Day 3/40 - Multi Stage Docker Build - Docker Tutorial For Beginners - CKA Full Course 2024
Overview
This video is Day 3 of the 40-day CKA preparation course. It deep-dives into multi-stage Docker builds — a critical optimization technique for creating smaller, more secure container images by separating build-time dependencies from runtime artifacts. The instructor demonstrates why bloated images are a production anti-pattern and how multi-stage builds solve this problem.
Source Details
- Channel: Tech Tutorials with Piyush
- Playlist: 40 Days of Kubernetes (CKA Full Course)
- Companion Repository: piyushsachdeva/CKA-2024
- Challenge:
#40daysofKubernetes
Key Takeaways
1. Why Multi-Stage Builds Matter
- Smaller Images: Build tools (compilers, dev dependencies) don’t need to exist in production images.
- Enhanced Security: Fewer packages in the final image mean fewer CVE attack vectors.
- Faster Deployments: Smaller images pull and start faster in CI/CD pipelines.
- Best Practice: This is how real-world production images are built — critical for CKA and DevOps interviews.
2. The Problem with Single-Stage Builds
A single Dockerfile that builds AND runs in the same image:
- Includes build tools (e.g.,
gcc,node-gyp,maven) in the final image - Bloats image size by hundreds of MBs
- Exposes unnecessary attack surface
3. How Multi-Stage Builds Work
Use multiple FROM statements in a single Dockerfile. Each FROM starts a new stage. Only copy what you need into the final stage.
# Stage 1: Build
FROM node:18 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build
# Stage 2: Production (slim runtime)
FROM node:18-alpine
WORKDIR /app
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
COPY package.json .
EXPOSE 3000
CMD ["node", "dist/main.js"]4. Syntax Deep Dive
| Instruction | Purpose |
|---|---|
FROM image AS stage-name | Name a build stage for later reference |
COPY --from=stage-name source dest | Copy files from a previous stage |
COPY --from=builder /app/dist ./dist | Copy built artifacts only |
5. Size Comparison (Typical Results)
| Build Type | Image Size | Security Surface |
|---|---|---|
| Single-Stage (full base) | ~1.2 GB | High (includes build tools) |
| Multi-Stage (distroless/Alpine) | ~150 MB | Low (runtime only) |
| Reduction | ~85% | Dramatically improved |
6. CKA & Production Relevance
- Kubernetes pulls images from registries — smaller images = faster pod startup.
- Security scanning tools flag fewer CVEs in slim images.
- In resource-constrained clusters, image size directly affects node disk pressure.
Cross-References
- Dockerize a Project — includes multi-stage build patterns
- Docker Fundamentals
- CKA Certification Overview
- CKA Progress Tracker
Ingested: 2026-05-21