Docker for Developers: From Dockerfile to Production-Ready Images

Docker isn't just for DevOps teams. Every developer should know how to build efficient, secure container images. Here's a practical guide. Your First Dockerfile FROM python:3.12-slim WORKDIR /app COPY requirements.txt . RUN pip install --no-cache-dir -r requirements.txt COPY . . EXPOSE 8000 CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"] Multi-Stage Builds Keep images small by separating build and runtime: # Stage 1: Build FROM python:3.12 AS builder WORKDIR /app COPY requirements.txt . RUN pip install --no-cache-dir --prefix = /install -r requirements.txt # Stage 2: Runtime FROM python:3.12-slim WORKDIR /app COPY --from=builder /install /usr/local COPY . . EXPOSE 8000 CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"] Result: image goes from 1.2GB to ~200MB. Layer Caching Docker caches each layer. Order matters: # BAD: Any code change invalidates pip install cache COPY . . RUN pip install -r requirements.txt # GOOD: Dependencies cached unless require