CrashLoopBackOff Error in Kubernetes - Sanity Checklist
Tags: kubernetes, cloud, devops, aws
Published: 2022-09-12 01:45:27

This is a very common problem when working with Kubernetes and I am writing this article fresh out of 31 hours of debugging. The fix in my case was very simple which I will make sure to talk about at the end. But for those who didn't come here to read my stories let's dive into what this error is and how to resolve it.

The CrashLoopBackOff error basically means that your pod keeps restarting for some reason. There is no stable state. This could be due to the following reasons:

1. **Permission Issues**

If you are working in a cloud environment like AWS, you need to make sure that the appropriate roles are assigned to your cluster and your worker nodes so that they can interact properly. If you are working locally in something like Minikube still make sure that the appropriate permissions are set.

2. **Clashing Ports**

You may be trying to access ports that are in use by other processes. Try changing the ports. If two or more containers are trying to access the same port in the same pod. That can cause this issue as well.

3. **Network Issues**

One possible reason I saw while reading docs on AWS was that sometimes your subnets may have run out of free IP addresses. So do ensure that this is not the case. Some other times, it may be that the subnets do not automatically allocate IP addresses or maybe they just do not allow egress to resources your pod might be trying to access. 

4. **External Resources**

Check that the external resources or dependencies that your pod or container needs to access are in a healthy state. It could be a file, a database, or even libraries from "npm install". If you are using something like AWS RDS, ensure that the security group configurations are properly set.

5. **Configuration Files**

This goes without saying. Please do check your config files. Sometimes it could just be a typo somewhere. Also try to carefully check the commands that you have used so far in deployment. Maybe you misspelled a name or something.

6. **System Specifications**

Now sometimes, you may not have enough resources like memory or whatnot on the nodes you may have allocated to run your pods so check that the specs of your machines are right. 

The best tool for finding errors

`kubectl logs [pod name]`

If you have read up to this point and you are not interested in reading about my experience, you can stop here.

Amazing, so you do want to hear about it. Okay so this is what happened. I had a cluster set up on AWS EKS and some node groups created. I had done everything to ensure that my steps were golden but still I had the CrashLoopBackOff error. So I noticed that whenever I tried to get the logs for my pod I got a format error that looked like this 

`exec /usr/local/bin/docker-entrypoint.sh: exec format error`

A little more research here, a little stack overflow there and I found that it was because I built my docker image with a Mac M1 pro and my worker nodes ran a Linux OS. I never thought that would cause a conflict. So I fixed the build using

`docker build -t [image-name] . --platform=linux/amd64`

When I pushed it to docker hub and checked the pods again, the error was gone. So there ye have it, another possible reason to get the CrashLoopBackOff Error. Check that your docker image build is compatible with your worker node OS. To achieve reproducibility I suggest writing a script. Thanks for reading.