Q: DNS resolution is failing inside your cluster. Pods can't resolve service names. What do you check?
1. kubectl get pods -n kube-system | grep coredns — is CoreDNS running?
#Kubernetes #Networking #L2 #Container Orchestration #K8s
🎙️ Candidate Opening & Architectural Context
""In one of our high-traffic production clusters, our SRE team handled this incident using a standardized runbook. When addressing this question, I walk the interviewer through our production incident runbook: isolating the blast radius, checking diagnostic logs and metrics, and applying a safe fix.""
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🛠️ Production Runbook & Step-by-Step Resolution
1️⃣
Initial Diagnostics & Root Cause Analysis
kubectl get pods -n kube-system | grep coredns— is CoreDNS running?kubectl logs -n kube-system— any errors?- Test DNS from inside a pod:
kubectl exec -it— this should always resolve.-- nslookup kubernetes.default
2️⃣
Remediation & Permanent Safeguards
## 🟡 Storage
- Check
resolv.confinside the pod:kubectl exec -it— should point to the cluster DNS IP.-- cat /etc/resolv.conf - Check CoreDNS ConfigMap:
kubectl get configmap coredns -n kube-system -o yaml— misconfigured forwarders can break external DNS resolution.
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: kubectl get pods -n kube-system | grep coredns — is CoreDNS running?."
⚡ 60-Second Elevator Pitch Talking Points
- kubectl get pods -n kube-system | grep coredns — is CoreDNS running?
- kubectl logs -n kube-system — any errors?
- Test DNS from inside a pod: kubectl exec -it -- nslookup kubernetes.default — this should always...
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