ERVFAIL kubernetes dns_error ai_generated true

CoreDNS: SERVFAIL for cluster.local, dial tcp: lookup on: no such host

ID: kubernetes/k8s-dns-resolution-failed

Also available as: JSON · Markdown
85%Fix Rate
87%Confidence
60Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
8 active — — —

Root Cause

DNS resolution fails at the cluster level because CoreDNS is down, misconfigured, or blocked by NetworkPolicy.

generic

Workarounds

  1. 92% success Check CoreDNS pod status and logs: kubectl get pods -n kube-system -l k8s-app=kube-dns 
    kubectl logs -n kube-system -l k8s-app=kube-dns — look for upstream DNS failures or loop detection

    Sources: https://kubernetes.io/docs/tasks/administer-cluster/dns-debugging-resolution/

  2. 85% success Check if NetworkPolicy blocks egress to kube-dns on port 53 
    Ensure egress NetworkPolicy allows UDP/TCP port 53 to kube-system namespace

    Sources: https://kubernetes.io/docs/tasks/administer-cluster/dns-debugging-resolution/

Dead Ends

Common approaches that don't work:

  1. Add custom /etc/hosts entries to all pods 85% fail

    Doesn't scale — service IPs change and new services won't be resolvable

  2. Restart all pods in the cluster 80% fail

    If CoreDNS is the problem, restarting app pods won't fix DNS

Error Chain

Leads to:
Preceded by:
Frequently confused with: