Kubernetes Troubleshooting Basics and Solving Common Errors

How Does Kubernetes Troubleshooting Work?

Kubernetes is a popular open-source system for automating the deployment, scaling, and management of containerized applications. It provides a platform for deploying, running, and managing containerized applications, such as Docker or Rocket containers, in a clustered environment.

Kubernetes troubleshooting involves identifying and resolving issues that may arise when using Kubernetes to deploy, run, and manage containerized applications. Some common issues that may need to be troubleshooted include problems with the deployment or scaling of applications, issues with the Kubernetes API, networking problems, or issues with application performance and uptime.

Common Commands Used for Kubernetes Troubleshooting

Kubernetes provides a number of tools and features to help you troubleshoot issues that may arise in your applications, including:

• kubectl: a powerful tool for managing and troubleshooting Kubernetes clusters. It provides a wide range of commands for inspecting and manipulating the various resources in a cluster, such as pods, nodes, and deployments.
• kubectl describe: provides detailed information about a particular resource in a cluster, including its status, events, and logs. This can be useful for understanding what is happening with a particular resource and identifying potential issues.
• kubectl logs: allows you to view the logs for a particular pod or container in a cluster. This can be useful for understanding why an application is failing or behaving unexpectedly.
• kubectl exec: allows you to run a command inside a container in a pod. This can be useful for debugging issues or inspecting the state of an application from inside the container.
• kubectl explain: provides detailed documentation about a particular resource or field in Kubernetes. This can be useful for understanding how a particular resource or field is used and what it does.

A Process for Kubernetes Troubleshooting

In addition to these tools, there are also a number of best practices and approaches you can use when troubleshooting issues in a Kubernetes cluster. These include:

• Isolating the issue: It is important to narrow down the scope of the issue as much as possible, so that you can focus on the specific component or resource that is causing the problem.
• Gathering information: Collect as much information as possible about the issue, including logs, events, and any other relevant details.
• Debugging: Use the tools and features provided by Kubernetes, as well as any other debugging techniques you are familiar with, to understand the root cause of the issue and identify a solution.
• Applying fixes: Once you have identified a fix for the issue, apply it carefully and test to ensure that it resolves the problem.

Solving Common Kubernetes Errors

CrashLoopBackOff

CrashLoopBackOff is a common error state in Kubernetes that indicates that a container or application is crashing repeatedly and the system is unable to restart it. This can happen for a variety of reasons, such as when the application code is faulty or when the application is unable to access its dependencies. Learn more about the CrashLoopBackOff error in this detailed post.

Solution:

To identify a CrashLoopBackOff error, you can use the kubectl get pods command to view the status of all pods in the Kubernetes cluster. This will show you which pods are running, which pods are not running, and why they are not running. If a pod is in the CrashLoopBackOff state, it will be marked as such in the output of the kubectl get pods command.

To address a CrashLoopBackOff error, you will need to determine the cause of the error and take appropriate action to fix it. Once you have identified the cause of the error, you can take appropriate action to fix it. This could involve updating the application code or dependencies, modifying the application configuration, or changing the container environment. It may also be necessary to redeploy the application or recreate the container in order to apply the changes and ensure that the application runs correctly.

Exit Code 1

In Kubernetes, this error code typically indicates that the container or application has encountered an error and has stopped running. This could be due to a variety of reasons, such as an unhandled exception in the application code, a problem with the application’s dependencies, or an issue with the container environment.

Solution:

To address an exit code 1 error in Kubernetes, you will need to determine the cause of the error and take appropriate action to fix it. Here are some steps you can follow to troubleshoot and resolve this issue:

1. Check the application logs—the application logs can provide valuable information about what went wrong and why the application stopped running. You can view the logs using the kubectl logs command or by accessing the logs through a logging service such as Elasticsearch or Splunk.
2. Review the application configuration—the configuration of the application, including its dependencies and resource requirements, can affect its behavior and may be the cause of the error. You can review the configuration by examining the deployment manifest or by using the kubectl describe command to view the configuration of the deployment or pod.
3. Check the container environment—the container environment, including the operating system, runtime, and libraries, can also affect the behavior of the application. You can check the environment by using the kubectl exec command to run a shell in the container and examine its environment.
4. Use debugging tools—if the cause of the error is not clear from the application logs or configuration, you may need to use specialized debugging tools to diagnose the problem. This can involve using a debugger to attach to the running application, using a profiler to identify performance bottlenecks, or using other tools to examine the state of the application or container.

Once you have identified the cause of the error, you can take appropriate action to fix it. This could involve updating the application code or dependencies, modifying the application configuration, or changing the container environment. It may also be necessary to redeploy the application or recreate the container in order to apply the changes and ensure that the application runs correctly.

Kubernetes Node Not Ready

In Kubernetes, a node is considered “not ready” when it is unable to accept or run new workloads. This can happen for a variety of reasons, such as when the node is experiencing technical issues, when the node is undergoing maintenance, or when the node has reached its resource limits.

When a node is not ready, it will typically be marked as such in the Kubernetes control plane, and new workloads will not be scheduled to run on the node. This can cause issues with the availability and performance of applications, as well as with the overall health and stability of the Kubernetes cluster.

Solution:

To remove a failed node from a Kubernetes cluster, you can use the kubectl drain command. This command will first evict any pods that are running on the node, and then mark the node as unschedulable so that no new pods are scheduled to run on it.

Once all of the pods have been evicted and the node is no longer being used, you can then use the kubectl delete node command to delete the node from the cluster.

To delete stateful pods with unknown status, you can first use the kubectl get pods command to list all of the pods in your cluster, and then use the kubectl delete pod command to delete the ones that have an unknown status. For example, you could use a command like the following:

kubectl get pods –output=json | \

jq ‘.items[] | select(.status.phase == null) | .metadata.name’ | \

xargs kubectl delete pod

This command works as follows:

1. Runs the kubectl get pods command to list all of the pods in your cluster in JSON format.
2. Runs the jq command-line JSON processor to filter the list of pods, selecting only the ones that have a null status.phase field (indicating that their status is unknown).
3. Uses the xargs command to build a list of kubectl delete pod commands, one for each of the selected pods, and run those commands to delete the pods.

Note that this approach will only work for pods that are not part of a Kubernetes deployment, as the kubectl delete pod command will not delete pods that are managed by a deployment. For those pods, you will need to delete the deployment itself using the kubectl delete deployment command.

Conclusion

In conclusion, CrashLoopBackOff and other Kubernetes errors can be frustrating and difficult to troubleshoot, but understanding what they mean and how to address them is an important part of working with Kubernetes.

By familiarizing yourself with common errors like Exit Code 1, Exit Code 125, and CrashLoopBackOff, and learning how to use tools like kubectl and jq to troubleshoot and resolve these errors, you can become a more effective Kubernetes user and avoid many of the pitfalls that can arise when working with this powerful system.