Docker Multi-Stage Distroless Builds & Image Hardening Skill

Shrink container images by 80% and eliminate OS-level CVEs using multi-stage BuildKit Dockerfiles, non-root distroless runtime images, and Trivy vulnerabil

---
name: docker-multistage
description: Shrink container images by 80% and eliminate OS-level CVEs using multi-stage BuildKit Dockerfiles, non-root distroless runtime images, and Trivy vulnerability scans. Use when working with Docker BuildKit, Distroless, Container Security, Trivy.
triggers:
  - docker multistage
  - docker buildkit
  - distroless
---

# Docker Multi-Stage Distroless Builds & Image Hardening Skill

## 1. When to Use This Skill
Load `skill-docker-multistage` whenever an engineering or operations task involves **Docker BuildKit, Distroless, Container Security, Trivy**. Specifically:
- Shrink container images by 80% and eliminate OS-level CVEs using multi-stage BuildKit Dockerfiles, non-root distroless runtime images, and Trivy vulnerability scans.
- Designing, reviewing, or debugging production configurations without guesswork or deprecated flags.
- Running deterministic pre-flight and post-execution verification checks before reporting completion.

## 2. Prerequisites & Required Environment
- **Target Stack:** Docker BuildKit, Distroless, Container Security, Trivy
- **Permissions:** Read-only inspection by default; ask for explicit confirmation before executing destructive mutations or production deployments.
- **Reference Repository:** `https://docs.docker.com/build/building/multi-stage/`

## 3. Step-by-Step Execution Playbook
1. **Context & Configuration Discovery:**
   Inspect existing project manifests (`package.json`, `wrangler.jsonc`, schema files, or environment declarations) before proposing changes. Never overwrite existing bindings or credentials blindly.
2. **Deterministic Implementation:**
   Apply the canonical patterns for **Docker BuildKit**:
   - Enforce strict schema/type validation at every external boundary.
   - Include explicit error handling, structured logging, and idempotency keys on all mutating calls.
   - Keep secrets in environment variables or secret stores—never hardcode tokens in source files.
3. **Verification & Regression Gate:**
   Run the verification commands below and inspect both exit codes and output payloads before marking the task complete.

## 4. Reference Commands & CLI Workflow
```bash
docker buildx build --target runtime -t app:latest .
trivy image app:latest
```

## 5. Edge Cases & Anti-Hallucination Guardrails
- **Zero Unverified Claims:** Never claim a deployment, migration, or API call succeeded without inspecting the command output or HTTP status code.
- **Rollback Readiness:** Always record the previous state or migration version so changes can be reverted cleanly if downstream health checks fail.

Synthesized Engineering Blueprint & Setup Guide