📦Skill assessment · 168 questions

Containerization skill assessment

Build small, run safe, ship anywhere.

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What it covers

Images & Layers

Understand how images are built from stacked, cached layers and addressed by tags/digests. This governs build speed, image size, and reproducibility.

Union/overlay filesystem and layer cachingImage vs container; writable layer & copy-on-writeTags vs immutable digestsOCI image spec and registriesReducing image size

Dockerfiles & Builds

Write Dockerfiles that build fast and small by ordering instructions for cache reuse and using multi-stage builds.

RUN/COPY/ADD/CMD/ENTRYPOINT/ARG/ENV semanticsLayer ordering and cache bustingMulti-stage builds and COPY --fromCMD vs ENTRYPOINT (shell vs exec form).dockerignore and BuildKit

Runtime & Networking

Know how containers run as processes, handle signals as PID 1, and talk to each other and the host over networks.

Container lifecycle and PID 1 signal/zombie handlingPort publishing with -pbridge vs host vs none networksDNS-based service discovery between containersRestart policies

Storage & Data

Containers are ephemeral; learn how to persist and share data correctly across restarts and rebuilds.

Named volumes vs bind mounts vs tmpfsWhere the writable layer livesData persistence across container recreationVolume drivers

Compose & Multi-container

Use Compose to define multi-container apps locally, and recognize when you've outgrown it and need an orchestrator.

services, networks, volumes in compose filesdepends_on and its limits (no readiness wait)Environment and .env handlingProfiles and scalingWhen to graduate to Kubernetes

Security

Shrink the container attack surface: drop privileges, minimize capabilities, and keep secrets out of images.

Running as non-root (USER) and rootless modeDropping Linux capabilities; avoiding --privilegedRead-only root filesystemImage scanningWhy secrets in ENV/ARG/layers leak

Registries & Distribution

Images have to live somewhere and move between environments safely. Know how registries store, tag, and authenticate image pulls/pushes.

Docker Hub vs private/self-hosted registries (ECR, GCR, Harbor)docker login, credential helpers, and registry authPushing/pulling by tag vs digest for reproducible deploysImage signing and verification (Docker Content Trust, cosign)Rate limits and mirroring/pull-through caches

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