Kubernetes Pod Status CrashLoopBackOff

The CrashLoopBackOff status indicates that a Kubernetes pod's container repeatedly starts, crashes, and then restarts after a back-off delay. This usually means the application inside the container is failing to start or encountering a fatal error shortly after startup, preventing the pod from reaching a 'Running' state.

Common Causes

Application errors or misconfigurations within the container (e.g., incorrect startup commands, missing dependencies, unhandled exceptions, incorrect environment variables).
Insufficient resource requests/limits (CPU, memory) causing the container to be OOMKilled (Out Of Memory Killed) or throttled.
Incorrect container image or tag, leading to a non-existent executable or corrupted application.
Persistent volume issues (e.g., volume not mounting, permissions errors, full disk, incorrect access modes).
Liveness or readiness probe failures, causing Kubernetes to restart the container even if the application might be starting slowly.
Configuration issues (ConfigMaps, Secrets) not being correctly mounted or accessed by the application.

How to Fix

1 Examine Pod Logs

The most crucial first step is to check the logs of the crashing container. This often reveals the exact error message or reason for the application's failure.

BASH

$ kubectl logs <pod-name> -n <namespace>

2 Describe the Pod for Events and Status

Use `kubectl describe pod` to get detailed information about the pod's state, events, and container status. Look for 'Events' at the bottom for clues like OOMKilled, failed mounts, or probe failures. This can also show why the container exited.

BASH

$ kubectl describe pod <pod-name> -n <namespace>

3 Verify Container Image, Command, and Arguments

Ensure the container image is correct and accessible, and that the `command` and `args` defined in the pod specification are valid and point to an executable within the container. A common mistake is an incorrect entrypoint or missing executable.

BASH

$ kubectl get pod <pod-name> -o yaml -n <namespace> | grep -E 'image:|command:|args:'

4 Review Liveness and Readiness Probes

If probes are configured too aggressively (e.g., too short `initialDelaySeconds`, too low `failureThreshold`), they can cause a healthy application to be restarted before it's fully ready. Temporarily disable or relax probes to see if the pod stabilizes, then reconfigure them appropriately.

BASH

 $ # Example of relaxing a liveness probe in pod YAML:
# livenessProbe:
#   httpGet:
#     path: /healthz
#     port: 8080
#   initialDelaySeconds: 30  # Increase initial delay
#   periodSeconds: 10
#   timeoutSeconds: 5
#   failureThreshold: 6    # Increase failure threshold

5 Increase Resource Requests/Limits

If the pod is being OOMKilled (Out Of Memory Killed) or throttled due to insufficient CPU, increase the `resources.limits.memory` and `resources.limits.cpu` in the pod's container specification. Check `kubectl describe pod` events for 'OOMKilled'.

BASH

 $ # Example of increasing resources in pod YAML:
# resources:
#   limits:
#     cpu: "1"
#     memory: "1Gi"
#   requests:
#     cpu: "500m"
#     memory: "512Mi"