• k8s
• k8sDNS

k8s DNS

• Pods & Services

  • Services.

    • DNS: <Hostname>.<Namespace>.<Type>.<Root=cluster.local>

      • e.g. web-service.appsNs.svc.cluster.local
  • Pods, do not get dns entries by default, can be enabled.

    • If pod dns enabled, creates record from ip 10.244.2.5 -> 10-244-2-5.appsNs.pod.cluster.local

  • In same namespace web-service.
  • In apps namespace apps.web-service
• in container, /etc/resolve.conf, has k8s dns server as nameserver
  • kubelet launches pods and does the /etc/resolve.conf setup.

    • adds to /etc/resolve.conf nameserver and for ns=default e.g search default.svc.cluster.local svc.cluster.local cluster.local

• CoreDNS (Service kube-dns)
  • From v1.12 CoreDNS used for dns, deployed as pod in -n kube-system

    • config /etc/coredns/Corefile, passed into pod as configmap coredns.

    • uses plugins

Core DNS logs

• NXDOMAIN (Non-Existent Domain):
  • The queried domain name does not exist in the DNS zone.
• NOERROR (No Error):
  • The DNS query was successful