coredns-deployment/kubernetes

Kubernetes

CoreDNS can run in place of the standard Kube-DNS in Kubernetes. Using the kubernetes plugin, CoreDNS will read zone data from a Kubernetes cluster. It implements the spec defined for Kubernetes DNS-Based service discovery:

https://github.com/kubernetes/dns/blob/master/docs/specification.md

deploy.sh and coredns.yaml.sed

deploy.sh is a convenience script to generate a manifest for running CoreDNS on a cluster that is currently running standard kube-dns. Using the coredns.yaml.sed file as a template, it creates a ConfigMap and a CoreDNS deployment, then updates the Kube-DNS service selector to use the CoreDNS deployment. By re-using the existing service, there is no disruption in servicing requests.

The script doesn't delete the kube-dns deployment or replication controller - you'll have to do that manually, after deploying CoreDNS.

You should examine the manifest carefully and make sure it is correct for your particular cluster. Depending on how you have built your cluster and the version you are running, some modifications to the manifest may be needed.

In the best case scenario, all that's needed to replace Kube-DNS are these two commands:

$ ./deploy.sh | kubectl apply -f -
$ kubectl delete --namespace=kube-system deployment kube-dns

NOTE: It is recommended to delete the kube-dns deployment. Otherwise, if both CoreDNS and kube-dns are running, queries may randomly hit either CoreDNS or kube-dns.

For non-RBAC deployments, you'll need to edit the resulting yaml before applying it:

1. Remove the line serviceAccountName: coredns from the Deployment section.
2. Remove the ServiceAccount, ClusterRole, and ClusterRoleBinding sections.