In-cluster DNS smoke test troubleshooting
Throwaway pod to resolve in-cluster names; verifies CoreDNS + kube-dns svc
kubectl run dnsutils --image=tutum/dnsutils -it --rm --restart=Never -- nslookup kubernetes.default
more troubleshooting
all 32 commands →
Query CoreDNS directly
dig +short @$(kubectl -n kube-system get svc kube-dns -o jsonpath='{.spec.clusterIP}') <name>.<ns>.svc.cluster.local
Inspect CoreDNS config and logs
kubectl -n kube-system get cm coredns -o yaml; kubectl -n kube-system logs deploy/coredns --tail=50
TLS cipher and protocol enum
nmap --script ssl-enum-ciphers -p 443 <host>
Verify full TLS chain and SNI
openssl s_client -connect <host>:443 -servername <host> -showcerts 2>/dev/null | grep -E 'Verify|s:|i:'
Batch cert expiry scan
for h in $(cat hosts.txt); do echo -n "$h "; echo | openssl s_client -connect $h:443 -servername $h 2>/dev/null | openssl x509 -noout -enddate; done