# Debug Pods

Debug PodsThis guide is to help users debug applications that are deployed into Kubernetes and not behaving correctly. This is not a guide for people who want to debug their cluster. For that you should check out this guide.Diagnosing the problemThe first step in troubleshooting is triage. What is the problem? Is it your Pods, your Replication Controller or your Service?Debugging PodsDebugging Replication ControllersDebugging ServicesDebugging PodsThe first step in debugging a Pod is taking a look at it. Check the current state of the Pod and recent events with the following command:kubectl describe pods ${POD_NAME} Look at the state of the containers in the pod. Are they all Running? Have there been recent restarts?Continue debugging depending on the state of the pods.My pod stays pendingIf a Pod is stuck in Pending it means that it can not be scheduled onto a node. Generally this is because there are insufficient resources of one type or another that prevent scheduling. Look at the output of the kubectl describe ... command above. There should be messages from the scheduler about why it can not schedule your pod. Reasons include:You don't have enough resources: You may have exhausted the supply of CPU or Memory in your cluster, in this case you need to delete Pods, adjust resource requests, or add new nodes to your cluster. See Compute Resources document for more information.You are using hostPort: When you bind a Pod to a hostPort there are a limited number of places that pod can be scheduled. In most cases, hostPort is unnecessary, try using a Service object to expose your Pod. If you do require hostPort then you can only schedule as many Pods as there are nodes in your Kubernetes cluster.My pod stays waitingIf a Pod is stuck in the Waiting state, then it has been scheduled to a worker node, but it can't run on that machine. Again, the information from kubectl describe ... should be informative. The most common cause of Waiting pods is a failure to pull the image. There are three things to check:Make sure that you have the name of the image correct.Have you pushed the image to the registry?Try to manually pull the image to see if the image can be pulled. For example, if you use Docker on your PC, run docker pull <image>.My pod stays terminatingIf a Pod is stuck in the Terminating state, it means that a deletion has been issued for the Pod, but the control plane is unable to delete the Pod object.This typically happens if the Pod has a finalizer and there is an admission webhook installed in the cluster that prevents the control plane from removing the finalizer.To identify this scenario, check if your cluster has any ValidatingWebhookConfiguration or MutatingWebhookConfiguration that target UPDATE operations for pods resources.If the webhook is provided by a third-party:Make sure you are using the latest version.Disable the webhook for UPDATE operations.Report an issue with the corresponding provider.If you are the author of the webhook:For a mutating webhook, make sure it never changes immutable fields on UPDATE operations. For example, changes to containers are usually not allowed.For a validating webhook, make sure that your validation policies only apply to new changes. In other words, you should allow Pods with existing violations to pass validation. This allows Pods that were created before the validating webhook was installed to continue running.My pod is crashing or otherwise unhealthyOnce your pod has been scheduled, the methods described in Debug Running Pods are available for debugging.My pod is running but not doing what I told it to doIf your pod is not behaving as you expected, it may be that there was an error in your pod description (e.g. mypod.yaml file on your local machine), and that the error was silently ignored when you created the pod. Often a section of the pod description is nested incorrectly, or a key name is typed incorrectly, and so the key is ignored. For example, if you misspelled command as commnd then the pod will be created but will not use the command line you intended it to use.The first thing to do is to delete your pod and try creating it again with the --validate option. For example, run kubectl apply --validate -f mypod.yaml. If you misspelled command as commnd then will give an error like this:I0805 10:43:25.129850 46757 schema.go:126] unknown field: commnd I0805 10:43:25.129973 46757 schema.go:129] this may be a false alarm, see https://github.com/kubernetes/kubernetes/issues/6842 pods/mypod The next thing to check is whether the pod on the apiserver matches the pod you meant to create (e.g. in a yaml file on your local machine). For example, run kubectl get pods/mypod -o yaml > mypod-on-apiserver.yaml and then manually compare the original pod description, mypod.yaml with the one you got back from apiserver, mypod-on-apiserver.yaml. There will typically be some lines on the "apiserver" version that are not on the original version. This is expected. However, if there are lines on the original that are not on the apiserver version, then this may indicate a problem with your pod spec.Debugging Replication ControllersReplication controllers are fairly straightforward. They can either create Pods or they can't. If they can't create pods, then please refer to the instructions above to debug your pods.You can also use kubectl describe rc ${CONTROLLER_NAME} to introspect events related to the replication controller.Debugging ServicesServices provide load balancing across a set of pods. There are several common problems that can make Services not work properly. The following instructions should help debug Service problems.First, verify that there are endpoints for the service. For every Service object, the apiserver makes one or more EndpointSlice resources available.You can view these resources with:kubectl get endpointslices -l kubernetes.io/service-name=${SERVICE_NAME} Make sure that the endpoints in the EndpointSlices match up with the number of pods that you expect to be members of your service. For example, if your Service is for an nginx container with 3 replicas, you would expect to see three different IP addresses in the Service's endpoint slices.My service is missing endpointsIf you are missing endpoints, try listing pods using the labels that Service uses. Imagine that you have a Service where the labels are:... spec: - selector: name: nginx type: frontend You can use:kubectl get pods --selector=name=nginx,type=frontend to list pods that match this selector. Verify that the list matches the Pods that you expect to provide your Service. Verify that the pod's containerPort matches up with the Service's targetPortNetwork traffic is not forwardedPlease see debugging service for more information.What's nextIf none of the above solves your problem, follow the instructions in Debugging Service document to make sure that your Service is running, has Endpoints, and your Pods are actually serving; you have DNS working, iptables rules installed, and kube-proxy does not seem to be misbehaving.You may also visit troubleshooting document for more information.