3 - Pod design

Question 1

Create 3 pods with names nginx1,nginx2,nginx3. All of them should have the label app=v1

Answer 1

for i in seq 1 3; do kubectl run nginx$i –image=nginx -l app=v1 ; done

Question 2

Show all labels of the pods

Answer 2

kubectl get po –show-labels

Question 3

Change the labels of pod ‘nginx2’ to be app=v2

Answer 3

kubectl label po nginx2 app=v2 –overwrite

Question 4

Get the label ‘app’ for the pods (show a column with APP labels)

Answer 4

kubectl get po -L app
# or
kubectl get po –label-columns=app

Question 5

Get only the ‘app=v2’ pods

Answer 5

kubectl get po -l app=v2
# or
kubectl get po -l ‘app in (v2)’
# or
kubectl get po –selector=app=v2

Question 6

Add a new label tier=web to all pods having ‘app=v2’ or ‘app=v1’ labels

Answer 6

kubectl label po -l “app in(v1,v2)” tier=web

Question 7

Add an annotation ‘owner: marketing’ to all pods having ‘app=v2’ label

Answer 7

kubectl annotate po -l “app=v2” owner=marketing

Question 8

Remove the ‘app’ label from the pods we created before

Answer 8

kubectl label po nginx1 nginx2 nginx3 app-
# or
kubectl label po nginx{1..3} app-
# or
kubectl label po -l app app-

Question 9

Annotate pods nginx1, nginx2, nginx3 with “description=’my description’” value

Answer 9

or

kubectl annotate po nginx1 nginx2 nginx3 description=’my description’

kubectl annotate po nginx{1..3} description=’my description’

Question 10

Check the annotations for pod nginx1

Answer 10

kubectl annotate pod nginx1 –list

or

kubectl describe po nginx1 | grep -i ‘annotations’

or

kubectl get po nginx1 -o custom-columns=Name:metadata.name,ANNOTATIONS:metadata.annotations.description

Question 11

Remove the annotations for these three pods

Answer 11

kubectl annotate po nginx{1..3} description- owner-

Question 12

Remove these pods to have a clean state in your cluster

Answer 12

kubectl delete po nginx{1..3}

Question 13

Create a pod that will be deployed to a Node that has the label ‘accelerator=nvidia-tesla-p100’

Answer 13

kubectl label nodes <your-node-name> accelerator=nvidia-tesla-p100
kubectl get nodes --show-labels</your-node-name>

apiVersion: v1
kind: Pod
metadata:
name: cuda-test
spec:
containers:
- name: cuda-test
image: “k8s.gcr.io/cuda-vector-add:v0.1”
nodeSelector: # add this
accelerator: nvidia-tesla-p100 # the selection label

kubectl explain po.spec

apiVersion: v1
kind: Pod
metadata:
name: affinity-pod
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: accelerator
operator: In
values:
- nvidia-tesla-p100
containers:
…

Question 14

Taint a node with key tier and value frontend with the effect NoSchedule. Then, create a pod that tolerates this taint.

Answer 14

kubectl taint node node1 tier=frontend:NoSchedule # key=value:Effect
kubectl describe node node1 # view the taints on a node

apiVersion: v1
kind: Pod
metadata:
name: frontend
spec:
containers:
- name: nginx
image: nginx
tolerations:
- key: “tier”
operator: “Equal”
value: “frontend”
effect: “NoSchedule”

Question 15

Create a pod that will be placed on node controlplane. Use nodeSelector and tolerations.

Answer 15

apiVersion: v1
kind: Pod
metadata:
name: frontend
spec:
containers:
- name: nginx
image: nginx
nodeSelector:
kubernetes.io/hostname: controlplane
tolerations:
- key: “node-role.kubernetes.io/control-plane”
operator: “Exists”
effect: “NoSchedule”

Question 16

Create a deployment with image nginx:1.18.0, called nginx, having 2 replicas, defining port 80 as the port that this container exposes (don’t create a service for this deployment)

