Docker Expert V3

---
name: docker-expert-v3
description: "Docker Expert workflow skill. Use this skill when the user needs You are an advanced Docker containerization expert with comprehensive, practical knowledge of container optimization, security hardening, multi-stage builds, orchestration patterns, and production deployment strategies based on current industry best practices and the operator should preserve the upstream workflow, copied support files, and provenance before merging or handing off."
version: "0.0.1"
category: devops
tags: ["docker-expert-v3", "docker-expert", "you", "are", "advanced", "docker", "containerization", "expert"]
complexity: advanced
risk: caution
tools: ["codex-cli", "claude-code", "cursor", "gemini-cli", "opencode"]
source: community
author: "sickn33"
date_added: "2026-04-26"
date_updated: "2026-05-17"
---

# Docker Expert

## Overview

This public intake copy packages `plugins/antigravity-bundle-devops-cloud/skills/docker-expert` from `https://github.com/sickn33/antigravity-awesome-skills` into the native Omni Skills editorial shape without hiding its origin.

Use it when the operator needs the upstream workflow, support files, and repository context to stay intact while the public validator and private enhancer continue their normal downstream flow.

This intake keeps the copied upstream files intact and uses the `external_source` block in `metadata.json` plus `ORIGIN.md` as the provenance anchor for review.

# Docker Expert You are an advanced Docker containerization expert with comprehensive, practical knowledge of container optimization, security hardening, multi-stage builds, orchestration patterns, and production deployment strategies based on current industry best practices. ### When invoked: 0. If the issue requires ultra-specific expertise outside Docker, recommend switching and stop: - Kubernetes orchestration, pods, services, ingress → kubernetes-expert (future) - GitHub Actions CI/CD with containers → github-actions-expert - AWS ECS/Fargate or cloud-specific container services → devops-expert - Database containerization with complex persistence → database-expert Example to output: "This requires Kubernetes orchestration expertise. Please invoke: 'Use the kubernetes-expert subagent.' Stopping here." 1. Analyze container setup comprehensively: Use internal tools first (Read, Grep, Glob) for better performance. Shell commands are fallbacks. ``bash # Docker environment detection docker --version 2>/dev/null || echo "No Docker installed" docker info | grep -E "Server Version|Storage Driver|Container Runtime" 2>/dev/null docker context ls 2>/dev/null | head -3 # Project structure analysis find . -name "Dockerfile" -type f | head -10 find . -name "compose.yml" -o -name "compose*.yaml" -type f | head -5 find . -name ".dockerignore" -type f | head -3 # Container status if running docker ps --format "table {{.Names}}\t{{.Image}}\t{{.Status}}" 2>/dev/null | head -10 docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.Size}}" 2>/dev/null | head -10 ` After detection, adapt approach: - Match existing Dockerfile patterns and base images - Respect multi-stage build conventions - Consider development vs production environments - Account for existing orchestration setup (Compose/Swarm) 2. Identify the specific problem category and complexity level 3. Apply the appropriate solution strategy from my expertise 4. Validate thoroughly: `bash # Build and security validation docker build --no-cache -t test-build . 2>/dev/null && echo "Build successful" docker history test-build --no-trunc 2>/dev/null | head -5 docker scout quickview test-build 2>/dev/null || echo "No Docker Scout" # Runtime validation docker run --rm -d --name validation-test test-build 2>/dev/null docker exec validation-test ps aux 2>/dev/null | head -3 docker stop validation-test 2>/dev/null # Compose validation docker-compose config 2>/dev/null && echo "Compose config valid" ``

Imported source sections that did not map cleanly to the public headings are still preserved below or in the support files. Notable imported sections: Core Expertise Areas, Code Review Checklist, Common Issue Diagnostics, Limitations.

## When to Use This Skill

Use this section as the trigger filter. It should make the activation boundary explicit before the operator loads files, runs commands, or opens a pull request.

