Previous: kubectl for CKAD - exercise 1 - run a pod

Getting Started with kubectl for CKAD exam

First things first

Put your mouse away, forget you have a touchpad and keep your hands on the keyboard.

Start your terminal, the adventure continues…

The situation with the CKAD and other CK* exams is that we need to be fast. The key to be fast when editing yaml files and applying them with kubectl apply is - don’t leave Vim. Yes, we can run kubectl apply, even kubectl replace right from inside Vim!

Scenario

A pod testpod is running in the cluster. We want to change some value in the pod, for example the pod name ‘testpod’ to ‘nginx’. Most fields in a pod manifest can’t be changed for a running pod, but we still can use the kubectl edit command and then replace the pod.

Start editing pod testpod in Vim

kubectl edit po testpod

Look up the name value (testpod), then jump right to it by searching in Vim from the top

/testp     # search downwards from the top, no need to write the whole word
Enter
n          # repeat search downwards as needed

Replace the name value - type it or copy & paste it from the task description

C          # 'C'lear (delete) everything from the cursor to the end of this line and start writing
nginx

write (save) the document to persist changes

ESC         # 'ESC'ape from INSERT mode 
:w          # 'w'rite (save) the document, file name is provided by kubectl edit

If we would quit Vim now, the pod would not get updated. We need to replace the edited pod with a new one - and we need to do it as fast as possible.

Watch the magic… again

run kubectl replace directly from inside Vim - delete the pod and create a new one

:!kubectl replace -f % --force --grace-period 0     # % references the current file name

If everything is fine with the yaml file, pod is deleted and a new pod is created

k get pods -o wide   # view pods, -o wide is optional, it shows more info about resources

Scenario continued

If there is an error and the pod has not been replaced, read the error, then simply press Enter to edit the yaml file and correct the error.

write (save) the document

ESC         # 'ESC'ape from INSERT mode 
:w          # 'w'rite (save) the document

Repeat replacing the pod directly from Vim using the previous command

:up arrow    # repeat to find the command :!kubectl replace -f % --force --grace-period 0
Enter

If everything is fine with the yaml file, pod is replaced

k get pods -o wide   # view pods, -o wide is optional, it shows more info about resources

Close the document / quit Vim

:q

Vim quits, closing the edited pod manifest.

Congratulations!

Practice these steps to make replacing running pods with kubectl directly from Vim second nature.

Next: kubectl for CKAD - exercise 3 - set env and replace pod