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Skill: ops-docker

Fork

Docker and Docker Compose containerization. Trigger when the user wants to dockerize an application or create containers.

Configuration​

PropertyValue
Contextfork
Allowed toolsRead, Write, Edit, Bash, Glob, Grep
Keywordsops, docker

Detailed description​

Docker Containerization

Multi-Stage Dockerfile​

# Stage 1: Build
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# Stage 2: Production
FROM node:20-alpine AS runner
WORKDIR /app
ENV NODE_ENV=production

RUN addgroup -S appgroup && adduser -S appuser -G appgroup
USER appuser

COPY --from=builder --chown=appuser:appgroup /app/dist ./dist
COPY --from=builder --chown=appuser:appgroup /app/node_modules ./node_modules

EXPOSE 3000
HEALTHCHECK CMD wget -q --spider http://localhost:3000/health || exit 1
CMD ["node", "dist/index.js"]

Docker Compose​

version: '3.8'

services:
  app:
    build: .
    ports:
      - "3000:3000"
    environment:
      - DATABASE_URL=postgres://user:pass@db:5432/app
    depends_on:
      db:
        condition: service_healthy

  db:
    image: postgres:16-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:?required}
      POSTGRES_DB: app
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U user -d app"]
      interval: 10s
      timeout: 5s
      retries: 5

volumes:
  postgres_data:

Best practices​

  • Multi-stage builds to reduce size
  • Non-root user for security
  • .dockerignore to exclude unnecessary files
  • Health checks for availability
  • Labels for metadata

Automatic triggering​

This skill is automatically activated when:

  • The matching keywords are detected in the conversation
  • The task context matches the skill's domain

Triggering examples​

  • "I want to ops..."
  • "I want to docker..."

Context fork​

Fork means the skill runs in an isolated context:

  • Does not pollute the main conversation
  • Results are returned cleanly
  • Ideal for autonomous tasks

Practical examples​

1. Example: Multi-stage Dockerfile with Docker Compose​

Example: Multi-stage Dockerfile with Docker Compose

Scenario​

A Node.js API with PostgreSQL needs an optimized production image and a local dev setup.

Multi-stage Dockerfile​

# Dockerfile
# Stage 1: Dependencies
FROM node:20-alpine AS deps
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci --ignore-scripts

# Stage 2: Build
FROM node:20-alpine AS build
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
RUN npm run build
RUN npm prune --production

# Stage 3: Production
FROM node:20-alpine AS production
RUN addgroup -S appgroup && adduser -S appuser -G appgroup
WORKDIR /app
COPY --from=build /app/dist ./dist
COPY --from=build /app/node_modules ./node_modules
COPY --from=build /app/package.json ./
USER appuser
EXPOSE 3000
HEALTHCHECK --interval=30s --timeout=3s CMD wget -qO- http://localhost:3000/health || exit 1
CMD ["node", "dist/main.js"]

Docker Compose (local dev)​

# docker-compose.yml
services:
  api:
    build:
      context: .
      target: deps
    volumes:
      - .:/app
      - /app/node_modules
    ports:
      - "3000:3000"
    environment:
      DATABASE_URL: postgresql://app:secret@db:5432/myapp
      NODE_ENV: development
    depends_on:
      db:
        condition: service_healthy
    command: npm run dev

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: app
      POSTGRES_PASSWORD: secret
      POSTGRES_DB: myapp
    ports:
      - "5432:5432"
    volumes:
      - pgdata:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U app -d myapp"]
      interval: 5s
      timeout: 3s
      retries: 5

volumes:
  pgdata:

Key Decisions​

  • Multi-stage: Final image ~150MB vs ~900MB with full build deps
  • Non-root user: appuser for security (no root in production)
  • Healthcheck: Docker monitors container health automatically
  • Volume mount: Dev gets live-reload via bind mount, node_modules excluded
  • Service dependency: condition: service_healthy ensures DB is ready before API starts

See also​