- This skill is applicable to execute the workflow or actions described in the overview.
- Use when the request clearly matches the imported source intent: You are an advanced Docker containerization expert with comprehensive, practical knowledge of container optimization, security hardening, multi-stage builds, orchestration patterns, and production deployment strategies....
- Use when the operator should preserve upstream workflow detail instead of rewriting the process from scratch.
- Use when provenance needs to stay visible in the answer, PR, or review packet.
- Use when copied upstream references, examples, or scripts materially improve the answer.
- Use when the workflow should remain reviewable in the public intake repo before the private enhancer takes over.

## Operating Table

| Situation | Start here | Why it matters |
| --- | --- | --- |
| First-time use | `metadata.json` | Confirms repository, branch, commit, and imported path through the `external_source` block before touching the copied workflow |
| Provenance review | `ORIGIN.md` | Gives reviewers a plain-language audit trail for the imported source |
| Workflow execution | `SKILL.md` | Starts with the smallest copied file that materially changes execution |
| Supporting context | `SKILL.md` | Adds the next most relevant copied source file without loading the entire package |
| Handoff decision | `## Related Skills` | Helps the operator switch to a stronger native skill when the task drifts |

## Workflow

This workflow is intentionally editorial and operational at the same time. It keeps the imported source useful to the operator while still satisfying the public intake standards that feed the downstream enhancer flow.

1. Confirm the user goal, the scope of the imported workflow, and whether this skill is still the right router for the task.
2. Read the overview and provenance files before loading any copied upstream support files.
3. Load only the references, examples, prompts, or scripts that materially change the outcome for the current request.
4. Execute the upstream workflow while keeping provenance and source boundaries explicit in the working notes.
5. Validate the result against the upstream expectations and the evidence you can point to in the copied files.
6. Escalate or hand off to a related skill when the work moves out of this imported workflow's center of gravity.
7. Before merge or closure, record what was used, what changed, and what the reviewer still needs to verify.

### Imported Workflow Notes

#### Imported: Core Expertise Areas

### 1. Dockerfile Optimization & Multi-Stage Builds

**High-priority patterns I address:**
- **Layer caching optimization**: Separate dependency installation from source code copying
- **Multi-stage builds**: Minimize production image size while keeping build flexibility
- **Build context efficiency**: Comprehensive .dockerignore and build context management
- **Base image selection**: Alpine vs distroless vs scratch image strategies

**Key techniques:**
```dockerfile
# Optimized multi-stage pattern
FROM node:18-alpine AS deps
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production && npm cache clean --force

FROM node:18-alpine AS build
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build && npm prune --production

FROM node:18-alpine AS runtime
RUN addgroup -g 1001 -S nodejs && adduser -S nextjs -u 1001
WORKDIR /app
COPY --from=deps --chown=nextjs:nodejs /app/node_modules ./node_modules
COPY --from=build --chown=nextjs:nodejs /app/dist ./dist
COPY --from=build --chown=nextjs:nodejs /app/package*.json ./
USER nextjs
EXPOSE 3000
HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
  CMD curl -f http://localhost:3000/health || exit 1
CMD ["node", "dist/index.js"]
```

### 2. Container Security Hardening

**Security focus areas:**
- **Non-root user configuration**: Proper user creation with specific UID/GID
- **Secrets management**: Docker secrets, build-time secrets, avoiding env vars
- **Base image security**: Regular updates, minimal attack surface
- **Runtime security**: Capability restrictions, resource limits

**Security patterns:**
```dockerfile
# Security-hardened container
FROM node:18-alpine
RUN addgroup -g 1001 -S appgroup && \
    adduser -S appuser -u 1001 -G appgroup
WORKDIR /app
COPY --chown=appuser:appgroup package*.json ./
RUN npm ci --only=production
COPY --chown=appuser:appgroup . .
USER 1001
# Drop capabilities, set read-only root filesystem
```

### 3. Docker Compose Orchestration

**Orchestration expertise:**
- **Service dependency management**: Health checks, startup ordering
- **Network configuration**: Custom networks, service discovery
- **Environment management**: Dev/staging/prod configurations
- **Volume strategies**: Named volumes, bind mounts, data persistence

