233 lines
8.7 KiB
Markdown
233 lines
8.7 KiB
Markdown
---
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title: "3 weeks, 1 CKA"
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subtitle: "How to rock the k8s certification in no time"
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date: 2022-10-29
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draft: false
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author: Wilfried
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tags: [ops, containers, certifications, devops, kube]
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---
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## Kube & the CKA
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[Kube](https://kubernetes.io/), **k8s** or Kubernetes is the industry leader
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when you need to orchestrate some containers at scale. The **containers war** is
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over : Swarm, Mesos and all other alternatives are dead (except
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[Nomad](https://nomadproject.io) under some circonstances).
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The **Certified Kubernetes Administror** (CKA) is a certification delivered by
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the **Cloud Native Coputing Fundation** (CNCF) and the **Linux Fundation** that
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will ensure that the certified peoples have the skills and knowledge to operate
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as cluster administrators.
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As a certified kube nerd, I can now confirm that this certification is much more
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than a _cool line_ on your CV.
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## My CKA story
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My certification was funded (price is around 300$) by my previous job (a year
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ago). At that time, I was working as a DevOps/CI guy on a SaaS product based on
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Gitlab, Gitlab-CI and Docker. Containers at a high or low-level was part of my
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day to day job [^1].
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For various reasons I quit and I am now working as a fullstack dev (Rails/React)
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so I just use containers to spin up my dev env. Due to this change I did almost
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have no time to dig on kube and the deadline to pass my exam was getting closer
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and closer 🚨
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On October I kicked myself in the ass to rush out the CKA and pass my exam ASAP.
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**3 weeks later I am now certified ! YAY !** (with a 85% score)
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Enough about me, now I will share with you everything you need to know to
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prepare and pass your's !
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## Course Material
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When looking for learning materials, I focused my search on courses labelled as
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**CKA courses** only (other ones do not go deep enough). The best one out
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there is _Certified Kubernetes Administrator (CKA) with Practice Tests_ by
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Mumshad Mannambeth on
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[Udemy](https://www.udemy.com/course/certified-kubernetes-administrator-with-practice-tests/)
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(reddit agrees with me so, it should the truth 🤷).
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The awesomeness of this course comes from on how the content is balanced between
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videos on theory and concepts around kube (architectures, entities and so on)
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followed by hands on-labs. Directly from your browser, you will be able to
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practice and
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**get your hands dirty** by typing some "kube cuddle" commands on a multi-nodes
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cluster setup. Tasks in each labs is clear enough for you to get the solution
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by yourself or by the official kube docs. Of course, you can always take a look
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at the associated video if you are stuck or want to confirm that your way of
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doing things is the right one.
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If you want to rush out, you should be able to finish the course by a week or
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two, the rest of the time will be labs, labs, labs and labs. This certification
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is a practical one and **you need to practice a lot**.
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## Exam Prep Materials
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When you starting to feel that you can control some **kube powers** with your
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hands it's time to go on practice tests. Starts with the one in the course by
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Mumshad. In order to pass the CKA you need to be efficient on a bunch of
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various tasks. Practice pratice practice in order to become fluent in a least :
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- cluster upgrades using kubeadm
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- etcd back/restore
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- pods scheduling (with PV and PVC)
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- deployments and scheduling (with PV and PVC)
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- roles setup (users, Role/RoleBinding, ClusterRole/ClusterRoleBinding)
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- troubleshooting pods
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- troubleshooting cluster components
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in order to sharpen your skills, use the labs on [killer.sh](https://killer.sh).
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You will have two "free sessions" attached to your Linux Fundation profile. Be
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careful, those exams are way more difficult that the real ones. Hopefully this
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will give you a very accurate feeling of your capabilities when times maters.
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Take time to review the answers as they will give you deep explanations on the
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how and why. Killer.sh interface is quite the same as the one you will use in
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the real exam so take time to check the setup and customize it the way you like.
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Now you are ready, go for the exam day !
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## Exam Day
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On the exam day, prepare yourself and your environment well. You can access the
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session 30 minutes before the exam starts. Use this time to setup your desk and
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your room. You need to be a in quiet and empty room with nothing on your desk to
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speed up the check-in. The exam proctor will first ask you for your ID. After
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that you will go for a room tour, an usb connected webcam is prefered since your
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need to turn it in all directions for the proctor to verified you're not
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cheating.
