docker

name	docker
description	Docker and containerization best practices including multi-stage builds, security, and Docker Compose.
globs	["**/Dockerfile","**/docker-compose.yml","**/docker-compose.yaml","**/.dockerignore"]
priority	80
tags	["devops"]

Docker Best Practices

Dockerfile

• Use specific base image tags (not :latest)
• Use multi-stage builds for smaller images
• Minimize layers (combine RUN commands)
• Copy package.json first for caching
• Run as non-root user
• Use .dockerignore

Example Multi-stage Build

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

FROM node:20-alpine AS runner
WORKDIR /app
RUN addgroup -g 1001 nodejs
RUN adduser -S nodejs -u 1001
COPY --from=builder /app/dist ./dist
USER nodejs
CMD ["node", "dist/index.js"]

Docker Compose

• Use version 3.8+
• Define healthchecks
• Use named volumes for persistence
• Configure restart policies
• Use environment files

Security

• Scan images for vulnerabilities
• Don't run as root
• Use secrets for sensitive data
• Keep base images updated
• Use distroless/alpine images

Performance

• Use BuildKit
• Leverage layer caching
• Use .dockerignore
• Minimize image size