April 15, 2020

Preparing for CKA and CKAD

Some study tips you may not have found elsewhere for the Kubernetes CKA and CKAD exams

Which exam is harder? BOTH!

what's easier about CKAD

  • fewer challenges: 19 in 2 hours

  • mostly sticks to kubectl land

  • super relevant to SE work!

what's harder about CKAD

  • less time per challenge (19 / 120 minutes == ~6 minutes per)

what's easier about CKA

  • More time per challenge (8+ minutes per)

    • One hour extra time, but only 5 additional challenges (24 in 3 hours)

what's harder about CKA

  • Gotta know sysadmin for K8s and Etcd

    • Have your etcdctl, systemd, openssl basics down pat

Study resources

CKA

Administrator.]]

CKAD

Kubernetes the Hard Way

What it will teach you for CKA
  • etcd

  • certificate generation

  • order of bootstrapping nodes

What it will not teach you
  • Using kubeadm (used in the exams and in Konvoy)

  • examining and fixing certificates

  • lots of other stuff

    • The certificate generation was not useful in the exams - instead, you will need openssl to examine certificates and either openssl or kubeadm to refresh

Killer.sh - CKA and CKAD test simulators! (pay)   paid

https://killer.sh/

Resources that may be used during the exam

During the exam, only one non-tty tab can be open, and only the kubernetes.io or the kubernetes repo on github may be visited

Hip tips for both tests

Practice a lot with Gate One

This is the browser based shell that is used for the exams.

This is supposedly available to test at http://liftoffsoftware.com/Products/GateOne, but I have had zero success with the site. This mirrors the experience of many people on the intertubes.

Fortunately, I found a working container for this.

On Docker:

docker run  --name=gateone -p 443:8000 -d yovio/gateone

On K8s:

kubectl run gateone --image=yovio/gateone --restart=Never --port=443
kubectl expose pod gateone --port=8000 --target-port=443

Use Cloud load balancer or `kubectl port-forward` to access

Be fast with vim

  • Move/change/delete by word

  • Repeat command

  • Global search/replace

  • Multiline select and indent

Practice setup of alias and vim settings

vim settings in ~/.vimrc
set expandtab
set tabstop=2
set shiftwidth=2
Alias and auto-completion
  • Test that Bash completion is working with kubectl:

    kubectl conf<TAB>
    # should expand to kubectl config
  • Set your aliases in ~/.bashrc

    alias k='kubectl'
    alias k='kubectl config set-context --current --namespace '
    alias kx='kubectl config get-contexts'

Get awesome with imperative kubectl

Avoid editing YAML from scratch at all costs. The `kubectl run` command is being deprecated, but is availabe as of 1.16.x - so use it!

  # Create a pod
  k run mypod --image=nginx --restart=Never --labels=app=mypod
  # Create a Deployment - this is the default, so --restart may be omitted
  k run mydeployment --image=nginx --restart=Always --replicas=3
  # Create a Job
  k run myjob --image=nginx --restart=OnFailure
  # Create a Service
  k expose deploy mydeployment --port=8080 --target-port=80 --type=NodePort --name myservice
  # Create a DaemonSet by creating manifest for Deployment, then editing
  • Never create a service with YAML - use k expose

  • Test a service with k get ep

Learn some little about JSONPATH and –sort-by

Remember -o wide k get <manythings> and -o name for k get <anything>

Just prior to the exam

Assign C-w to an extension

This is to prevent accidentally closing the exam window! chrome://extensions -> Keyboard shortcuts

I use the Quick Tabs extension

Install/Enable the exam extension

Innovative Exams Screensharing

Disable all extensions other than the exam and the extension you assigned to C-w

Approach when first logged in

Step 1: Assure vim settings are correct in ~/.vimrc
  set tabstop=2
  set expandtab
  set shiftwidth=2
Step 2: suss environment
 w
 cat /etc/os-release
Step 3: install bash-completion and tmux

On CentOS/Red Hat

 sudo yum install bash-completion tmux
 source ~/.bashrc

On Debian/Ubuntu

 sudo apt install bash-completion
 source /etc/bash_completion
Step 4: aliases and completion
alias k='kubectl'
alias kn='kubectl config set-context --current --namespace '
alias kx='kubectl config get-contexts'
## notes file: add, edit, notes (view)
alias a='echo >> ~/.notes.txt '
## save my kubectl explain thangs in fast text files
source <(kubectl completion bash)
complete -F __start_kubectl k

© Greg Grubbs 2008-2020

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