mvn package -DskipTests

# Production
FROM eclipse-temurin:17-jre-alpine

RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring

WORKDIR /app

COPY --from=build /app/target/*.jar app.jar

EXPOSE 8080

ENTRYPOINT ["java", "-jar", "app.jar"]
```

## Ruby

**Rails:**
```dockerfile
FROM ruby:3.2-alpine AS base

# Install system dependencies
RUN apk add --no-cache \
    build-base \
    postgresql-dev \
    nodejs \
    yarn \
    tzdata

WORKDIR /app

# Dependencies
FROM base AS deps

COPY Gemfile Gemfile.lock ./
RUN bundle install --jobs 4 --retry 3

# Production
FROM base AS runner

# Copy dependencies
COPY --from=deps /usr/local/bundle /usr/local/bundle

# Copy application
COPY . .

# Precompile assets
RUN bundle exec rake assets:precompile

# Create non-root user
RUN adduser -D rails
USER rails

EXPOSE 3000

CMD ["bundle", "exec", "rails", "server", "-b", "0.0.0.0"]
```

## Rust

**Rust application:**
```dockerfile
# Build stage
FROM rust:1.75-alpine AS builder

RUN apk add --no-cache musl-dev

WORKDIR /app

# Copy manifests
COPY Cargo.toml Cargo.lock ./

# Cache dependencies
RUN mkdir src && \
    echo "fn main() {}" > src/main.rs && \
    cargo build --release && \
    rm -rf src

# Copy source and build
COPY src ./src
RUN touch src/main.rs && cargo build --release

# Production (minimal)
FROM alpine:latest

RUN apk --no-cache add ca-certificates

WORKDIR /root/

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

EXPOSE 8080

CMD ["app"]
```

## PHP

**Laravel:**
```dockerfile
FROM php:8.2-fpm-alpine AS base

# Install system dependencies
RUN apk add --no-cache \
    postgresql-dev \
    zip \
    unzip

# Install PHP extensions
RUN docker-php-ext-install pdo pdo_pgsql

# Install composer
COPY --from=composer:latest /usr/bin/composer /usr/bin