Troubleshooting Kubernetes CrashLoopBackOff error

CrasLoopBackOff is the most common problem, and it means that your pod is starting and crashing continuously.


Why is this happening?
The possible reasons are:

• the application inside your pod is not starting due to an error;
• the image your pod is based on is not present in the registry, or the node where your pod has been scheduled cannot pull from the registry;
• some parameters of the pod has not been configured correctly.

How to find the reason?
Retrieve the pod name:

kubectl get po -n mynamespace

NAME                    READY    STATUS            RESTARTS AGE
nginx-40395h6810-j90ed  1/1      Running            1       12d
mypod-390jo50wn3-sp40r  0/1      CrashLoopBackOff   2       1m

Then look at the logs of the pod:

kubectl logs mypod-390jo50wn3-sp40r -n mynamespace

If checking the logs is not enough and you can't find the reason of the error, you can look at kubernetes events:

kubectl get events -n mynamespace

You can see the events also describing the pod:

kubectl describe po mypod-390jo50wn3-sp40r -n mynamespace

Name:           mypod-390jo50wn3-sp40r
Namespace:      mynamespace
Node:           ip-10-10-8-68.eu-west-1.compute.internal/10.10.8.68

.....

Events:
  Type     Reason                 Age               From                                               Message
  ----     ------                 ----              ----                                               -------
  Normal   Scheduled              2m                default-scheduler                                  Successfully assigned nginx-5796d5bc7c-xsl6p to ip-10-10-8-68.eu-west-1.compute.internal
  Normal   SuccessfulMountVolume  2m                kubelet, ip-10-10-8-68.eu-west-1.compute.internal  MountVolume.SetUp succeeded for volume "config"
  Normal   SuccessfulMountVolume  2m                kubelet, ip-10-10-8-68.eu-west-1.compute.internal  MountVolume.SetUp succeeded for volume "default-token-cccxn"
  Normal   Pulled                 1m (x3 over 2m)   kubelet, ip-10-10-8-68.eu-west-1.compute.internal  Successfully pulled image "myapp"
  Normal   Created                1m (x3 over 2m)   kubelet, ip-10-10-8-68.eu-west-1.compute.internal  Created container
  Normal   Started                1m (x3 over 2m)   kubelet, ip-10-10-8-68.eu-west-1.compute.internal  Started container
  Warning  BackOff                1m (x5 over 1m)   kubelet, ip-10-10-8-68.eu-west-1.compute.internal  Back-off restarting failed container
  Warning  FailedSync             1m (x5 over 1m)   kubelet, ip-10-10-8-68.eu-west-1.compute.internal  Error syncing pod
  Normal   Pulling                57s (x4 over 2m)  kubelet, ip-10-10-8-68.eu-west-1.compute.internal  pulling image "myapp"
 
 

Look at the messages of the output, here you can find the reason of the error!