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Docker Essentials

Containerize applications with reproducible images and lean layers.

Why it matters

Docker images make builds repeatable across laptops and CI.

Core steps

  • Start from a slim base image and pin versions.
  • Copy only what you need and use multi-stage builds to keep images small.
  • Set a non-root user for better security.
  • Healthcheck critical services to fail fast in orchestration.

Example Dockerfile

FROM node:20-slim AS build
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM node:20-slim
WORKDIR /app
COPY --from=build /app/.next ./.next