Question

Users report that all applications in the cluster suddenly cannot resolve any DNS names, both internal (svc.cluster.local) and external. Pods themselves start fine and node-to-node connectivity works. Running 'kubectl get pods -n kube-system' shows no CoreDNS pods listed at all, and 'kubectl get deploy coredns -n kube-system' shows READY 0/0. Recent cluster maintenance was performed by another engineer. What is the most likely cause and the correct fix?

Accepted Answer

The CoreDNS Deployment was scaled to 0 replicas; scale it back up with 'kubectl scale deployment coredns -n kube-system --replicas=2'

Answer

The CoreDNS ConfigMap Corefile is corrupted; edit the ConfigMap to restore the default forward directive

Answer

kube-proxy is not programming iptables rules for the kube-dns Service; restart the kube-proxy DaemonSet

Answer

The nodes are under memory pressure and evicted CoreDNS pods; drain and reboot the affected nodes