Module 8 Lesson 5: Dev vs. Prod Dockerfiles

You shouldn't use the exact same Docker setup for Development and Production. Their goals are different.

Goal	Development	Production
Speed	Instant startup (Hot reload)	Faster downloads (Small size)
Visibility	Verbose logs & Debuggers	Silent & Secure
Permissions	"Root" is fine for speed	Non-Root only
Tools	Includes Compilers & Linters	Minimal app only

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1. Approach A: Two Separate Files

Perfect for simpler projects.

• Dockerfile.dev: Starts with a full base image, uses npm start or pip watch.
• Dockerfile: Uses multi-stage builds and a slim base for production.

Usage:

# To run locally
docker build -f Dockerfile.dev .

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2. Approach B: Multi-Stage "Targets" (The Pro Way)

You can use a single Dockerfile with different "End States" (Targets).

# 1. Base Layer
FROM node:18-alpine AS base
WORKDIR /app
COPY package*.json ./
RUN npm install

# 2. Development Stage
FROM base AS development
COPY . .
CMD ["npm", "run", "dev"]

# 3. Production Stage
FROM base AS production
COPY . .
RUN npm run build
RUN rm -rf src/ # Cleanup
USER node
CMD ["npm", "start"]

Usage:

# Build only up to the 'development' stage
docker build --target development -t app:dev .

# Build everything up to the 'production' stage
docker build --target production -t app:prod .

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3. Best Practices Table

Feature	Dev Config	Prod Config
Source Code	Bind Mounted	COPY instruction
Secrets	.env file	Docker Secrets
Base Image	Regular (e.g. node:18)	Alpine/Slim (e.g. node:18-slim)
Caching	Aggressive	Security-focused
User	Root (usually)	Non-root

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Exercise: The Environmental Audit

1. Look at your project's current Dockerfile. Which goal is it optimized for: Dev or Prod?
2. Identify three things in that file that are "Unsafe" for production (e.g., source code inside, running as root).
3. Rewrite it using the Multi-Stage Targets approach described above.
4. Why is it better to use "Targets" in one file rather than having two separate files? (Hint: Think about maintaining the shared RUN npm install instructions).

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Conclusion of Module 8

You have completed the Development Deep Dive. You now know how to build a local environment that is fast, consistent, and easily bridgeable to production.

Next Module: The advanced storage layer: Module 9: Docker Volumes in Depth.