Generates multi-stage Dockerfiles and docker-compose.yml configurations, adds services like Postgres/Redis/Celery/Nginx, and checks for Docker anti-patterns. Use when asked to "dockerize", "create dockerfile", "docker compose", "add docker", "add redis", "add postgres", "docker init", "optimize docker", or "container setup".
Generate production-ready Dockerfiles and docker-compose configurations, add common services, and audit existing Docker setups for anti-patterns.
This skill supports three subcommands: /docker init, /docker add <service>, and /docker optimize.
/docker init -- Generate Dockerfile + compose(Python/Node/Go) and framework:
# Python detection
ls requirements.txt pyproject.toml Pipfile setup.py 2>/dev/null
# Node detection
ls package.json 2>/dev/null
# Go detection
ls go.mod 2>/dev/null
Detect package manager and dependency files:
Generate a multi-stage Dockerfile:
# Example: Python multi-stage
FROM python:3.12-slim AS builder
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
FROM python:3.12-slim
RUN useradd --create-home appuser
WORKDIR /app
COPY --from=builder /usr/local/lib/python3.12/site-packages /usr/local/lib/python3.12/site-packages
COPY . .
USER appuser
EXPOSE 8000
CMD ["python", "-m", "uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]
Generate docker-compose.yml with:
.envversion: "3.9"
services:
app:
build: .
ports:
- "8000:8000"
volumes:
- .:/app
env_file:
- .env
healthcheck:
test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
interval: 30s
timeout: 10s
retries: 3
Generate .dockerignore if not already present, including common exclusions:
.git
.venv
__pycache__
node_modules
.env
*.pyc
.mypy_cache
.pytest_cache
Present all generated files for review before writing to disk.
/docker add <service> -- Add a serviceRead the existing docker-compose.yml to understand current services, networks, and volumes.
Add the appropriate service block based on the requested service name:
postgres: PostgreSQL with health check, persistent volume, and environment variables
postgres:
image: postgres:16-alpine
environment:
POSTGRES_DB: app_db
POSTGRES_USER: app_user
POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-changeme}
volumes:
- postgres_data:/var/lib/postgresql/data
healthcheck:
test: ["CMD-SHELL", "pg_isready -U app_user -d app_db"]
interval: 10s
timeout: 5s
retries: 5
redis: Redis with persistence and health check
redis:
image: redis:7-alpine
command: redis-server --appendonly yes
volumes:
- redis_data:/data
healthcheck:
test: ["CMD", "redis-cli", "ping"]
interval: 10s
timeout: 5s
retries: 5
celery: Celery worker using the same image as the app service, depends_on app
celery:
build: .
command: celery -A app worker --loglevel=info
depends_on:
- app
- redis
env_file:
- .env
celery-beat: Celery beat scheduler
celery-beat:
build: .
command: celery -A app beat --loglevel=info
depends_on:
- celery
env_file:
- .env
nginx: Nginx reverse proxy with configuration volume
nginx:
image: nginx:alpine
ports:
- "80:80"
volumes:
- ./nginx.conf:/etc/nginx/conf.d/default.conf
depends_on:
- app
mailhog: Development email catcher
/docker optimize -- Check for anti-patternsRead the Dockerfile and docker-compose.yml from the project root.
Check for common issues:
| Check | Severity | What to look for |
|---|---|---|
| Running as root | High | No USER directive in Dockerfile |
| No .dockerignore | Medium | Missing file or missing key entries (.git, node_modules, .env) |
| COPY before deps | Medium | Source copied before dependency install, breaking layer cache |
Using latest tag | Medium | Base image uses :latest instead of a pinned version |
| No health checks | Medium | No HEALTHCHECK in Dockerfile or healthcheck in compose |
| Bloated final image | Low | Build tools (gcc, make) present in production stage |
| Secrets in env/args | High | Passwords or tokens in ENV or ARG directives |
| No multi-stage build | Low | Single FROM with both build and runtime dependencies |
Present findings with severity level and a concrete fix suggestion for each issue:
[HIGH] Running as root
-> Add USER directive: RUN useradd -m appuser && USER appuser
[MEDIUM] Using latest tag for base image
-> Pin version: python:3.12-slim instead of python:latest
Offer to apply fixes automatically where possible (adding USER, reordering COPY, pinning tags).
| Problem | Cause | Solution |
|---|---|---|
| Project type not detected | No recognizable dependency files | Manually specify the language and framework |
| Conflicting ports | Another service already uses the requested port | Change the host port mapping in docker-compose.yml |
| Service name conflicts | A service with the same name already exists in compose | Choose a different name or update the existing service |
| Health check fails | Application does not expose a health endpoint | Add a /health endpoint to your application or adjust the health check command |
| Permission denied errors | Non-root user cannot access mounted volumes | Ensure volume permissions match the container user UID |
mailhog:
image: mailhog/mailhog
ports:
- "1025:1025"
- "8025:8025"
Add necessary networks, volumes, and depends_on relationships to wire the new service into the existing compose graph.
Update the app service environment to reference the new service (e.g., add DATABASE_URL, REDIS_URL, or CELERY_BROKER_URL).
Present the updated compose file for review.