Docker Tutorial — Docker FAQ
Frequently asked questions about Docker, answered clearly and concisely.
General Questions
Q: Is Docker free?
Show Answer
Docker Engine is free and open source (Apache 2.0 license). Docker Desktop is free for personal use, education, and small businesses (fewer than 250 employees AND less than $10M revenue). Larger organizations need a paid subscription.
Q: Docker vs Podman — which should I learn?
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Learn Docker first — it’s the industry standard with the largest ecosystem. Podman is a Docker-compatible alternative that’s rootless and daemonless. Skills transfer directly between them because both follow OCI standards.
Q: Do I need Docker to learn Kubernetes?
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You need to understand container images and Dockerfiles, but Kubernetes uses containerd (not Docker) as its runtime. Learn Docker basics → Dockerfile → image building, then move to Kubernetes.
Q: Should I use Alpine or Debian-based images?
Show Answer
Alpine images are smaller (5MB base) but use musl libc instead of glibc, which can cause compatibility issues. Debian-slim images are larger (~80MB) but more compatible. For production, test both and choose what works for your application.
Q: How do I keep Docker images secure?
Show Answer
- Use official base images with specific version tags (never
:latest) - Run as non-root user (
USERinstruction) - Scan images for vulnerabilities (Trivy, Docker Scout)
- Use multi-stage builds to minimize attack surface
- Keep base images updated regularly
