Last week I successfully passed the CKA exam, and I wanted to give some pointers on how to best study for it.
Obviously I can’t discuss any of the exam content. You’ll need to know a lot more than what I’ve listed here in terms of deploying and managing Kubernetes. I’ve only covered some basics–though I think the information on kubectl generators will really help. Kubernetes the hard way is also useful.
Here are a few basic skills you will need to pass the exam. Well, even to take the exam.
Again, there is quite a bit more you will need to know, especially about deploying and managing Kubernetes, but these are the basics. Checkout the curriculum for more ideas on what to study.
Exam Time Management
It’s a three hour exam and I expect that most people will use the entire time. Questions have differing levels of difficulty and value. You are allowed to open a note pad in the exam browser application, so it’s a good idea to take notes on what questions have what value and which one’s you have completed. Definitely figure out a strategy for picking which questions to answer first, and last.
Linux Command Line
You need to be comfortable with the Linux command line. The basics would be Ok. If you can change directories, open files with vim, and run kubectl you will probably be fine.
Command Line Text Editor
This is a big one. If you are not capable of opening and closing vim (or nano), typing into it, and search and replace, the exam will likely not be possible to pass. I would suggest being very comfortable with vim. Search and replace is a good skill to have: :s/new/old/g. :x is the same as :wq. :)
Generating YAML with kubectl
It’s easy to create a deployment from the command line and then export the YAML. Actually there are several generators. Using kubectl run with different options can create: pods, deployments, replication controllers, jobs, and cron jobs.
First create a deployment with the run command. Without any options a deployment is created.
master $ kubectl run --image nginx nginx
deployment.apps/nginx created
Now we can export the YAML that kubectl generated behind the scenes.
Note the --export option.
master $ kubectl get deploy nginx -o yaml --export
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
annotations:
deployment.kubernetes.io/revision: "1"
creationTimestamp: null
generation: 1
labels:
run: nginx
name: nginx
selfLink: /apis/extensions/v1beta1/namespaces/default/deployments/nginx
spec:
progressDeadlineSeconds: 600
replicas: 1
revisionHistoryLimit: 2
selector:
matchLabels:
run: nginx
strategy:
rollingUpdate:
maxSurge: 25%
maxUnavailable: 25%
type: RollingUpdate
template:
metadata:
creationTimestamp: null
labels:
run: nginx
spec:
containers:
- image: nginx
imagePullPolicy: Always
name: nginx
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
dnsPolicy: ClusterFirst
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
terminationGracePeriodSeconds: 30
status: {}
The best thing to do is to export that to a file.
kubectl get deploy nginx -o yaml --export > nginx-deploy.yml
Then delete that deploy if you don’t need it.
kubectl delete deploy nginx
Now we have an example deployment that can be used to create other deployments…a base file effectively.
To generate a YAML for a pod, use --restart=Never
master $ kubectl run nginx --image=nginx --port=80 --restart=Never
pod/nginx created
master $ kubectl get pod nginx -o yaml --export
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: nginx
SNIP!
Remember that other options can create jobs, cron jobs, recplication controllers, etc.
To practice generating YAML you don’t need much more than a Katacoda playground.
kubernetes.io/docs
This is a very useful page. Get used to being able to search it and find the documents for key resources.
Editing YAML Live
In some cases it might be easiest to edit the YAML live.
kubectl edit deploy nginx
This will open up the YAML for the nginx deploy in $EDITOR, ie. vim. When you close it, the new YAML will be applied (or if the YAML has errors then it will error and reopen in vim, like visudo if you’ve ever used it).
The CKA exam is a tough one, but mostly due to time limitations and the fact that you need to generate a lot of YAML quickly, without cutting and pasting. I think the CKA is a good certification to get at this point in time, and I’m glad that I only had to write it once.