CrashLoopBackOff

Learn to identify the CrashLoopBackOff error.

CrashLoopBackOff

CrashLoopBackOff shows that the container starts and crashes immediately, and that the kubelet restarts it with an increasing wait each time (10 s, 20 s, 40 s ... at most 5 min). It's a symptom, not a cause; the cause is in the container's last log:

$ kubectl get pod api-xyz
NAME      READY   STATUS             RESTARTS      AGE
api-xyz   0/1     CrashLoopBackOff   6 (90s ago)   8m
$ kubectl logs api-xyz --previous
Error: DATABASE_URL tanımlı değil
$ kubectl describe pod api-xyz | grep -A2 "Last State"
    Last State:  Terminated
      Reason:    Error
      Exit Code: 1

Exit codes

The exit code narrows down the cause:

1: an application error (look at the log)
126 / 127: the command couldn't run / wasn't found (a wrong command)
137: SIGKILL; usually OOMKilled or a liveness failure
143: shut down cleanly with SIGTERM

kubectl get pod api-xyz -o jsonpath='{.status.containerStatuses[0].lastState.terminated.exitCode}'
137

Exercise The cause of the crash

Write three commands: show the previous container log of api-xyz; print the last exit code with jsonpath='{.status.containerStatuses[0].lastState.terminated.exitCode}'; set the memory limit of the api container of the api deployment to 512Mi with kubectl set resources.

Show example solution

kubectl logs api-xyz --previous
kubectl get pod api-xyz -o jsonpath='{.status.containerStatuses[0].lastState.terminated.exitCode}'
kubectl set resources deployment/api -c api --limits=memory=512Mi

Test yourself

If you see Reason: OOMKilled and Exit Code: 137 in Last State, what is the cause?
- A wrong command
- A network error
- The container exceeded its memory limit
- The image wasn't found
Show answer

The container exceeded its memory limit — 137 = 128 + 9 (SIGKILL); the fix is raising limits.memory or finding the leak.

Look at the crashed container's output.

kubectl logs api-xyz ____

Show answer

kubectl logs api-xyz --previous

Match the exit codes.

1

Application error
127

Command not found
137

SIGKILL / OOMKilled
143

Closed with SIGTERM

Next lesson: Pending Pod

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies