kubectl cheat sheet

Run from support01 with ~/.kube/config in place (Lab 01). No sudo.

Setup that saves hours

alias k=kubectl
source <(kubectl completion bash)
complete -o default -F __start_kubectl k
export do="--dry-run=client -o yaml"      # then: kubectl run x --image=nginx $do
kubectl config set-context --current --namespace=dev

Ask the cluster instead of the internet

Question	Command
Which kinds exist? short names? namespaced?	`kubectl api-resources`
Which kinds are cluster-scoped?	`kubectl api-resources --namespaced=false`
Which fields does this kind have?	`kubectl explain ingress.spec.rules`
All fields at once	`kubectl explain deploy.spec --recursive`
What can this command do?	`kubectl create --help` (examples at the bottom)
Global flags	`kubectl options`
Client / server version	`kubectl version`
Can I do this?	`kubectl auth can-i create deployments -n dev`

Look around

Task	Command
Cluster reachable?	`kubectl cluster-info`
Nodes with IPs and versions	`kubectl get nodes -o wide`
Everything in a namespace	`kubectl get all -n dev`
All namespaces	`kubectl get pods -A`
Watch changes live	`kubectl get pods -w`
Sorted events	`kubectl get events --sort-by=.lastTimestamp`
Warnings only, everywhere	`kubectl get events -A --field-selector type=Warning`
Resource usage	`kubectl top nodes` / `kubectl top pods`
By label	`kubectl get pods -l app=web`
Custom columns	`kubectl get pods -o custom-columns=NAME:.metadata.name,NODE:.spec.nodeName`

Create and change

Task	Command
Apply a manifest (or a dir)	`kubectl apply -f pod.yaml` / `-f ./manifests/`
Generate YAML without creating	`kubectl run web --image nginx --dry-run=client -o yaml > web.yaml`
Deployment YAML	`kubectl create deploy web --image nginx --dry-run=client -o yaml`
Service for a deployment	`kubectl expose deploy web --port 80 --type NodePort`
Ingress (legacy)	`kubectl create ingress web --rule="web.k8s.lab/*=web-svc:80"`
Edit a live object	`kubectl edit deploy web`
Patch a field	`kubectl patch svc web -p '{"spec":{"type":"NodePort"}}'`
Scale	`kubectl scale deploy web --replicas=3`
Change an image	`kubectl set image deploy/web nginx=nginx:1.28`
Env from a ConfigMap	`kubectl set env deploy/web --from=configmap/app-cfg`
Label / annotate	`kubectl label pod web tier=frontend`
Delete	`kubectl delete -f web.yaml` / `kubectl delete pod web`

Inspect and debug

Task	Command
Everything about an object + events	`kubectl describe pod web`
Live object as YAML	`kubectl get pod web -o yaml`
One field	`kubectl get pod web -o jsonpath='{.status.podIP}'`
Logs, follow, previous crash	`kubectl logs -f web` / `kubectl logs web --previous`
Logs of one container	`kubectl logs web -c sidecar`
Logs by label / via controller	`kubectl logs -l app=web --tail=50` / `kubectl logs deploy/web`
Shell inside	`kubectl exec -it web -- sh`
Throwaway debug Pod	`kubectl run tmp --image busybox --restart=Never -it --rm -- sh`
Port-forward	`kubectl port-forward svc/web 8080:80`
Copy files	`kubectl cp web:/etc/nginx/nginx.conf ./nginx.conf`
Service endpoints	`kubectl get endpointslices -l kubernetes.io/service-name=web`

Workloads

kubectl rollout status  deploy/web
kubectl rollout history deploy/web
kubectl rollout undo    deploy/web
kubectl rollout restart deploy/web
kubectl get rs -l app=web              # which ReplicaSet is active
kubectl get ds -A                      # DaemonSets
kubectl get sts                        # StatefulSets

Storage

kubectl get pv                                   # cluster-scoped
kubectl get pvc -A
kubectl describe pvc data                        # why is it Pending?
kubectl get sc                                   # StorageClasses
kubectl get csidrivers                           # installed CSI drivers
kubectl get pv -o custom-columns=NAME:.metadata.name,STATUS:.status.phase,CLAIM:.spec.claimRef.name,POLICY:.spec.persistentVolumeReclaimPolicy
kubectl patch pv <pv> -p '{"spec":{"claimRef":null}}'   # reuse a Released PV

Gateway API

kubectl get gatewayclass
kubectl get gateway,httproute -A
kubectl describe gateway web-gw          # PROGRAMMED + conditions
kubectl describe httproute shop          # Accepted + ResolvedRefs
kubectl explain httproute.spec.rules.backendRefs

The CRDs must be installed first - Gateway API is not part of Kubernetes.

Custom resources

kubectl get crd
kubectl api-resources --api-group=postgresql.cnpg.io
kubectl explain cluster.spec
kubectl get clusters -A

Nodes

kubectl cordon   worker01
kubectl drain    worker01 --ignore-daemonsets --delete-emptydir-data
kubectl uncordon worker01
kubectl describe node worker01 | grep -A6 'Allocated resources'

Short names

po pods, deploy deployments, rs replicasets, svc services, ing ingresses, ds daemonsets, sts statefulsets, ns namespaces, cm configmaps, no nodes, gtw gateways, httproute httproutes, pv/pvc volumes, sa serviceaccounts, crd customresourcedefinitions.

Reference

kubernetes.io/docs/reference/kubectl/quick-reference