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multi-stage-dockerfile

✓ Official★ 36,202

by github · part of github/awesome-copilot

Create optimized multi-stage Dockerfiles for any language or framework

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🧩 One of 7 skills in the github/awesome-copilot package — works on its own, and pairs well with its siblings.

This is the playbook your agent receives when the skill activates — you don't need to read it to use the skill, but it's here to audit before installing.

Your goal is to help me create efficient multi-stage Dockerfiles that follow best practices, resulting in smaller, more secure container images.

Multi-Stage Structure

  • Use a builder stage for compilation, dependency installation, and other build-time operations
  • Use a separate runtime stage that only includes what's needed to run the application
  • Copy only the necessary artifacts from the builder stage to the runtime stage
  • Use meaningful stage names with the AS keyword (e.g., FROM node:18 AS builder)
  • Place stages in logical order: dependencies → build → test → runtime

Base Images

  • Start with official, minimal base images when possible
  • Specify exact version tags to ensure reproducible builds (e.g., python:3.11-slim not just python)
  • Consider distroless images for runtime stages where appropriate
  • Use Alpine-based images for smaller footprints when compatible with your application
  • Ensure the runtime image has the minimal necessary dependencies

Layer Optimization

  • Organize commands to maximize layer caching
  • Place commands that change frequently (like code changes) after commands that change less frequently (like dependency installation)
  • Use .dockerignore to prevent unnecessary files from being included in the build context
  • Combine related RUN commands with && to reduce layer count
  • Consider using COPY --chown to set permissions in one step

Security Practices

  • Avoid running containers as root - use USER instruction to specify a non-root user
  • Remove build tools and unnecessary packages from the final image
  • Scan the final image for vulnerabilities
  • Set restrictive file permissions
  • Use multi-stage builds to avoid including build secrets in the final image

Performance Considerations

  • Use build arguments for configuration that might change between environments
  • Leverage build cache efficiently by ordering layers from least to most frequently changing
  • Consider parallelization in build steps when possible
  • Set appropriate environment variables like NODE_ENV=production to optimize runtime behavior
  • Use appropriate healthchecks for the application type with the HEALTHCHECK instruction