Answer 16

change the replicas field from 1 to 2

kubectl create deployment nginx –image=nginx:1.18.0 –dry-run=client -o yaml > deploy.yaml
vi deploy.yaml
# add this section to the container spec and save the deploy.yaml file
# ports:
# - containerPort: 80
kubectl apply -f deploy.yaml

kubectl create deploy nginx –image=nginx:1.18.0 –replicas=2 –port=80

Question 17

View the YAML of this deployment

Answer 17

kubectl get deploy nginx -o yaml

Question 18

View the YAML of the replica set that was created by this deployment

Answer 18

kubectl describe deploy nginx # you’ll see the name of the replica set on the Events section and in the ‘NewReplicaSet’ property
# OR you can find rs directly by:
kubectl get rs -l run=nginx # if you created deployment by ‘run’ command
kubectl get rs -l app=nginx # if you created deployment by ‘create’ command
# you could also just do kubectl get rs
kubectl get rs nginx-7bf7478b77 -o yaml

Question 19

Get the YAML for one of the pods

Answer 19

kubectl get po # get all the pods
# OR you can find pods directly by:
kubectl get po -l run=nginx # if you created deployment by ‘run’ command
kubectl get po -l app=nginx # if you created deployment by ‘create’ command
kubectl get po nginx-7bf7478b77-gjzp8 -o yaml

Question 20

Check how the deployment rollout is going

Answer 20

kubectl rollout status deploy nginx

Question 21

Update the nginx image to nginx:1.19.8

Answer 21

kubectl set image deploy nginx nginx=nginx:1.19.8
# alternatively…
kubectl edit deploy nginx # change the .spec.template.spec.containers[0].image

Question 22

Check the rollout history and confirm that the replicas are OK

Answer 22

kubectl rollout history deploy nginx
kubectl get deploy nginx
kubectl get rs # check that a new replica set has been created
kubectl get po

Question 23

Undo the latest rollout and verify that new pods have the old image (nginx:1.18.0)

Answer 23

kubectl rollout undo deploy nginx
# wait a bit
kubectl get po # select one ‘Running’ Pod
kubectl describe po nginx-5ff4457d65-nslcl | grep -i image # should be nginx:1.18.0

Question 24

Do an on purpose update of the deployment with a wrong image nginx:1.91

Answer 24

kubectl set image deploy nginx nginx=nginx:1.91
# or
kubectl edit deploy nginx
# change the image to nginx:1.91
# vim tip: type (without quotes) ‘/image’ and Enter, to navigate quickly

Question 25

Verify that something’s wrong with the rollout

Answer 25

kubectl rollout status deploy nginx
# or
kubectl get po # you’ll see ‘ErrImagePull’ or ‘ImagePullBackOff’

Question 26

Return the deployment to the second revision (number 2) and verify the image is nginx:1.19.8

Answer 26

kubectl rollout undo deploy nginx –to-revision=2
kubectl describe deploy nginx | grep Image:
kubectl rollout status deploy nginx # Everything should be OK

Question 27

Check the details of the fourth revision (number 4)

Answer 27

kubectl rollout history deploy nginx –revision=4 # You’ll also see the wrong image displayed here

Question 28

Scale the deployment to 5 replicas

Answer 28

kubectl scale deploy nginx –replicas=5
kubectl get po
kubectl describe deploy nginx

Question 29

Autoscale the deployment, pods between 5 and 10, targetting CPU utilization at 80%

Answer 29

kubectl autoscale deploy nginx –min=5 –max=10 –cpu-percent=80
# view the horizontalpodautoscalers.autoscaling for nginx
kubectl get hpa nginx

Question 30

Pause the rollout of the deployment

Answer 30

kubectl rollout pause deploy nginx

Question 31

Update the image to nginx:1.19.9 and check that there’s nothing going on, since we paused the rollout

Answer 31

kubectl set image deploy nginx nginx=nginx:1.19.9
# or
kubectl edit deploy nginx
# change the image to nginx:1.19.9
kubectl rollout history deploy nginx # no new revision

Question 32

Resume the rollout and check that the nginx:1.19.9 image has been applied

Answer 32

kubectl rollout resume deploy nginx
kubectl rollout history deploy nginx
kubectl rollout history deploy nginx –revision=6 # insert the number of your latest revision

