CKAD — K8s imperative commands (cheatsheet)
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
source <(kubectl completion bash | sed ‘s/kubectl/k/g’)
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
k delete hpa
k autoscale deploy webapp — min=10 — max=20 — cpu-percent=85
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
k explain pv.spec. — recursive | grep -i -A10 hostpath hostPath path type
k get po — help
Config Map
To see all example usages of config map create command
k create cm — help
k create cm — from-literal=key1=value1
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
Please note, keeping a bookmark of k8s official documentation resources is allowed and comes very handy. I have created a bookmark file that can be downloaded and imported for easy reference.
