Level 0 exam — Docker · GUIDINEE.COM

Exam — fresh questions

12 questions to validate the fundamentals with Idir: what Docker is for, installing and running hello-world, telling the 5 actors apart, and playing the full lifecycle.
Answer everything, then click Check: your score and explanations will appear.

0.1 · Recall

1. What is Docker's real strength compared with a classic installation?

Nothing special The application and its environment travel together in a versioned image It prints faster It looks nicer

The image packs the code AND its dependencies: the same package runs identically on every machine.

0.1 · Application

2. Idir's site works on his laptop but breaks on the test server (different Node and Redis). What should he do?

Put app, database and cache in a single latest container Give up Docker and rewrite everything Reinstall the server blindly until it passes Pack each role into a versioned image and run the same images everywhere

Same versioned image on laptop, test and production: same behavior everywhere, one role per container.

0.1 · Arbitration

3. A colleague says: "Docker replaces VMs and monitors everything, let's put it all in one container". Idir's verdict?

Accept: a single latest container for everything, monitoring included Refuse: the container shares the kernel (VM sometimes required), one role per container, and Docker neither orchestrates nor monitors Accept if we add more RAM Refuse: Docker is useless

Container ≠ VM (shared kernel), one container = one role, and Docker packs/runs without monitoring or backing up.

0.2 · Recall

4. Idir is on Windows and wants to install Docker. What does he pick and check?

Any installer found at random Two parallel engines with no checks Docker Engine alone with no Compose Docker Desktop (official packages) + WSL 2 and BIOS virtualization, then docker version

Desktop on Windows/macOS (WSL 2 + virtualization), Engine on Linux — always the official packages, a single engine.

0.2 · Application

5. Idir types docker run hello-world and reads the message. What did he just prove?

That client, daemon, registry and execution work That the network is down Nothing at all That the computer is new

The ritual crosses the whole chain: image download, container creation and execution.

0.2 · Application

6. After hello-world, Idir wants to read what just happened. Which commands?

docker images then docker ps -a: the downloaded image and the finished container Shut down the workstation at once Delete the daemon Rerun the installer

images shows the downloaded image, ps -a the finished container: the pull → run → ps trio.

0.3 · Recall

7. Which picture best describes the image / container pair?

The container holds the image The image runs, the container stores The image is the immutable mold, the container the living part that comes out of it Two synonyms

The image never changes; each container adds its ephemeral writable layer on top.

0.3 · Application

8. Idir launches web1 and web2 from nginx:1.27, then removes web2. What does he see with ps and images?

Everything is gone: image and neighbors erased The nginx:1.27 image and web1 survive: removing one part touches neither the mold nor the neighbors The registry is deleted The daemon stops

One image → N independent containers: rm targets the part, not the mold.

0.3 · Arbitration

9. Idir hesitates between nginx:latest and nginx:1.27 to freeze his tests. What does he decide?

Both are strictly identical latest: it is shorter to type No tag: Docker will guess nginx:1.27: latest freezes no version, especially not in production

The tag freezes the version (1.27, 16); latest follows the latest publication and breaks reproducibility.

0.4 · Application

10. Idir tests a disposable image and wants no exited ghosts. Which option does he add to run?

-e -d --rm -p

--rm removes the container as soon as it stops: no exited containers to purge.

0.4 · Application

11. The demo container runs but stays silent. In which order does Idir diagnose?

Close the terminal and leave Rerun run in a loop without looking docker logs demo first (see), then docker exec -it demo sh if needed (enter) Delete the image at once

Logs to see, exec to enter: most diagnoses stop at the logs.

0.4 · Arbitration

12. Demo must stop and disappear cleanly, check included. Which sequence does Idir validate?

docker stop demo then docker rm demo then docker ps -a to check Closing the terminal: it is the same docker kill -9 then nothing docker rm without stop on a living container

Polite stop (SIGTERM then SIGKILL), husk removal with rm, ps -a as proof — never close the terminal.

What's next?

Score ≥ 80%: move to Level 1 — images, tags and Docker Hub with Idir.
Score between 50% and 80%: revisit the failed section(s) (0.1 usage, 0.2 installation, 0.3 architecture, 0.4 lifecycle), reread the explanations above, then retake the test.
Score < 50%: reread all of level 0 while applying each 48h challenge (Docker/VM card, hello-world ritual, nginx trio, demo cycle) before retrying.
And after? Keep Idir's lifecycle memo and installation checklist: level 1 replays them on real images.