Pod is stuck in CrashLoopBackOff mode

If a pod has a CrashLoopBackOff status, then the pod probably failed or exited unexpectedly, and the log contains an exit code that isn't zero. Here are several possible reasons why your pod is stuck in CrashLoopBackOff mode:

1. Application failure: The application inside the container crashes shortly after starting, often due to misconfigurations, missing dependencies, or incorrect environment variables.
2. Incorrect resource limits: If the pod exceeds its CPU or memory resource limits, Kubernetes might kill the container. This issue can happen if resource requests or limits are set too low.
3. Missing or misconfigured ConfigMaps/Secrets: If the application relies on configuration files or environment variables stored in ConfigMaps or Secrets but they're missing or misconfigured, the application might crash.
4. Image pull issues: If there's an issue with the image (for example, it's corrupted or has an incorrect tag), the container might not start properly and fail repeatedly.
5. Init containers failing: If the pod has init containers and one or more fail to run properly, the pod will restart.
6. Liveness/Readiness probe failures: If liveness or readiness probes are misconfigured, Kubernetes might detect the container as unhealthy and restart it.
7. Application dependencies not ready: The application might depend on services that aren't yet ready, such as databases, message queues, or other APIs.
8. Networking issues: Network misconfigurations can prevent the application from communicating with necessary services, causing it to fail.
9. Invalid commands or arguments: The container might be started with an invalid ENTRYPOINT, command, or argument, leading to a crash.

For more information about the container status, see Pod Lifecycle - Container states.

Consider the following options and their associated kubectl commands.

Option	kubectl command
Debug the pod itself	kubectl describe pod <pod-name>
Debug the replication controllers	kubectl describe replicationcontroller <controller-name>
Read the termination message	kubectl get pod <pod-name> --output=yaml
Examine the logs	kubectl logs <pod-name>

Note

A pod can also have a CrashLoopBackOff status if it has finished deployment, but it's configured to keep restarting even if the exit code is zero. For example, if you deploy a busybox image without specifying any arguments, the image starts, runs, finishes, and then restarts in a loop:

$ kubectl run nginx --image nginx
pod/nginx created

$ kubectl run busybox --image busybox
pod/busybox created

$ kubectl get pods --watch
NAME     READY  STATUS             RESTARTS  AGE
busybox  0/1    ContainerCreating  0         3s
nginx    1/1    Running            0         11s
busybox  0/1    Completed          0         3s
busybox  0/1    Completed          1         4s
busybox  0/1    CrashLoopBackOff   1         5s

$ kubectl describe pod busybox
Name:         busybox
Namespace:    default
Priority:     0
Node:         aks-nodepool<number>-<resource-group-hash-number>-vmss<number>/<ip-address-1>
Start Time:   Wed, 16 Aug 2023 09:56:19 +0000
Labels:       run=busybox
Annotations:  <none>
Status:       Running
IP:           <ip-address-2>
IPs:
  IP:  <ip-address-2>
Containers:
  busybox:
    Container ID:   containerd://<64-digit-hexadecimal-value-1>
    Image:          busybox
    Image ID:       docker.io/library/busybox@sha256:<64-digit-hexadecimal-value-2>
    Port:           <none>
    Host Port:      <none>
    State:          Waiting
      Reason:       CrashLoopBackOff
    Last State:     Terminated
      Reason:       Completed
      Exit Code:    0
      Started:      Wed, 16 Aug 2023 09:56:37 +0000
      Finished:     Wed, 16 Aug 2023 09:56:37 +0000
    Ready:          False
    Restart Count:  2

If you don't recognize the issue after you create more pods on the node, then run a pod on a single node to determine how many resources the pod actually uses.

Third-party information disclaimer

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

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