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During the exam, the only online resource accessible is the [kubernetes
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documentation](https://kubernetes.io/docs). No worry, this is the only thing you
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need. I can recommend enough to use it why you are learning to be very
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comfortable with it on the exam day.
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Do not stress out, take your time, at least you have a free retake if you miss
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the first one !
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## Tricks and Tips
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CKA is about speed and efficiency, here are some usefull tips.
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### UTFD : Use The Fucking Documentation
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k8s documentation is a gem, everything is already there but you have to know
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some shortcuts to quckly access the examples or articles your need. **USE THE
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SEARCH** to quickly find yaml manifests for things like PV, PVC. Just type PV
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and rush the first link!
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Another usefull page in the documentation is the [kubectl cheat
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sheet](https://kubernetes.io/docs/reference/kubectl/cheatsheet/), as usual, just
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type "cheat sheet" and you are good to go!
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### kubectl : be imperative first
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k8s is about carefully handcrafted yaml manifest, right ? That's too slow in our
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case. You need to be fast. Hopefully, `kubectl` can do 90% of the job for you.
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Always use the **imperative approach** as a first intention. Let's imagine you
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need to run an ngnix POD:
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```sh
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kubectl run nginx --image=nginx
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```
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or if you need to create a service :
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```sh
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kubectl create service clusterip my-service --tcp=5678:8080
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```
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Sometimes, some of the options are not configurable using the cli, no worry,
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`kubectl` have your back too ! You can generate a yaml manifest directly from
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the cli :
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```sh
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kubectl run nginx --image=nginx --labels tier=frontend --dry-run=client -o yaml > pod.yaml
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```
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By redirecting it to a new text file, you will then be able to add the missing
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specs from a vim session followed by a `kubectl apply -f` to apply your changes.
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There is also a lot of examples in help messages from the cli ! Before loosing
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time changing windows from terminal to browser, append `-h` to your command !
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[^2]
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_Extra tip! If you need to generate a DaemonSet or StatefulSet, you can not do
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it directly from the cli but since thoose specs are similar to a deployment one,
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generate a deployment and edit it afterward._
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Finally practice some `jsonpath` stuff and play with it to output data from
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pods, nodes, the way you want.
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### Take the time to setup your env
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The vitual machine you will be working on is a simple Ubuntu with a stock XFCE
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config. Base setup for the shell/ssh and VIM (colors etc) will be applied by
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default. Here is the things I think is worth it to add in the bash config :
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```sh
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# optional, should already be setup
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alias k='kubectl'
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# for fast apply
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alias kaf='kubectl apply -f'
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# old habit..
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alias vi='vim'
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# save tedious typos
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export do='--dry-run=client -o yaml'
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# we are in a hurry, we do not want to wait for things to terminate gracefully
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export now='--force --grace-period 0'
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# just to organize things, useful while reviewing our answers
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function mkcd {
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cd $HOME && mkdir -p $1 && cd $1
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}
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```
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### Known your VIM
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Due to the time constraint, I did not recommend working outside the terminal,
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except for Firefox and navigating the docs (since you are in a remote desktop,
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everything feels a little bit slow).
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Some efficiency with VIM will be a great plus for the overall exam. At least
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knowing the basic on how to edit/navigate/save the file is a must have. I also
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recommend getting confortable with :
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- basic moves: h,j,k,l,b,w,e
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- visual mode
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- copy/paste
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- advanced moves : t/T, f/F
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- search/replace
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- :N to jump to line N
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### Shell basics
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Some shell basics are also a great plus, the most important one is `Ctrl+R` for
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reverse searching a command in your history. Add to that some stuff like `!$` to
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recall the last arg from your previous command, you should be able to have a
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flow like this :
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```sh
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vi somestuff.yaml
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kaf !$
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```
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Sometime, you may need to filter/modify output provided by a command, some shell
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basic like `grep`, `cut`, `tail`, `head` may help you. If you already know some
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shit about `AWK`, be sure to also review it a little bit, this tool is dope and
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can archive very impressive stuff.
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Now, it's your turn.
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```sh
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kubectl apply -f goodluck.yaml
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```
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[^1]: Kudos @athoune
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[^2]: Another shell tip ! `!! -h` to recall your last command with the extra `-h`
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