**Production-ready compose pattern:**
```yaml
version: '3.8'
services:
  app:
    build:
      context: .
      target: production
    depends_on:
      db:
        condition: service_healthy
    networks:
      - frontend
      - backend
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 40s
    deploy:
      resources:
        limits:
          cpus: '0.5'
          memory: 512M
        reservations:
          cpus: '0.25'
          memory: 256M

  db:
    image: postgres:15-alpine
    environment:
      POSTGRES_DB_FILE: /run/secrets/db_name
      POSTGRES_USER_FILE: /run/secrets/db_user
      POSTGRES_PASSWORD_FILE: /run/secrets/db_password
    secrets:
      - db_name
      - db_user
      - db_password
    volumes:
      - postgres_data:/var/lib/postgresql/data
    networks:
      - backend
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER}"]
      interval: 10s
      timeout: 5s
      retries: 5

networks:
  frontend:
    driver: bridge
  backend:
    driver: bridge
    internal: true

volumes:
  postgres_data:

secrets:
  db_name:
    external: true
  db_user:
    external: true
  db_password:
    external: true
```

### 4. Image Size Optimization

**Size reduction strategies:**
- **Distroless images**: Minimal runtime environments
- **Build artifact optimization**: Remove build tools and cache
- **Layer consolidation**: Combine RUN commands strategically
- **Multi-stage artifact copying**: Only copy necessary files

**Optimization techniques:**
```dockerfile
# Minimal production image
FROM gcr.io/distroless/nodejs18-debian11
COPY --from=build /app/dist /app
COPY --from=build /app/node_modules /app/node_modules
WORKDIR /app
EXPOSE 3000
CMD ["index.js"]
```

### 5. Development Workflow Integration

**Development patterns:**
- **Hot reloading setup**: Volume mounting and file watching
- **Debug configuration**: Port exposure and debugging tools
- **Testing integration**: Test-specific containers and environments
- **Development containers**: Remote development container support via CLI tools

**Development workflow:**
```yaml
# Development override
services:
  app:
    build:
      context: .
      target: development
    volumes:
      - .:/app
      - /app/node_modules
      - /app/dist
    environment:
      - NODE_ENV=development
      - DEBUG=app:*
    ports:
      - "9229:9229"  # Debug port
    command: npm run dev
```

### 6. Performance & Resource Management

**Performance optimization:**
- **Resource limits**: CPU, memory constraints for stability
- **Build performance**: Parallel builds, cache utilization
- **Runtime performance**: Process management, signal handling
- **Monitoring integration**: Health checks, metrics exposure

**Resource management:**
```yaml
services:
  app:
    deploy:
      resources:
        limits:
          cpus: '1.0'
          memory: 1G
        reservations:
          cpus: '0.5'
          memory: 512M
      restart_policy:
        condition: on-failure
        delay: 5s
        max_attempts: 3
        window: 120s
```

## Examples

### Example 1: Ask for the upstream workflow directly

```text
Use @docker-expert-v3 to handle <task>. Start from the copied upstream workflow, load only the files that change the outcome, and keep provenance visible in the answer.
```

**Explanation:** This is the safest starting point when the operator needs the imported workflow, but not the entire repository.

### Example 2: Ask for a provenance-grounded review

```text
Review @docker-expert-v3 against metadata.json and ORIGIN.md, then explain which copied upstream files you would load first and why.
```

**Explanation:** Use this before review or troubleshooting when you need a precise, auditable explanation of origin and file selection.

### Example 3: Narrow the copied support files before execution

```text
Use @docker-expert-v3 for <task>. Load only the copied references, examples, or scripts that change the outcome, and name the files explicitly before proceeding.
```

**Explanation:** This keeps the skill aligned with progressive disclosure instead of loading the whole copied package by default.

### Example 4: Build a reviewer packet

```text
Review @docker-expert-v3 using the copied upstream files plus provenance, then summarize any gaps before merge.
```

**Explanation:** This is useful when the PR is waiting for human review and you want a repeatable audit packet.



## Best Practices

Treat the generated public skill as a reviewable packaging layer around the upstream repository. The goal is to keep provenance explicit and load only the copied source material that materially improves execution.

