Encountering any error in a Kubernetes environment is never a joyful experience. But, as errors go, if you're running into CrashLoopBackOff, you're probably going to have an easy time of remedying the situation and continuing on with your projects. 

If a pod is returning an error within Kubernetes and continuously restarting itself, you're likely experiencing what is known as CrashLoopBackOff. This is a fairly common error, in which a pod, for one of many reasons, gets stuck in a continual loop of crashing and restarting.

What Causes CrashLoopBackOff in Kubernetes?

While CrashLoopBackOff is a common error and one that's typically easy to fix, there are many potential underlying causes that could lead to this error appearing. Because of this, there are many more than just a singular solution.

Typically, the most common reasons that CrashLoopBackOff occurs is due to:

• Misconfigurations - Typically, one of the main reasons that a Kubernetes ecosystem experiences a CrashLoopBackOff is due to the fact that there is a misconfiguration in the file.

• Locked database or file - If the database that a pod is trying to access has already been locked by other pods, you'll get an infinite loop of trying to access, not being able to, shutting down, restarting, and trying again. Equally, if a singular file has been locked by a container, then you'll get a crash loop.

• Insufficient resources - Memory resources are a huge reason that people run into a CrashLoopBackOff error. If your pod attempts to run a process but doesn't have enough resources, then it will be unable to do so, causing this error. As the pod will continuously attempt to run that process, until it receives the additional resources that it needs, it will just experience the titular error of this article.

• Connection issues - If a kube-BNS fails to connect to any of the third-party services that they should be connected to, then you're likely going to return with a CrashLoopBackOff error.

While these are the major reasons for the errors, there are even more CrashLoopBackOff error causes that could be underpinning your issue. 

How to Troubleshoot CrashLoopBackOff

As apparent from the vast range of different possible sources that could potentially cause CrashLoopBackOff, fixing this error isn't as easy as simply following a direct process. Instead, the first thing you need to do to even understand what went wrong with your system is to troubleshoot this error.

If you've recently scaled your application, there is a high chance that you'll run into this error. With this in mind, you can move through three distinct steps in order to troubleshoot the message:

• Discover - In the first stage of troubleshooting, you should aim to make a note of any pods that are currently in the restart loop. There could be a singular pod in your system that's returning CrashLoopBackOff, or a whole system of them. Knowing which pods are returning the error is always the first step toward fixing them.

• Gather - Once you find the pods that aren't working, you can then use a range of Kubernetes commands to get more information. The most useful of these will be kubectl get pods, which will then give you a list of all the currently running pods and their state in that moment. This will help you find the true range of the different pods that are currently faulty in your system, as well as some more information about the true source of their failure.

• Target - From your larger list of the current pods in your system, you can then begin to directly target specific pods. By finding those that are currently in a CrashLoopBackOff error, you can then run 'kubectl describe pod [variable]' in order to get the name of the pod you want to know about, as well as the command variable. This will give you all the information you need to then be able to find a fix to your problem.

After this troubleshooting process, you'll have a much better idea about what possible causes are the main player in your error. From there, you only need to begin to reverse the errors on each pod until you're left with a completely healthy pod ecosystem. 

What Is the Benefit of CrashLoopBackOff?

Although all errors are generally frustrating, there is actually one central benefit of receiving the CrashLoopBackOff error, which is why developers don't grimace quite as much when they get this response. When you set a pod's restart policy to 'always', it will continually try to restart, creating the loop of crashing and restarting that is known as CrashLoopBackOff.

While this is an error that needs to be fixed, because the pod is actively restarting and trying to work, you can always interact with it to troubleshoot information. This gives you a larger base of your inquiry into why an error is occurring, helping you to then put in place actions toward fixing the root of the problem.

If a pod was simply crashing with no further response, it would be slightly harder to get the necessary degree of information that you'll need when trying to fix the underlying issue.

Final Thoughts

Of all the possible errors you could encounter when managing and developing within the Kubernetes ecosystem, CrashLoopBackOff is far from the worst. As a common Kubernetes error, this is an easy fix if you go through the process of troubleshooting. 

When working through different possible iterations of this error, there are several causes. However, no matter the cause, you'll be able to troubleshoot this error and then formulate a response that will have you back working at maximum capacity in no time.