How to Troubleshoot Common Kubernetes Issues
Are you tired of struggling with Kubernetes issues? Do you want to become a Kubernetes troubleshooting master? If you answered yes to these questions, then you're in the right place! Kubernetes can be a complex system, and sometimes things don't go as planned. But don't worry, we're here to help you troubleshoot common Kubernetes issues.
In this article, we're going to cover the top 10 issues that you might face while working with Kubernetes, and provide you with solutions that will help you troubleshoot them. So, let's get started!
Kubernetes issue #1: Nodes are not ready
One of the most common Kubernetes issues is when nodes are not ready. This issue can occur due to a variety of reasons, such as incorrect configuration, network problems, or resource allocation issues. So, what can you do to troubleshoot this issue?
The first step is to ensure that the nodes have been initialized correctly. You can check the status of the nodes by running the following command:
kubectl get nodes
If you see that some nodes are not ready, you should check the reason for that by running:
kubectl describe node <node-name>
This command will provide you with detailed information about the node, including its status, conditions, and events. Look for any events that are marked as "Failed" or "Error", and try to resolve those issues.
If the node is not ready due to resource allocation issues, you can check the resource requests and limits for the pods running on the node by running:
kubectl describe pod <pod-name>
This command will show you the resource requests and limits for the pods, which you can adjust as needed to free up resources for the node.
Kubernetes issue #2: Pods are not starting
Another common Kubernetes issue is when pods are not starting. This issue can occur due to a variety of reasons, such as incorrect configuration, network problems, or lack of resources. So, what can you do to troubleshoot this issue?
The first step is to check the status of the pod by running the following command:
kubectl get pods
If you see that the pod is in a "Pending" state, it might be due to a lack of resources on the node or the cluster. You can check the resource usage of the cluster by running:
kubectl top nodes
This command will show you the CPU and memory usage of each node. If you see that the usage is high, you might want to consider adding more nodes to the cluster or increasing the resources available on the current nodes.
If the pod is stuck in a "ContainerCreating" state, it could be due to issues with the container image or configuration. You can check the logs of the container by running:
kubectl logs <pod-name> <container-name>
This command will show you the logs of the container, which can help you identify any issues with the image or configuration.
Kubernetes issue #3: Services are not accessible
Another common Kubernetes issue is when services are not accessible. This issue can occur due to a variety of reasons, such as incorrect configuration, network problems, or service discovery issues. So, what can you do to troubleshoot this issue?
The first step is to verify that the service is running by running the following command:
kubectl get services
If you see that the service is not running, you can check the logs of the pod by running:
kubectl logs <pod-name>
This command will show you the logs of the pod, which can help you identify any issues with the service.
If the service is running but not accessible, it could be due to service discovery issues. You can check the DNS resolution for the service by running:
This command will show you the IP address associated with the service name, which you can use to access the service. If the DNS resolution is incorrect, you might want to check the configuration of the DNS services used by your cluster.
Kubernetes issue #4: ConfigMaps are not working
ConfigMaps are used to store configuration data that can be accessed by Kubernetes resources at runtime. One common issue with ConfigMaps is when they are not working as intended. This issue can occur due to a variety of reasons, such as incorrect configuration, storage problems, or Pod design errors. So, what can you do to troubleshoot this issue?
The first step in troubleshooting ConfigMap issues is verifying the resource is defined properly. You can check the defined ConfigMaps by running the following command:
kubectl get configmaps
If you see that the ConfigMaps aren't present, you might have to check if they were correctly created or if there are any issues with the cluster that caused them to not be created.
After verifying the ConfigMaps are defined correctly, ensure they are mounted correctly inside a Pod as volume or environment variables. You can check the pod configuration running:
kubectl describe pod <pod-name>
Search for the section that describes the Pod's containers which should have the ConfigMap mounted.
If the ConfigMaps are mounted to a volume, you can validate they are correctly added inside the container conducting the following:
kubectl exec -it <pod-name> /bin/bash # access the Pod's shell cd <path_to_the_volume>/<ConfigMap_directory> ls # validate the ConfigMap files are present inside this directory
When ConfigMaps are stored as Environment Variables, you can look them up by executing the following:
kubectl exec -it <pod-name> /bin/bash # access the Pod's shell env | grep <ConfigMap_name> # see if this environment variable was defined inside the container
Kubernetes issue #5: PersistentVolumes are not being mounted
PersistentVolumes are a vital component of stateful applications running inside Kubernetes. They provide a persistent storage resource for applications that require data that survives Pod termination or rescheduling. One common issue with PersistentVolumes is when they are not mounted as expected by the Pod. This issue can be due to a variety of reasons, such as incorrect references to the storage resource, permission problems or issues with the cluster's StorageClass definition. So, what can you do to troubleshoot this issue?
The first step in troubleshooting PersistentVolumes mounting issues is checking the PV definition to make sure it correctly describes your storage backend. You can list them by running:
kubectl get pv
Search for the PV that you expect to source your Pod's volume and validate it's claimable for use.
Continuing, validate the Pod definition includes the expected volume definition, double-checking the volume name and mountPath. You can verify that via:
kubectl describe pod <pod-name>
If it's all good on the Pod definition's side, validate the Pod's status against the PVC containing this volume reference, and check if it's in a bound state:
kubectl get pvc <pvc-name>
If it's not in a bound state, something could have gone wrong with the claim process. You should think of troubleshooting it from the PVC handling side.
If the PVC is in a bound state, double-check if there are any permission-related issues with the Pod trying to access it. Some storage solutions, like CephFS, require a Pod mount explicitly with a
user parameter, to allow access.
