Kubernetes Cheatsheet

Common Commands

Cluster Management

• kubectl get nodes - List all nodes
• kubectl get pods -A - List all pods in all namespaces
• kubectl get events -A - View cluster events

Debugging

• kubectl describe pod <pod-name> - Get detailed pod information
• kubectl logs <pod-name> - View pod logs
• kubectl exec -it <pod-name> -- /bin/bash - Execute command in pod

Resource Management

• kubectl top nodes - View node resource usage
• kubectl top pods - View pod resource usage
• kubectl get pvc - List persistent volume claims

Troubleshooting Tips

Node Issues

• Check kubelet status: systemctl status kubelet
• Check disk space: df -h
• Check memory usage: free -h

Pod Issues

• Check pod events: kubectl describe pod <pod-name>
• Check pod logs: kubectl logs <pod-name> --previous (for previous instance)
• Check resource limits: kubectl describe pod <pod-name> | grep -i limit

Network Issues

• Test connectivity: kubectl exec <pod-name> -- ping <target>
• Check DNS resolution: kubectl exec <pod-name> -- nslookup <service>
• Check service endpoints: kubectl get endpoints <service-name>

Commands

• Get resources

$ kubectl api-resources --api-group ""
NAME                     SHORTNAMES   APIVERSION   NAMESPACED   KIND
bindings                              v1           true         Binding
componentstatuses        cs           v1           false        ComponentStatus
configmaps               cm           v1           true         ConfigMap
endpoints                ep           v1           true         Endpoints
events                   ev           v1           true         Event
limitranges              limits       v1           true         LimitRange
namespaces               ns           v1           false        Namespace
nodes                    no           v1           false        Node
persistentvolumeclaims   pvc          v1           true         PersistentVolumeClaim
persistentvolumes        pv           v1           false        PersistentVolume
pods                     po           v1           true         Pod
podtemplates                          v1           true         PodTemplate
replicationcontrollers   rc           v1           true         ReplicationController
resourcequotas           quota        v1           true         ResourceQuota
secrets                               v1           true         Secret
serviceaccounts          sa           v1           true         ServiceAccount
services                 svc          v1           true         Service

Namespaces

• Namespaces are a way to divide cluster resources between multiple users.

• Namespaces cannot be nested.

• Create a namespace via declration. $ kubectl create namespace kubernetes_fail -oyaml --dry-run=client > namespace.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: kubernetes_fail
spec: {}
status: {}

• Create the namespace from file kubectl apply --from-file namespace.yaml
• kubectl get pod --all-namespaces Get all pods in all namespaces.

Debugging

• kubectl describe pod --namespace kubernetes-fail debug describe the pod debug in namespace kubernetes-fail, look for any errors.

  Normal   Pulled     95s                   kubelet            spec.containers{debug}: Successfully pulled image "cgr.dev/chainguard/busybox:latest" in 419ms (419ms including waiting). Image size: 3982143 bytes.
  Warning  Failed     95s                   kubelet            spec.containers{debug}: Error: failed to generate container "b1cce48c2bbfd3519eb476674b7e78aa6645f4dda02dddf8aa83f41c6da767f9" spec: failed to generate spec: no command specified

• kubectl logs --namespace kubernetes-fail debug get logs from pod debug in namespace kubernetes-fail

• Create a busybox pod in namespace, and enable interactive shell

cat pod-busybox.yaml 
apiVersion: v1
kind: Pod
metadata:
  labels:
    run: debug
  name: debug
  namespace: kubernetes-fail
spec:
  containers:
  - image: cgr.dev/chainguard/busybox:latest
    name: debug
    resources: {}
    args:
      - sh
    stdin: true
    tty: true
  dnsPolicy: ClusterFirst
  restartPolicy: Always
status: {}

• Attach to pod, kubectl attach --namespace kubernetes-fail debug -it

Deployments

• kubectl get deployments --namespace kubernetes-fail get deployments in namespace kubernetes-fail
• multiple resources can be created from a single file, by separating them with --- in the file, here the order matters, first create the namespace then the deployment and all its other resources.
• when appying multiple resources from files (eg: kubectl apply -f), the order matters.

Show all pods based on label

• kubectl get pods --all-namespaces --selector app=webserver List all pods with the label app=webserver
• kubectl get pods -A -l app=webserver Same in short.

Show pods with exta info

• kubectl get pods --output wide Show pods with extra info like IP address

Get ports of a pod

• kubectl exec -it webserver-1234567890-abcde -- netstat -tulpn Get open ports of a pod

create a loadbalancer with a persistent (cluster private) IP address

• kubectl create service clusterip webserver --tcp=8080 --namespace kubernetes-fail -oyaml --dry-run=client > service.yaml
• kubectl apply -f service.yaml
• kubectl get service,endpoints show services and its endpoints
• kubectl get svc show services
• kubectl describe svc webserver describe the details of the loadbalancer

Kubectl explain

• kubectl explain pods.spec.containers.livenessProbe show the documentation for a given resource
• kubectl explain pods.spec.containers.env show the documentation for continer environment variables