The awesome of Kubectl snippet

Info

Small script and take a note to interact between kubectl and your kubernetes cluster.

You can explore command with kubectl in some place, including

• kubectl Quick Reference
• kubectl reference

Combination

Force terminate the stuck namespace

NS=`kubectl get ns |grep Terminating | awk 'NR==1 {print $1}'` && kubectl get namespace "$NS" -o json   | tr -d "\n" | sed "s/\"finalizers\": \[[^]]\+\]/\"finalizers\": []/"   | kubectl replace --raw /api/v1/namespaces/$NS/finalize -f - 

Config Command

Check currently config context

kubectl config view --minify

Create Command

Create the generic secrets from file

For example binary file with auto convert to base64 format

kubectl create secret generic accounts-identityserver-certificate --from-file=certificate.pfx --dry-run=client -o yaml > certificate_sec.yaml 

Debug Command

Debug your node via kubectl

kubectl debug node/my-node -it --image=<img>

Delete command

Delete all component inside cluster

# For example: Delete all pvc in namespace default
kubectl delete pvc --all 

Delete pods with not on state Running

k delete pods -n <name-space> --field-selector=status.phase!=Running

External command

Check the resource of workload v1

Download via krew, find out the step at krew installing and extension at github

kubectl krew install resource-capacity

# Extension: https://github.com/robscott/kube-capacity
 
# Check the available resources
kubectl resource-capacity -a
 
# Check detail resource utilize of all workload
kubectl resource-capacity -p --util

Check the resource of workload, able to view GPU

Download new extension from krew at github

kubectl krew install view-allocations

# Extension: https://github.com/davidB/kubectl-view-allocations
 
# Show GPU allocation
k view-allocation -r gpu
 
# Check available resource of all node
k view-allocation -g resource
 
# Check resource depend on group namespace
k view-allocation -g namespace
 
# View as csv for analysis
k view-allocations -o csv

View relationship between resources

Download new extension from krew at github

kubectl krew install tree

# Extension: https://github.com/ahmetb/kubectl-tree
 
# View relationship of deployment
k tree deployment <name-deploymen>
 
# You can view the resource with API. e.g: longhorn share manager
k tree sharemanagers.longhorn.io test

Spawn node-shell for debug node

Down new extension from krew at github

kubectl krew install node-shell

# Extension: https://github.com/kvaps/kubectl-node-shell
 
# Get standard bash shell
kubectl node-shell <node>
 
# Use custom image for pod
kubectl node-shell <node> --image <image>
 
# Execute custom command
kubectl node-shell <node> -- echo 123
 
# Use stdin
cat /etc/passwd | kubectl node-shell <node> -- sh -c 'cat > /tmp/passwd'
 
# Run oneliner script
kubectl node-shell <node> -- sh -c 'cat /tmp/passwd; rm -f /tmp/passwd'

Get Command

Base64 decode of secret with no more 3th party

# Use go-template
kubectl get secrets -n <namespace> <secret> \
-o go-template='{{range $k,$v := .data}}{{"### "}}{{$k}}{{"\n"}}{{$v|base64decode}}{{"\n\n"}}{{end}}'
 
# Use json
kubectl get secret -n <namespace> <secret> -o jsonpath='{.data.*}' | base64 -d

Get events with filter depend creationTimestamp

kubectl get events -n <namespace> --sort-by=.metadata.creationTimestamp

Get taint of node

kubectl get nodes -o='custom-columns=NodeName:.metadata.name,TaintKey:.spec.taints[*].key,TaintValue:.spec.taints[*].value,TaintEffect:.spec.taints[*].effect'

Patch Command

Change default storage class for your node

kubectl patch storageclass <sc-specific> -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'

Rollout Command

Read more about rollout at: How do you rollback deployments in Kubernetes?

Roll out the previous deployment

# Check history of version
# View history tree of your application
kubectl rollout history deployment <deployment-name> -n <namespace>
# View detail once of history of your revision
kubectl rollout history deployment <deployment-name> \
-n <namespace> --revision <revision_number>
 
# Rollout to version
# Rollout your application to 0 (last revision). Default
kubectl rollout undo deployment <deployment-name> -n <namespace>
# Rollout your application to specific revision
kubectl rollout undo deployment <deployment-name> \
-n <namespace> --to-revision <revision_number>

Scale Command

Scale down the statefulset application

# Use scale option
kubectl scale --replicas=0 sts <sts name>
 
# Or we can use patch or edit option
kubectl patch statefulsets <stateful-set-name> -p '{"spec":{"replicas":<new-replicas>}}'

Note

You need to consider when apply scaling down can not working because “cannot scale down a StatefulSet when any of the stateful Pods it manages is unhealthy. Scaling down only takes place after those stateful Pods become running and ready.” . Read more in: Scale a StatefulSet