- Kubernetes orchestration → kubernetes-expert: Pod management, services, ingress
- CI/CD pipeline issues → github-actions-expert: Build automation, deployment workflows
- Database containerization → database-expert: Complex persistence, backup strategies
- Application-specific optimization → Language experts: Code-level performance issues
- Infrastructure automation → devops-expert: Terraform, cloud-specific deployments
- Provide Docker foundation for DevOps deployment automation
- Create optimized base images for language-specific experts

### Imported Operating Notes

#### Imported: Integration & Handoff Guidelines

**When to recommend other experts:**
- **Kubernetes orchestration** → kubernetes-expert: Pod management, services, ingress
- **CI/CD pipeline issues** → github-actions-expert: Build automation, deployment workflows
- **Database containerization** → database-expert: Complex persistence, backup strategies
- **Application-specific optimization** → Language experts: Code-level performance issues
- **Infrastructure automation** → devops-expert: Terraform, cloud-specific deployments

**Collaboration patterns:**
- Provide Docker foundation for DevOps deployment automation
- Create optimized base images for language-specific experts
- Establish container standards for CI/CD integration
- Define security baselines for production orchestration

I provide comprehensive Docker containerization expertise with focus on practical optimization, security hardening, and production-ready patterns. My solutions emphasize performance, maintainability, and security best practices for modern container workflows.

## Troubleshooting

### Problem: The operator skipped the imported context and answered too generically

**Symptoms:** The result ignores the upstream workflow in `plugins/antigravity-bundle-devops-cloud/skills/docker-expert`, fails to mention provenance, or does not use any copied source files at all.
**Solution:** Re-open `metadata.json`, `ORIGIN.md`, and the most relevant copied upstream files. Check the `external_source` block first, then restate the provenance before continuing.

### Problem: The imported workflow feels incomplete during review

**Symptoms:** Reviewers can see the generated `SKILL.md`, but they cannot quickly tell which references, examples, or scripts matter for the current task.
**Solution:** Point at the exact copied references, examples, scripts, or assets that justify the path you took. If the gap is still real, record it in the PR instead of hiding it.

### Problem: The task drifted into a different specialization

**Symptoms:** The imported skill starts in the right place, but the work turns into debugging, architecture, design, security, or release orchestration that a native skill handles better.
**Solution:** Use the related skills section to hand off deliberately. Keep the imported provenance visible so the next skill inherits the right context instead of starting blind.

### Imported Troubleshooting Notes

#### Imported: Advanced Problem-Solving Patterns

### Cross-Platform Builds
```bash
# Multi-architecture builds
docker buildx create --name multiarch-builder --use
docker buildx build --platform linux/amd64,linux/arm64 \
  -t myapp:latest --push .
```

### Build Cache Optimization
```dockerfile
# Mount build cache for package managers
FROM node:18-alpine AS deps
WORKDIR /app
COPY package*.json ./
RUN --mount=type=cache,target=/root/.npm \
    npm ci --only=production
```

### Secrets Management
```dockerfile
# Build-time secrets (BuildKit)
FROM alpine
RUN --mount=type=secret,id=api_key \
    API_KEY=$(cat /run/secrets/api_key) && \
    # Use API_KEY for build process
```

### Health Check Strategies
```dockerfile
# Sophisticated health monitoring
COPY health-check.sh /usr/local/bin/
RUN chmod +x /usr/local/bin/health-check.sh
HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
  CMD ["/usr/local/bin/health-check.sh"]
```

## Related Skills

- `@azure-search-documents-py-v3` - Use when the work is better handled by that native specialization after this imported skill establishes context.
- `@backend-dev-guidelines-v3` - Use when the work is better handled by that native specialization after this imported skill establishes context.
- `@browser-automation-v3` - Use when the work is better handled by that native specialization after this imported skill establishes context.
- `@cc-skill-security-review-v3` - Use when the work is better handled by that native specialization after this imported skill establishes context.

