Master K8s to nail the Docker Certified Associate exam
By: Cristovao Cordeiro
Tags: Containers, Docker Certification, Kubernetes, Docker, K8s

How did I prepare for the DCA exam

The DCA study guide is simply what it says: a guide! And from that guide, you can choose to either:

read the whole docs from Docker, Mirantis and Kubernetes, or for each study topic on the DCA study guide, cherry-pick the best learning sources, and focus only on that.

I’ve chosen 2. For two reasons: first, I’m not new to Docker and second, I’m not really an avid reader, so I prefer to be pragmatic and focus on the essential.

If you like to consume literature and play it safe, then no need to keep reading this article. On the other side, if you’re looking for some shortcuts, here it goes (note I have no affiliation with the following resources).

The best documentation matches for the DCA study guide

There are plenty of GitHub repositories were people have compiled lists of links, pointing to the best sources of documentation that match the DCA study guide topics. This is super up to date, and thus my favorite one:

Keep a diary

Yep, it sounds strange but I did it and it helped me a lot. My suggestion is, keep a text document (or a notebook) always open next to you, and make sure you write down all the important finding. These can vary from things that you have a hard time understanding, to cool features you’ve just discovered.

Practice exams

There are soooo many! Some paid, some free…are they worth spending the time? Yes, they give you a decent baseline and sometimes very accurate examples of what to expect in the real exam. Are they enough to pass the exam? I don’t think so!

Here are my top 3 (free):

“250 Practice Questions for the DCA Exam” - a set of DCA-tailored and Docker-specific questions, written by a fellow Medium.com member: https://medium.com/bb-tutorials-and-thoughts/250-practice-questions-for-the-dca-exam-84f3b9e8f5ce

- a set of DCA-tailored and Docker-specific questions, written by a fellow Medium.com member: https://medium.com/bb-tutorials-and-thoughts/250-practice-questions-for-the-dca-exam-84f3b9e8f5ce “Docker Certified Associate Exam Practice Test” - also written by a fellow Medium.com member, this compilation is purely about Kubernetes! I found it quite relevant, and even if the examples do not cover every possible question you might get, it will for sure get you acquainted with the Kubernetes subjects targeted in the DCA exam: https://medium.com/@jonathan.middaugh/docker-certified-associate-exam-practice-test-e1497ada96f6

- also written by a fellow Medium.com member, this compilation is purely about Kubernetes! I found it quite relevant, and even if the examples do not cover every possible question you might get, it will for sure get you acquainted with the Kubernetes subjects targeted in the DCA exam: https://medium.com/@jonathan.middaugh/docker-certified-associate-exam-practice-test-e1497ada96f6 chercher.tech - it’s like a repository of practice exams. Note that many questions are repeated, and some are even wrong! But still, I found it useful, and on the plus side, detecting those error will boost your confidence: https://chercher.tech/docker-certification/docker-certified-associate-dca-certification-practice-exams-set-1

I’ve done all of these, back to back, multiple times!

Courses:

To be honest, I haven’t done any. If you’re willing to spend the extra bucks, then yes, I’d say: do a few.

If I knew what I know now…

As I said, I’m writing this post a couple of days of taking the exam, so everything is still quite fresh in my mind.

The exam

55 questions: 13 reviewable multiple choice questions and 42 DOMC immutable ones. DOMC is harder than multiple choice! And on top, it triggers that diabolic nervous feeling on back of your head, which urges you to mark the potentially correct answer as incorrect when you’re not 100% sure.

Plain and simple, these were some of the topics that caught me off guard:

How to re-access a previously claimed PersistentVolume that has a reclaimPolicy=”retain”?

How to resize an existing PersistentVolume?

How to let a container from namespace X ping a service running on namespace Y, by DNS name?

What happens to a container when the readiness probe fails?

Can a UCP user with a RestrictedControl permissions create networks?

What’s the best strategy to deploy DTR caches?

Can you change the default location of “secrets” on the host?

Then obviously, many other questions in the exam are as expected and within the Docker realm. So don’t get me wrong, you still need to be proficient with commands like:

docker system COMMAND

docker image COMMAND

docker login

docker container COMMAND

docker swarm COMMAND

docker service COMMAND

docker stack COMMAND

docker save

docker load # you also need to know COMMAND arguments such as

--health-interval, -p, --endpoint-mode, --memory-limit, --format...

Finally, as a side note, I personally found the questions and answers’ phrasing inadequate for a professional certification. I’ve in fact made multiple comments during the exam (yes you can do that) to point out such flaws. I’ll give you an example. If I ask you:

How do you remove all dangling images?

Option 1: run `docker system prune`