AgentSkillsCN

docker

Dockerfile的最佳实践、安全加固、多阶段构建与镜像优化

SKILL.md
--- frontmatter
name: docker
description: Dockerfile best practices, security hardening, multi-stage builds, and image optimization

Docker Code Review Rules

Security (Critical)

  • •Run as non-root user (USER directive)
  • •Don't store secrets in image (use runtime injection)
  • •Don't use --privileged without justification
  • •Scan images for vulnerabilities
  • •Set readonly root filesystem where possible
  • •Review any use of build-time variables (e.g., ARG, ENV, LABEL values) that can be influenced by external inputs (such as --build-arg values or CI/CD environment variables sourced from untrusted users) to ensure they are not used in a way that enables build-time injection
  • •Never use HTML comments (<!-- -->) in Dockerfiles

Base Images

  • •Pin base image to specific version (not latest)
  • •Use official images from trusted sources
  • •Prefer minimal images (alpine, slim, distroless)
  • •Regularly update base images for security patches

Build Optimization

  • •Use multi-stage builds to reduce final image size
  • •Order instructions by change frequency (cache optimization)
  • •Combine RUN commands to reduce layers
  • •Use .dockerignore to exclude unnecessary files, sensitive data, and build artifacts like node_modules

Instructions (Essential)

  • •Use COPY instead of ADD (unless extracting archives)
  • •Set WORKDIR before COPY/RUN
  • •Use explicit EXPOSE for documentation
  • •Set meaningful LABEL metadata

Additional Instructions

  • •Explicitly set SHELL if bash/sh features are needed
  • •Set environment variables with ENV for configuration (not secrets)
  • •Clean up package manager caches after install (e.g., apt-get clean)
  • •Understand ENTRYPOINT vs CMD: use ENTRYPOINT for main command, CMD for default args
  • •Document container usage with OCI labels (org.opencontainers.image.*)

Health Checks

  • •Include HEALTHCHECK instruction
  • •Health check should verify app is actually working
  • •Set appropriate interval and timeout

Example Good Dockerfile Pattern

dockerfile
# Build stage
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production

# Runtime stage
FROM node:20-alpine

# Add OCI labels for documentation
LABEL org.opencontainers.image.title="My App"
LABEL org.opencontainers.image.description="Production web application"
LABEL org.opencontainers.image.version="1.0.0"

RUN addgroup -S appgroup && adduser -S appuser -G appgroup
WORKDIR /app

# Copy dependencies and app files
COPY --from=builder /app/node_modules ./node_modules
COPY . .

# Set environment variables (not secrets)
ENV NODE_ENV=production

USER appuser
EXPOSE 3000
HEALTHCHECK CMD wget -q --spider http://localhost:3000/health || exit 1

# Use ENTRYPOINT for main command, CMD for default args
ENTRYPOINT ["node"]
CMD ["server.js"]