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Bonus Exercises

Shortcuts and Time Savers

Using an alias for kubectl

You might find it tedious to enter the kubectl every time you want to run a command. It helps a lot to set up an alias for the command.

$ alias k=kubectl
$ k version
Client Version: version.Info{Major:"1", Minor:"12", GitVersion:"v1.12.2", GitCommit:"17c77c7898218073f14c8d573582e8d2313dc740", GitTreeState:"clean", BuildDate:"2018-10-30T21:39:16Z", GoVersion:"go1.11.1", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"10", GitVersion:"v1.10.11", GitCommit:"637c7e288581ee40ab4ca210618a89a555b6e7e9", GitTreeState:"clean", BuildDate:"2018-11-26T14:25:46Z", GoVersion:"go1.9.3", Compiler:"gc", Platform:"linux/amd64"}

Setting the namespace per context

At the beginning of each question you will be provided a command you need to run in order to perform the operations against a specific cluster. Run the command at the beginning of each question. Additionally, you can also set the namespace for the question as a preference to avoid having to the type the --namespace=<namespace-of-question> parameter with every operation.

$ kubectl config set-context <context-of-question> --namespace=<namespace-of-question>

Deleting Kubernetes objects quickly

You might make mistakes when creating objects and will want to delete and recreate it. Deleting objects sometimes takes a while as Kubernetes attempts to do it gracefully. You do not want to wait for a graceful shutdown during the exam due to the time constraint. It's much faster to force the deletion.

$ kubectl delete pod nginx --grace-period=0 --force

Bash Commands

Appending to a file

Write a bash one-liner that writes the current date to the file ~/tmp/date.txt every 5 seconds. Create the directory if it doesn't exist yet. A new date does not overwrite the existing date in the file but appends it.

Show Solution 

if [ ! -d ~/tmp ]; then mkdir -p ~/tmp; fi; while true; do echo $(date) >> ~/tmp/date.txt; sleep 5; done;

Printing a counter to the console

Write a bash one-liner that defines a variable counter with the initial value 0. Increment the variable every second and print out its value to the console.

Show Solution 

counter=0; while true; do counter=$((counter+1)); echo "$counter"; sleep 1; done;

Creating a random number

Write a bash one-liner that defines a variable with a value between 1 and 100. In a loop, print the value of the variable if it is less than 50. Break the loop if the value is more or equal to 50 and print out the message "END: $value".

Show Solution 

while true; do random=$(((RANDOM % 100) + 1)); if [ $random -le 50 ]; then echo "$random"; else echo "END: $random"; break; fi; sleep 1; done;

Kubernetes Object Information

Finding specific annotations

Print the sourrounding 10 lines of Pod description for any existing Pod with the annotation author=John Doe.

Show Solution 

kubectl describe pods | grep -C 10 "author=John Doe"

Finding all labels

Print labels for all Pods and determine their Pod names. Render the output in YAML format.

Show Solution 

kubectl get pods -o yaml | grep -C 5 labels: