Dockerfile Builder
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FROM node:20-alpine AS base
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WORKDIR /app
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COPY package*.json ./
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RUN npm install --production
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COPY . .
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EXPOSE 3000
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CMD ["node", "src/index.js"]
Instruction Insight
FROM node:20-alpine
The foundation. Multi-stage builds often start with a lightweight "Alpine" linux base to minimize security surface area and image size.
Resulting Layer: Root filesystem with Node.js runtime (~50MB)
Build Layer Stack
node:20-alpine
Base Image
npm install
Dependencies
COPY . .
App Source
Virtualization Models
Virtual Machine
Hardware
Hypervisor
Guest OS
Bins/Libs
App
Container
Hardware
Host OS / Kernel
Container Runtime
Bins/Libs
App
Containers share the Host OS Kernel, making them lightweight and fast to start compared to the bulky Guest OS overhead of VMs.
Multi-Service Orchestration (docker-compose.yml)
services:
web:
build: .
ports: ["3000:3000"]
depends_on: [db, cache]
environment:
- DB_URL=postgres://db:5432
db:
image: postgres:15-alpine
volumes:
- pgdata:/var/lib/postgresql/data
cache:
image: redis:alpine
restart: always
Service: Web
The main application service. depends_on ensures the database and cache containers start before the app, while ports maps the internal traffic to your host.