CoreDNS CrashLoopBackOff Kubernetes issue

pain with crashing coredns

matto@pc:~$ kubectl get pods --namespace=kube-system
NAME                          READY   STATUS    RESTARTS   AGE
coredns-66bff467f8-j9lcr      1/1     Running   60         8m17s
coredns-66bff467f8-lf6vj      1/1     CrashLoopBackoff   99          8m17s

root cause of the issue

is described at https://github.com/coredns/coredns/tree/master/plugin/loop#troubleshooting

checking your /etc/resolv.conf

This file is overwritten by your network config

what helped me, to keep it's content:

chattr +i /etc/resolv.conf

this makes it immutable

sudo systemctl stop kubelet
sudo systemctl stop docker
sudo iptables --flush
sudo iptables -tnat --flush
sudo iptables -P FORWARD ACCEPT
sudo systemctl start docker
sudo systemctl start kubelet
sudo kubectl delete pods -n kube-system -l k8s-app=kube-dns 

then, make sure that coreDNS starts and there are no restarts

sudo kubectl get pods --namespace=kube-system 

NAME                          READY   STATUS    RESTARTS   AGE
coredns-66bff467f8-bx5zc      1/1     Running   0          62s
coredns-66bff467f8-xv5sd      1/1     Running   0          62s

There should be no restarts !

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