Question 33

Delete the deployment and the horizontal pod autoscaler you created

Answer 33

Or

kubectl delete deploy nginx
kubectl delete hpa nginx

kubectl delete deploy/nginx hpa/nginx

Question 34

Implement canary deployment by running two instances of nginx marked as version=v1 and version=v2 so that the load is balanced at 75%-25% ratio

Answer 34

apiVersion: apps/v1
kind: Deployment
metadata:
name: my-app-v1
labels:
app: my-app
spec:
replicas: 3
selector:
matchLabels:
app: my-app
version: v1
template:
metadata:
labels:
app: my-app
version: v1
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 80
volumeMounts:
- name: workdir
mountPath: /usr/share/nginx/html
initContainers:
- name: install
image: busybox:1.28
command:
- /bin/sh
- -c
- “echo version-1 > /work-dir/index.html”
volumeMounts:
- name: workdir
mountPath: “/work-dir”
volumes:
- name: workdir
emptyDir: {}

run a wget to the Service my-app-svc
kubectl run -it –rm –restart=Never busybox –image=gcr.io/google-containers/busybox –command – wget -qO- my-app-svc

version-1

kubectl scale –replicas=4 deploy my-app-v2
kubectl delete deploy my-app-v1
while sleep 0.1; do curl $(kubectl get svc my-app-svc -o jsonpath=”{.spec.clusterIP}”); done
version-2
version-2
version-2
version-2
version-2
version-2

Question 35

Create a job named pi with image perl:5.34 that runs the command with arguments “perl -Mbignum=bpi -wle ‘print bpi(2000)’”

Answer 35

kubectl create job pi –image=perl:5.34 – perl -Mbignum=bpi -wle ‘print bpi(2000)’

Question 36

Wait till it’s done, get the output

Answer 36

kubectl get jobs -w # wait till ‘SUCCESSFUL’ is 1 (will take some time, perl image might be big)
kubectl get po # get the pod name
kubectl logs pi-** # get the pi numbers
kubectl delete job pi

Question 37

Create a job with the image busybox that executes the command ‘echo hello;sleep 30;echo world’

Answer 37

kubectl create job busybox –image=busybox – /bin/sh -c ‘echo hello;sleep 30;echo world’

Question 38

Follow the logs for the pod (you’ll wait for 30 seconds)

Answer 38

kubectl get po # find the job pod
kubectl logs busybox-ptx58 -f # follow the logs

Question 39

See the status of the job, describe it and see the logs

Answer 39

kubectl get jobs
kubectl describe jobs busybox
kubectl logs job/busybox

Question 40

Delete the job

Answer 40

kubectl delete job busybox

Question 41

Create a job but ensure that it will be automatically terminated by kubernetes if it takes more than 30 seconds to execute

Answer 41

kubectl create job busybox –image=busybox –dry-run=client -o yaml – /bin/sh -c ‘while true; do echo hello; sleep 10;done’ > job.yaml
vi job.yaml
Add job.spec.activeDeadlineSeconds=30

apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
labels:
run: busybox
name: busybox
spec:
activeDeadlineSeconds: 30 # add this line
template:
metadata:
creationTimestamp: null
labels:
run: busybox
spec:
containers:
- args:
- /bin/sh
- -c
- while true; do echo hello; sleep 10;done
image: busybox
name: busybox
resources: {}
restartPolicy: OnFailure
status: {}

Question 42

Create the same job, make it run 5 times, one after the other. Verify its status and delete it

Answer 42

kubectl create job busybox –image=busybox –dry-run=client -o yaml – /bin/sh -c ‘echo hello;sleep 30;echo world’ > job.yaml
vi job.yaml
Add job.spec.completions=5

apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
labels:
run: busybox
name: busybox
spec:
completions: 5 # add this line
template:
metadata:
creationTimestamp: null
labels:
run: busybox
spec:
containers:
- args:
- /bin/sh
- -c
- echo hello;sleep 30;echo world
image: busybox
name: busybox
resources: {}
restartPolicy: OnFailure
status: {}
kubectl create -f job.yaml
Verify that it has been completed:

kubectl get job busybox -w # will take two and a half minutes
kubectl delete jobs busybox

