Docker is easy to learn but hard to master. Here are 10 mistakes almost everyone makes.
1. Using :latest Tag¶
Docker: 10 Mistakes Every Beginner Makes¶
✅ FROM node:20.11-alpine¶
2. Running as Root¶
RUN addgroup -S app && adduser -S app -G app USER app
3. Huge Images¶
Use multi-stage builds and Alpine:
FROM node:20 AS build WORKDIR /app COPY package*.json ./ RUN npm ci COPY . . RUN npm run build
FROM node:20-alpine COPY –from=build /app/dist ./dist CMD [“node”, “dist/index.js”]
4. Wrong Layer Order (Cache)¶
✅ Dependencies first, then code¶
COPY package*.json ./ RUN npm install COPY . .
5. Missing .dockerignore¶
node_modules .git .env Dockerfile
6. Secrets in Image¶
Never put passwords in Dockerfile. Use runtime env or Docker secrets.
7. Multiple Processes in One Container¶
One container = one process. Don’t turn containers into VMs.
8. No Health Check¶
HEALTHCHECK –interval=30s –timeout=3s CMD curl -f http://localhost:3000/health || exit 1
9. No Volumes for Data¶
docker run -v pgdata:/var/lib/postgresql/data postgres:16
10. No Resource Limits¶
docker run –memory=512m –cpus=1.0 myapp
Summary¶
Follow best practices from the start. Fixing bad habits is harder than not learning them.