Kubernetes issue #6: Issues with network communication
A frequent issue with Kubernetes is related to pods' networking configuration. Whether it's accessing external resources or connectivity issues with other nodes inside the cluster, it's a very critical issue to troubleshoot quickly. Some of the root causes include service discovery misconfigurations, IPTables rules, or missing network plugins in the cluster's configuration.
If the Pods aren't able to reach external resources, determine whether it's due to DNS issues or whether the traffic is in fact being forbidden due to IPTables rules. You can perform a
curl command to a publicly accessible endpoint to check if the Pods themselves are responsible for issues.
kubectl exec <pod-name> -- curl http://checkip.amazonaws.com
Check the Cluster-wide network policy applied. It's possible that the Pod IP ranges are not correctly defined, blocking network communications. Validate the network policy by running:
kubectl get networkpolicy
Extend the reach of network checks to the Cluster-level. For example, check if the KubeDNS POD is running and accessible inside the Cluster. Test it by running:
kubectl exec busybox -- nslookup kube-dns.kube-system.svc.cluster.local
If you can't access an internal resource, such as another Pod, check for Network Policy violations. Check the NetworkPolicy configuration by running:
kubectl get networkpolicy
Consider if there's an implemented policy restricting Pod-to-Pod communication.
Kubernetes issue #7: Issues deploying applications
If you're attempting to deploy applications in Kubernetes, you might experience issues with pods not being created, terminating or going into crash loops. Issues with deploying applications can be because of numerous reasons, such as issues with Docker images, Pod networking or storage accessibility.
Ensure Pods are being scheduled correctly by determining if the Pod manifest or deployment definitions have been created correctly. You can do that by running:
kubectl get pod
Check out the detailed information regarding the pod's condition, including the state and the reason why there was an error occurred.
Check out the Pod logs to determine whether it was due to issues with the Docker image, and do this by running:
kubectl logs <Pod-Name>
Finally, validate the storage requirements for the Pod. Most of the issues around Pod deployment will ultimately be related to storage issues. You can verify the Pod is correctly referencing the PVC and StorageClass and works through the following command:
kubectl get pvc <pvc-name>
In case there's an error message, you need to troubleshoot it from the Persistent Volume handling side.
Kubernetes issue #8: Issues with resource utilization
Resource allocation and utilization are one of the most essential parts of Kubernetes. Over and under allocating or incorrectly sharing resources can lead to failure for the applications running in the cluster. Some common resource allocation issues include insufficient CPU or memory quotas, Pod scheduling problems or malfunctioning nodes.
In Kubernetes, the best practice for resource allocation and quota is to use the Kubernetes ResourceQuota object. You can see the current quota allocations by running:
kubectl describe quota
Check out the Nodes, Pod and Pods Resource information. It will give you an insight into whether you've allocated enough CPU and memory resources for pods.
Another way to examine your Nodes condition is by running the
top command. This command shows the CPU and memory usage for every Node in the cluster.
kubectl top nodes
If the Pod scheduling is a problem, verify that the corresponding node has been set up correctly by checking the node's status, as explained in Issue #1 of this article.
Kubernetes issue #9: Issues with Storage Classes
Storage Classes are a fundamental component of Kubernetes. The correct configuration of Storage Classes is necessary for successful data storage in Pods. Misconfigurations can cause issues with data volume replication, data read and write bottlenecks or Pod scheduling.
When troubleshooting Storage Class issues, check that the proper storage backend has been selected and configured for Kubernetes. You can list the Storage Classes in the cluster by running:
kubectl get sc
If you don't see the appropriate Storage Class, you will need to create it explicitly with the required configuration.
Double-check that the appropriate storage classes are applied to your PVCs assigned to your Pod. If the storage class isn't applied correctly, you can update the
PersistentVolumeClaim manifest with the right
Kubernetes issue #10: Issues with namespace creation
Kubernetes Namespace is a conceptual way to partition a cluster, enabling to have multiple teams sharing the same K8s Cluster infrastructure while avoiding overlap between their resources. Misconfigurations of Namespaces can cause issues with Pod scheduling or limited access to cluster-wide resources.
The first step to troubleshoot Namespace creation issues is ensuring that the Namespace is already present. You can list the currently present namespaces by running:
kubectl get namespaces
In case it isn't, follow the procedure in the Kubernetes docs to create it.
Ensure trust between namespaces by verifying that the appropriate RBAC rules are defined, and check if cross-namespace communication is allowed through the Service configurations.
Congratulations, you've made it to the end of this article! Now, you know how to troubleshoot common Kubernetes issues like a pro. Being able to diagnose and identify issues is essential to ensure that your Kubernetes cluster runs smoothly and your applications are always available.
Remember, Kubernetes is a complex system, and issues can occur due to a variety of reasons. But by following the solutions outlined in this article, you can troubleshoot the most common issues and keep your Cluster running healthy.
If you enjoyed this article and would like to learn more about Kubernetes, please visit our website, k8s.management, for more tips, tricks and tutorials about Kubernetes management.
Editor Recommended SitesAI and Tech News
Best Online AI Courses
Classic Writing Analysis
Tears of the Kingdom Roleplay
Database Ops - Liquibase best practice for cloud & Flyway best practice for cloud: Best practice using Liquibase and Flyway for database operations. Query cloud resources with chatGPT
Fanfic: A fanfic writing page for the latest anime and stories
Deploy Code: Learn how to deploy code on the cloud using various services. The tradeoffs. AWS / GCP
Hands On Lab: Hands on Cloud and Software engineering labs
Data Quality: Cloud data quality testing, measuring how useful data is for ML training, or making sure every record is counted in data migration