How to fix Pod Unknown in Kubernetes

First, verify the node health:

kubectl get nodes

Look for nodes in NotReady status. Get details:

kubectl describe node <node-name>

Check the Conditions section for:
- Ready: False or Unknown
- MemoryPressure, DiskPressure, PIDPressure
- NetworkUnavailable

If the node is NotReady, that's the root cause of Unknown pods.

List all pods in Unknown state:

kubectl get pods --all-namespaces -o wide | grep Unknown

If all Unknown pods are on the same node, the issue is node-level, not pod-level:

# Find which node has the problems
kubectl get pods -o wide | grep Unknown | awk '{print $7}' | sort | uniq -c

If you have node access, check kubelet:

# SSH to node
ssh <node-ip>

# Check kubelet status
systemctl status kubelet

# View kubelet logs
journalctl -u kubelet -f

# Check node resources
free -h
df -h

Common issues:
- Kubelet crashed due to OOM
- Disk full preventing kubelet from operating
- Certificate expired for kubelet-API communication

Kubernetes will automatically recover when communication resumes:

1. If node comes back online, pod status updates automatically
2. If node stays offline past pod-eviction-timeout (default 5 minutes), pods are rescheduled

Monitor recovery:

kubectl get pods -w  # Watch for status changes
kubectl get nodes -w

For managed Kubernetes (EKS, GKE, AKS), the cloud provider may automatically replace unhealthy nodes.

If the node won't recover and pods remain Unknown:

kubectl delete pod <pod-name> --grace-period=0 --force

Caution: Force deletion tells Kubernetes to forget about the pod, but:
- The container may still be running on the failed node
- Attached volumes may not be properly released
- PersistentVolumes might show as still attached

Only use force delete when you're certain the node won't recover or has been terminated.

If the node is permanently lost:

# Drain remaining pods (will fail but marks intent)
kubectl drain <node-name> --ignore-daemonsets --delete-emptydir-data --force

# Delete the node
kubectl delete node <node-name>

After node deletion:
- Pods are marked for rescheduling
- PersistentVolumes should detach (may need cloud provider cleanup)
- New nodes can join to replace capacity

For cloud providers, terminated instances are usually cleaned up automatically.