In our previous post, we showed how CoreDNS can be used in place of Kube-DNS for service discovery in Kubernetes clusters. In that blog, there is a footnote about issues trying to replace Kube-DNS when using Google Container Engine (GKE). As it so happens, there is a similar issue with minikube, which is a local Kubernetes environment that is very useful for developers.
When you try to replace Kube-DNS, you will find that shortly after you modify its service to point to CoreDNS, your changes will be reverted. This is because Minikube has an addon manager that periodically verifies the configuration state of any installed addons, and Kube-DNS is one of those addons.
Luckily, this is really easy to solve for Minikube. The
minikube command allows you to modify the installed
plugins for Minikube. So, we simply need to disable the
kube-dns addon before running our
kubectl apply -f
that is described in the previous blog:
$ minikube addons list - dashboard: enabled - default-storageclass: enabled - kube-dns: enabled - heapster: disabled - ingress: disabled - registry-creds: disabled - addon-manager: enabled $ minikube addons disable kube-dns kube-dns was successfully disabled $ minikube addons list - heapster: disabled - ingress: disabled - registry-creds: disabled - addon-manager: enabled - dashboard: enabled - default-storageclass: enabled - kube-dns: disabled
Now we can apply the
coredns.yaml, and also delete the
will not be automatically deleted by disabling the addon.
$ kubectl apply -f coredns.yaml serviceaccount "coredns" configured clusterrole "system:coredns" configured clusterrolebinding "system:coredns" configured configmap "coredns" configured deployment "coredns" configured service "kube-dns" configured $ kubectl get -n kube-system pods NAME READY STATUS RESTARTS AGE coredns-980047985-g2748 1/1 Running 1 36m kube-addon-manager-minikube 1/1 Running 0 9d kube-dns-v20-qzvr2 3/3 Running 0 1m kubernetes-dashboard-ks1jp 1/1 Running 0 9d $ kubectl delete -n kube-system rc kube-dns-v20 replicationcontroller "kube-dns-v20" deleted $
And there we have it, CoreDNS is up and running and won’t be overwritten by the addon manager.