Add Docker
Use this skill when the user asks to dockerize, containerize, or add Docker support to an application.
Steps
- Detect the runtime — inspect
package.json,requirements.txt,go.mod,Cargo.toml, etc. to determine the language and runtime. - Create a multi-stage
DockerfileFor Node.js (example):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. - Create
.dockerignorenode_modules.next.git.env* *.md - Create
docker-compose.yml(if the app has dependencies like a database or Redis):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: - Add npm scripts (optional)
{"docker:build": "docker build -t myapp.", "docker:run": "docker compose up"}
Notes
- Use Alpine-based images to minimize image size.
- Never copy
.envfiles into the image — useenv_fileor runtime injection. - For monorepos, use a
.dockerignorethat excludes sibling packages not needed by the target app. - Add a
HEALTHCHECKinstruction for production deployments.