Container Debug

### Overall judgment High-quality, practical skill for Docker/Docker Compose debugging. It offers broad, deep coverage of real-world container issues with precise commands and clear patterns. Well-suited as a primary debugging reference for containerized applications. ### Strengths - Covers the full lifecycle: logs, exec, crashes, networking, resources, builds, health checks, and Compose orchestration. - Commands are concrete and immediately usable, with sensible defaults and examples. - Includes advanced but valuable techniques (nsenter, sidecar debug containers, netshoot, tcpdump). - Emphasizes key mental models (0.0.0.0 vs 127.0.0.1, user-defined networks for DNS, OOM exit codes, health check behavior). ### Risks / Limitations - Some commands are potentially destructive, e.g. `docker system prune -a --volumes` and aggressive cleanup; these must be recommended carefully and only after explicit confirmation and backup. - Assumes a fairly standard Docker environment, typically Linux; commands using cgroups paths, `nsenter`, or specific tools may not work as-is on all platforms (e.g., Windows, rootless Docker, minimal images). - Focused strictly on Docker/Compose; not applicable to Kubernetes or higher-level orchestrators. ### Recommended scenarios - Debugging dev or production Docker containers that crash, fail health checks, or behave differently from the host environment. - Investigating inter-service communication problems in Docker Compose (DNS, ports, startup ordering, health-based dependencies). - Analyzing resource-related failures (OOM kills, high memory/CPU usage, disk exhaustion or log growth) inside containers. - Debugging multi-stage Docker builds or unexpected final image contents using targeted builds and image inspection. - Using as a structured checklist/playbook when walking a user step-by-step through container troubleshooting.