Kubernetes_Troubleshooting_Information.md

Kubernetes Troubleshooting Information

Commands for performing basic Kubernetes cluster troubleshooting.

• Access pod logs
• Describe a node
• Describe a pod
• Open a shell on a pod
• Run a single command on a pod
• Connect to a running container
• Scale a deployment
• Remove a deployment with the manifest and reapply the deployment
• Delete a pod

Access pod logs

(ncn-mw#) Use one of the following commands to retrieve pod-related logs:

kubectl logs POD_NAME

kubectl logs POD_NAME -c CONTAINER_NAME

(ncn-mw#) If the pods keeps crashing, open a log for the previous instance using the following command:

kubectl logs -p POD_NAME

Describe a node

(ncn-mw#) Use the following command to retrieve information about a node's condition, such as OutOfDisk, MemoryPressure, DiskPressure, etc.

kubectl describe node NODE_NAME

Describe a pod

(ncn-mw#) Use the following command to retrieve information that can help debug pod-related errors.

kubectl describe pod POD_NAME

(ncn-mw#) Use the following command to list all of the containers in a pod, as shown in the following example:

kubectl describe pod/cray-tftp-6f85767d76-b28gc -n default

Open a shell on a pod

(ncn-mw#) Use the following command to connect to a pod:

kubectl exec -it POD_NAME -c CONTAINER_NAME /bin/sh

Run a single command on a pod

(ncn-mw#) Use the following command to execute a command inside a pod:

kubectl exec POD_NAME ls /

Connect to a running container

(ncn-mw#) Use the following command to connect to a currently running container:

kubectl attach POD_NAME -i

Scale a deployment

(ncn-mw#) Use the deployment command to scale a deployment up or down, as shown in the following examples:

kubectl scale deployment APPLICATION_NAME --replicas=0
kubectl scale deployment APPLICATION_NAME --replicas=3

Remove a deployment with the manifest and reapply the deployment

(ncn-mw#) Use the following command to remove components of the deployment's manifest, such as services, network policies, and more:

kubectl delete –f APPLICATION_NAME.yaml

(ncn-mw#) Use the following command to reapply the deployment:

kubectl apply –f APPLICATION_NAME.yaml

Delete a pod

(ncn-mw#) Pods can be configured to restart after getting deleted. Use the following command to delete a pod:

kubectl delete pod POD_NAME

CAUTION: It is recommended to be careful while deleting deployments or pods, because doing so can have an effect on other pods.