Coredns

CoreDNS is one of those quiet heroes in your Kubernetes cluster. It doesn’t get much attention—until DNS stops working, and suddenly everything breaks. Let’s understand how it works — simply. What Is CoreDNS? CoreDNS is the default DNS server in Kubernetes. It’s what helps your pods resolve names like my-service.default.svc.cluster.local to an actual IP address. It’s not just a DNS server. It’s modular, pluggable, and built for cloud-native environments. Why Is DNS Needed in Kubernetes? In Kubernetes, everything is dynamic: ...

Why Add a Custom DNS Zone? Adding a custom DNS zone in CoreDNS can be useful for: Internal testing (e.g., *.local or *.internal) Service discovery for non-Kubernetes services Custom mappings and overrides Step-by-Step Guide 1. Edit the CoreDNS ConfigMap kubectl -n kube-system edit configmap coredns Add a new zone block like this: apiVersion: v1 kind: ConfigMap metadata: name: coredns namespace: kube-system data: Corefile: | .:53 { errors health kubernetes cluster.local in-addr.arpa ip6.arpa { pods insecure fallthrough in-addr.arpa ip6.arpa } forward . /etc/resolv.conf cache 30 loop reload loadbalance } internal.test:53 { hosts { 10.10.10.10 service1.internal.test 10.10.10.11 service2.internal.test fallthrough } } 2. Restart CoreDNS kubectl -n kube-system rollout restart deployment coredns 3. Test the Zone From any pod: ...