Building Docker Images
5 Topics
1
Writing Your First Dockerfile — Every Instruction Explained
FROM, RUN, COPY, ADD, CMD, ENTRYPOINT, and ENV rules.
Highly relevant for DevOps, SRE, and cloud developer roles. Expect detailed questions on CMD vs ENTRYPOINT, COPY vs ADD, and exec form vs shell form.
2
Multi-Stage Builds — Smaller, Faster, Safer Images
Compiling binaries in build containers and copying outputs to runtime images.
A cornerstone SRE concept. Interviewers will test your ability to refactor single-stage Dockerfiles to reduce storage footprints and minimize host security vulnerabilities.
3
Dockerfile Best Practices — Layer Ordering, .dockerignore, Non-Root Users
Structuring layers, reducing size, and running securely.
Essential for testing your production engineering skills. Be prepared to analyze a poorly written Dockerfile and identify layer issues, cache misses, and security holes.
4
Building Images for Different Architectures (ARM vs x86)
Utilizing Docker Buildx and QEMU to target multiple CPUs.
Highly relevant in modern platform engineering. You must explain how to build a single container tag that runs seamlessly on both Apple M-series developer laptops and Intel/AMD cloud servers.
5
Distroless and Scratch Images — Minimal Containers for Production
Stripping out OS commands and package managers for ultra-secure deployments.
Crucial for security-compliance audits. Interviewers will check if you know how to build shell-less containers and how to debug them without tools like apt or bash.