CKAD — K8s imperative commands (cheatsheet)

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Abbreviations

  • po — pods, pod
  • deploy — deployments, deployment
  • netpol — networkpolicy
  • rs — replicaset, replicasets
  • cj — cronjob
  • pv — persistent volume
  • pvc — persistent volume claim

Setting up alias and autocompletion with alias

alias k=kubectl

View current context

kubectl config current-context

Core Concepts

Set image of pod nginx : image name is nginx and correct value is nginx

k set image po nginx nginx=nginx

Force delete a pod

K delete po nains -n mynamespace — grace-period=0 — force

Verbosity level of information: level — v=0 till — v=9

k get po nginxtag — v=9

Get custom columns in pod summary. Notation is similar to jsonpath notation. File can also be used with custom-columns-file

kubectl get po -o=custom-columns=”POD_NAME:.metadata.name, POD_STATUS:.status.containerStatuses[].state”

Get pod field details using jsonpath notation. File can also be used with jsonpath-file

K get po -o=jsonpath=“$.spec.containers[].name”

Sort pod summary by name

k get po — sort-by=”{.metadata.name}”

Sort pod summary by timestamp

k get po — sort-by=.metadata.creationTimestamp

Logging and Debugging

Get log dump of a pod

k logs

Tail logs of a pod or follow logs

k logs -f

Get logs of a container in multi container pod

k logs -c

Get previous logs of a container

k logs -c — p

Node and pod meterics. Below commands only run if metric server is installed.

k top po nginx — containers k top node node01

Labels and selectors

Get pods summary with labels

k get po — show-labels

Get node summary with labels

k get nodes — show-labels

Create a pod using container image nginx and add label while creation

k run po nginx — image=nginx — labels=env=prod

Another way to add label during pod creation using -l

k run nginx — image=nginx -l env=prod

Filter pods with specific label name. Get pods with label env=prod

k get po -l env=prod OR k get po — selector=env=prod OR k get po — show-labels -l env=prod OR k get po — selector=env=dev — show-labels

Get pods with label whose key name is ‘env’

k get po -l env

How all pods with label env. There should be 1 column name ‘env’ with corresponding values under it for each pod.

k get po -L env

Filter pod with more than 1 label values. Get pods with env = prod and env=dev

k get po — show-labels -l ‘env in (dev,prod)’

Update a label value

k label po ng1 env=uat — overwrite

Removing a label. Note hyphen at end

k label po ng3 env-

Add label to sequentially named pods in same command

k label po ng{1..3} app=nginx

Label an existing node

k label node controlplane labelname=labelvalue

Get taint on a node

k describe node controlplane | grep -A3 Taint # grep 3 lines after match

Annotate a pod. Similar syntax to label.

k annotate po nginx name=webapp

Verify pod annoation.

k describe po nginx | grep -i -A3 annotation

Remove an annotation

k annotate po nginx name-

Delete all pods

k delete po — all # delete all pods

Get all pods across all namespaces

K get all — all-namespaces OR K get all -A

Get all pods in a specific namespace

K get all -n mynamespace OR K get all — namespace=mynamespace

Deployments

Create deployment with a pod with image as nginx. Replicas = 5

k create deploy webapp — image=nginx — replicas=5

To get pods of a deployment can fetch by label of deployment

k get po — show-labels -l app=webapp

Upscale / downscale an existing deployment

k scale deploy webapp — replicas=20

To get replicates linked with deployment get rs with same label as deployment

k get rs -l app=webapp

To watch a pod creation in action use -w to watch

k get po -w

Update image in an existing deployment

kubectl set image deploy webapp nginx=nginx:1.17.4

Update image and record the command so that it is visible under ‘Cause’ field in rollout history

kubectl set image deploy webapp nginx=nginx:1.17.4 — record=true

Undo a deployment

k rollout undo deploy webapp

Undo a deployment to a specific revision number

k rollout undo deploy webapp — to-revision=1

Get rollout history of a deployment

kubectl rollout history deploy webap

Get history of a specific rollout revision

kubectl rollout history deploy webapp — revision=7

Pause a rollout

k rollout pause deploy webapp

Resumes any stuck image update which was paused due to pause command issued earlier

k rollout resume deploy webapp

Deployment rollout status

k rollout status deploy webapp

HPA — horizontal pod autoscaler

k get hpa

Jobs and Cronjobs

Create a job which runs a command to verify node version

k create job myjob — image=node — /bin/sh -c “node -v”

Delete all jobs

k delete job — all

watch jobs summary

k get jobs -w

Create cronjob with a scheduled run of every minute

k create cronjob cjob — image=busybox — schedule=”*/1 * * * *” — /bin/sh -c “date;echo ‘hello’”

Get info on command usage

Which fields are under spec section of pod in yaml

k explain po.spec — recursive | less

Config Map

To see all example usages of config map create command

k create cm — help

Verify env variables of pod

k exec -it nginx — env

Verify Security Context of a container

kubectl exec -it secbusybox — sh id // it will show the id and group

Secret

k create secret generic mysecret — from-literal=key1=value1

Decode a secret

echo -n bXlwYXNzd29yZA== | base64 — decode

Encode a secret

echo -n mypassword | base64

Edit base64 value in secret

k edit secret mysecret

Get events of a pod, -o wide, sorted by timestamp

k get events -o wide — sort-by=.metadata.creationTimestamp — field-selector involvedObject.name=busybox

Write above summary into a txt file

k get events -o wide — sort-by=.metadata.creationTimestamp — field-selector involvedObject.name=busybox > temp.txt

Get all pod events into a file sorted by timestamp

k get events — sort-by=.metadata.creationTimestamp > bb.txt

Get pods with sorted cpu usage descending order and write top 3 entries to a text file

kubectl top pod — all-namespaces | sort — reverse — key 3 — numeric | head -3 > cpu-usage.txt OR kubectl top pod — all-namespaces | sort -nrk 3 | head -3 > a.txt

Service

Check usages of expose command

k expose — help

Execute shell in a container when pod has 2 containers

k exec -it 2c -c 2c-b -n ggckad-s2 — sh

Resource Quota

Create resource quota

kubectl create quota my-quota — hard=cpu=1,memory=1G,pods=2,services=3,replicationcontrollers=2,resourcequotas=1,secrets=5,persistentvolumeclaims=10

Create pod and set env variables during creation

kubectl run hazelcast — image=hazelcast/hazelcast — env=”DNS_DOMAIN=cluster” — env=”POD_NAMESPACE=default”

Specify POD resource request and limit during pod creation

k run ng8 — image=nginx — limits=cpu=200m,memory=512Mi — requests=cpu=100m,memory=256Mi

Copy from pod folder to local folder

k cp :etc/passwd ./pwd

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