Dockerfile Best Practices

📅 2026-06-12 | 📂 Docker

Introduction

A Dockerfile is a text file containing instructions to build a Docker image. Writing efficient Dockerfiles results in smaller images, faster builds, and better security.

Basic Dockerfile Structure

# Use a specific base image version
FROM python:3.11-slim

# Set working directory
WORKDIR /app

# Copy dependency file first (layer caching)
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Copy application code
COPY . .

# Expose port
EXPOSE 8000

# Run the application
CMD ["python", "app.py"]

Multi-Stage Builds

# Build stage
FROM node:18 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# Production stage
FROM node:18-slim
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
CMD ["node", "dist/server.js"]

Best Practices

# 1. Use .dockerignore
# .dockerignore
node_modules
.git
*.md

# 2. Minimize layers - combine RUN commands
RUN apt-get update && apt-get install -y 
    curl 
    wget 
    && rm -rf /var/lib/apt/lists/*

# 3. Use non-root user
RUN useradd -m appuser
USER appuser

Summary

Write efficient Dockerfiles by using multi-stage builds, leveraging layer caching, minimizing image size, and following security best practices like using non-root users.

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