Debug Kubernetes CrashLoopBackOff in 30 Seconds

Struggling with a pod stuck in CrashLoopBackOff? This quick guide, originally published on devopsstart.com, shows you the exact commands to diagnose the root cause in seconds.

The Problem

Your pod is stuck in CrashLoopBackOff and you need to find out why — fast.

The Solution

kubectl logs <pod-name> --previous

The --previous flag shows logs from the last crashed container instance. This is the single most useful flag for debugging crash loops.

Combine with describe for the full picture

kubectl describe pod <pod-name> | grep -A 5 "Last State"

This shows the exit code and reason for the last termination:

Last State:  Terminated
  Reason:    OOMKilled
  Exit Code: 137

Common Exit Codes

Code	Meaning	Fix
1	Application error	Check app logs
137	OOMKilled	Increase memory limits
139	Segfault	Check binary compatibility
143	SIGTERM	Graceful shutdown issue

Why It Works

Kubernetes keeps logs from the previous container instance even after it crashes. Without --previous, you'd only see logs from the current (possibly empty) instance that hasn't had time to produce output before crashing again.