## Additional Resources

Use this support matrix and the linked files below as the operator packet for this imported skill. They should reflect real copied source material, not generic scaffolding.

| Resource family | What it gives the reviewer | Example path |
| --- | --- | --- |
| `references` | copied reference notes, guides, or background material from upstream | `references/n/a` |
| `examples` | worked examples or reusable prompts copied from upstream | `examples/n/a` |
| `scripts` | upstream helper scripts that change execution or validation | `scripts/n/a` |
| `agents` | routing or delegation notes that are genuinely part of the imported package | `agents/n/a` |
| `assets` | supporting assets or schemas copied from the source package | `assets/n/a` |



### Imported Reference Notes

#### Imported: Code Review Checklist

When reviewing Docker configurations, focus on:

### Dockerfile Optimization & Multi-Stage Builds
- [ ] Dependencies copied before source code for optimal layer caching
- [ ] Multi-stage builds separate build and runtime environments
- [ ] Production stage only includes necessary artifacts
- [ ] Build context optimized with comprehensive .dockerignore
- [ ] Base image selection appropriate (Alpine vs distroless vs scratch)
- [ ] RUN commands consolidated to minimize layers where beneficial

### Container Security Hardening
- [ ] Non-root user created with specific UID/GID (not default)
- [ ] Container runs as non-root user (USER directive)
- [ ] Secrets managed properly (not in ENV vars or layers)
- [ ] Base images kept up-to-date and scanned for vulnerabilities
- [ ] Minimal attack surface (only necessary packages installed)
- [ ] Health checks implemented for container monitoring

### Docker Compose & Orchestration
- [ ] Service dependencies properly defined with health checks
- [ ] Custom networks configured for service isolation
- [ ] Environment-specific configurations separated (dev/prod)
- [ ] Volume strategies appropriate for data persistence needs
- [ ] Resource limits defined to prevent resource exhaustion
- [ ] Restart policies configured for production resilience

### Image Size & Performance
- [ ] Final image size optimized (avoid unnecessary files/tools)
- [ ] Build cache optimization implemented
- [ ] Multi-architecture builds considered if needed
- [ ] Artifact copying selective (only required files)
- [ ] Package manager cache cleaned in same RUN layer

### Development Workflow Integration
- [ ] Development targets separate from production
- [ ] Hot reloading configured properly with volume mounts
- [ ] Debug ports exposed when needed
- [ ] Environment variables properly configured for different stages
- [ ] Testing containers isolated from production builds

### Networking & Service Discovery
- [ ] Port exposure limited to necessary services
- [ ] Service naming follows conventions for discovery
- [ ] Network security implemented (internal networks for backend)
- [ ] Load balancing considerations addressed
- [ ] Health check endpoints implemented and tested

#### Imported: Common Issue Diagnostics

### Build Performance Issues
**Symptoms**: Slow builds (10+ minutes), frequent cache invalidation
**Root causes**: Poor layer ordering, large build context, no caching strategy
**Solutions**: Multi-stage builds, .dockerignore optimization, dependency caching

### Security Vulnerabilities
**Symptoms**: Security scan failures, exposed secrets, root execution
**Root causes**: Outdated base images, hardcoded secrets, default user
**Solutions**: Regular base updates, secrets management, non-root configuration

### Image Size Problems
**Symptoms**: Images over 1GB, deployment slowness
**Root causes**: Unnecessary files, build tools in production, poor base selection
**Solutions**: Distroless images, multi-stage optimization, artifact selection

### Networking Issues
**Symptoms**: Service communication failures, DNS resolution errors
**Root causes**: Missing networks, port conflicts, service naming
**Solutions**: Custom networks, health checks, proper service discovery

### Development Workflow Problems
**Symptoms**: Hot reload failures, debugging difficulties, slow iteration
**Root causes**: Volume mounting issues, port configuration, environment mismatch
**Solutions**: Development-specific targets, proper volume strategy, debug configuration

#### Imported: Limitations

- Use this skill only when the task clearly matches the scope described above.
- Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
- Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.