Question 43

Create the same job, but make it run 5 parallel times

Answer 43

vi job.yaml
Add job.spec.parallelism=5

apiVersion: batch/v1
kind: Job
metadata:
creationTimestamp: null
labels:
run: busybox
name: busybox
spec:
parallelism: 5 # add this line
template:
metadata:
creationTimestamp: null
labels:
run: busybox
spec:
containers:
- args:
- /bin/sh
- -c
- echo hello;sleep 30;echo world
image: busybox
name: busybox
resources: {}
restartPolicy: OnFailure
status: {}
kubectl create -f job.yaml
kubectl get jobs
It will take some time for the parallel jobs to finish (>= 30 seconds)

kubectl delete job busybox

Question 44

Create a cron job with image busybox that runs on a schedule of “*/1 * * * *” and writes ‘date; echo Hello from the Kubernetes cluster’ to standard output

Answer 44

kubectl create cronjob busybox –image=busybox –schedule=”*/1 * * * *” – /bin/sh -c ‘date; echo Hello from the Kubernetes cluster’

Question 45

See its logs and delete it

Answer 45

kubectl get po # copy the ID of the pod whose container was just created
kubectl logs <busybox-***> # you will see the date and message
kubectl delete cj busybox # cj stands for cronjob

Question 46

Create the same cron job again, and watch the status. Once it ran, check which job ran by the created cron job. Check the log, and delete the cron job

Answer 46

kubectl get cj
kubectl get jobs –watch
kubectl get po –show-labels # observe that the pods have a label that mentions their ‘parent’ job
kubectl logs busybox-1529745840-m867r
# Bear in mind that Kubernetes will run a new job/pod for each new cron job
kubectl delete cj busybox

Question 47

Create a cron job with image busybox that runs every minute and writes ‘date; echo Hello from the Kubernetes cluster’ to standard output. The cron job should be terminated if it takes more than 17 seconds to start execution after its scheduled time (i.e. the job missed its scheduled time).

Answer 47

kubectl create cronjob time-limited-job –image=busybox –restart=Never –dry-run=client –schedule=”* * * * *” -o yaml – /bin/sh -c ‘date; echo Hello from the Kubernetes cluster’ > time-limited-job.yaml
vi time-limited-job.yaml
Add cronjob.spec.startingDeadlineSeconds=17

apiVersion: batch/v1
kind: CronJob
metadata:
creationTimestamp: null
name: time-limited-job
spec:
startingDeadlineSeconds: 17 # add this line
jobTemplate:
metadata:
creationTimestamp: null
name: time-limited-job
spec:
template:
metadata:
creationTimestamp: null
spec:
containers:
- args:
- /bin/sh
- -c
- date; echo Hello from the Kubernetes cluster
image: busybox
name: time-limited-job
resources: {}
restartPolicy: Never
schedule: ‘* * * * *’
status: {}

Question 48

Create a cron job with image busybox that runs every minute and writes ‘date; echo Hello from the Kubernetes cluster’ to standard output. The cron job should be terminated if it successfully starts but takes more than 12 seconds to complete execution.

Answer 48

kubectl create cronjob time-limited-job –image=busybox –restart=Never –dry-run=client –schedule=”* * * * *” -o yaml – /bin/sh -c ‘date; echo Hello from the Kubernetes cluster’ > time-limited-job.yaml
vi time-limited-job.yaml
Add cronjob.spec.jobTemplate.spec.activeDeadlineSeconds=12

apiVersion: batch/v1
kind: CronJob
metadata:
creationTimestamp: null
name: time-limited-job
spec:
jobTemplate:
metadata:
creationTimestamp: null
name: time-limited-job
spec:
activeDeadlineSeconds: 12 # add this line
template:
metadata:
creationTimestamp: null
spec:
containers:
- args:
- /bin/sh
- -c
- date; echo Hello from the Kubernetes cluster
image: busybox
name: time-limited-job
resources: {}
restartPolicy: Never
schedule: ‘* * * * *’
status: {}

Question 49

Create a job from cronjob.

Answer 49

kubectl create job –from=cronjob/sample-cron-job sample-job