autojanet/skills/understand/languages/dockerfile.md

Dockerfile Language Prompt Snippet

Key Concepts

• Multi-Stage Builds: Multiple FROM statements to separate build and runtime stages, reducing image size
• Layer Caching: Each instruction creates a layer; order instructions from least to most frequently changing for cache efficiency
• Base Images: FROM image:tag selects the starting image; prefer slim/alpine variants for smaller images
• COPY vs ADD: COPY for local files (preferred), ADD for URLs and tar extraction
• Build Arguments: ARG for build-time variables, ENV for runtime environment variables
• Health Checks: HEALTHCHECK instruction for container orchestrator readiness probes
• Entry Point vs CMD: ENTRYPOINT sets the executable, CMD provides default arguments
• User Permissions: USER instruction to run as non-root for security
• Ignore Patterns: .dockerignore excludes files from the build context (like .gitignore)

Notable File Patterns

• Dockerfile — Primary container image definition (at project root)
• Dockerfile.dev / Dockerfile.prod — Environment-specific Dockerfiles
• docker-compose.yml — Multi-container application orchestration
• docker-compose.override.yml — Local development overrides
• .dockerignore — Build context exclusion patterns

Edge Patterns

• Dockerfile deploys the application entry point it packages (COPY/CMD target)
• docker-compose depends_on Dockerfile(s) it references for building
• Dockerfile depends_on package manifests (package.json, requirements.txt) it copies for dependency installation
• docker-compose services create related edges between co-deployed components

Summary Style

"Multi-stage Docker build producing a minimal Node.js production image with N build stages." "Docker Compose configuration orchestrating N services with shared networking and persistent volumes." "Development Dockerfile with hot-reload support and mounted source volumes."