baasith6/cursor-skills/adding-docker

Add Docker

Use this skill when the user asks to dockerize, containerize, or add Docker support to an application.

Steps

1. Detect the runtime — inspect package.json, requirements.txt, go.mod, Cargo.toml, etc. to determine the language and runtime.

1. Create a multi-stage `Dockerfile`

For Node.js (example):

```dockerfile FROM node:20-alpine AS base

FROM base AS deps WORKDIR /app COPY package.json package-lock.json ./ RUN npm ci --omit=dev

FROM base AS build WORKDIR /app COPY package.json package-lock.json ./ RUN npm ci COPY . . RUN npm run build

FROM base AS runner WORKDIR /app ENV NODE_ENV=production COPY --from=deps /app/node_modules ./node_modules COPY --from=build /app/.next ./.next COPY --from=build /app/public ./public COPY --from=build /app/package.json ./ EXPOSE 3000 CMD ["npm", "start"] ```

Adapt for the detected framework — adjust the build output directory, entry command, and base image.

1. Create `.dockerignore`

`` node_modules .next .git .env* *.md ``

1. Create `docker-compose.yml` (if the app has dependencies like a database or Redis):

```yaml services: app: build: . ports:

• "3000:3000"

env_file: .env depends_on:

• db

db: image: postgres:16-alpine environment: POSTGRES_DB: app POSTGRES_USER: postgres POSTGRES_PASSWORD: postgres volumes:

• pgdata:/var/lib/postgresql/data

volumes: pgdata: ```

1. Add npm scripts (optional)

``json { "docker:build": "docker build -t myapp .", "docker:run": "docker compose up" } ``

Notes

• Use Alpine-based images to minimize image size.
• Never copy .env files into the image — use env_file or runtime injection.
• For monorepos, use a .dockerignore that excludes sibling packages not needed by the target app.
• Add a HEALTHCHECK instruction for production deployments.