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| reviewers | title | min-kubernetes-server-version | content_template | |
|---|---|---|---|---|
|
Using CoreDNS for Service Discovery | v1.9 | templates/task |
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About CoreDNS
CoreDNS is a flexible, extensible DNS server that can serve as the Kubernetes cluster DNS. Like Kubernetes, the CoreDNS project is hosted by the CNCF.
You can use CoreDNS instead of kube-dns in your cluster by replacing kube-dns in an existing deployment, or by using tools like kubeadm that will deploy and upgrade the cluster for you.
Installing CoreDNS
For manual deployment or replacement of kube-dns, see the documentation at the CoreDNS GitHub project.
Upgrading an existing cluster with kubeadm
In Kubernetes version 1.10 and later, you can also move to CoreDNS when you use kubeadm to upgrade
a cluster that is using kube-dns. In this case, kubeadm will generate the CoreDNS configuration
("Corefile") based upon the kube-dns ConfigMap, preserving configurations for federation,
stub domains, and upstream name server.
If you are moving from kube-dns to CoreDNS, make sure to set the CoreDNS feature gate to true
during an upgrade. For example, here is what a v1.11.0 upgrade would look like:
kubeadm upgrade apply v1.11.0 --feature-gates=CoreDNS=true
In Kubernetes version 1.13 and later the CoreDNS feature gate is removed and CoreDNS
is used by default. Follow the guide outlined here if you want
your upgraded cluster to use kube-dns.
In versions prior to 1.11 the Corefile will be overwritten by the one created during upgrade. You should save your existing ConfigMap if you have customized it. You may re-apply your customizations after the new ConfigMap is up and running.
If you are running CoreDNS in Kubernetes version 1.11 and later, during upgrade, your existing Corefile will be retained.
Installing kube-dns instead of CoreDNS with kubeadm
{{< note >}} In Kubernetes 1.11, CoreDNS has graduated to General Availability (GA) and is installed by default. {{< /note >}}
To install kube-dns on versions prior to 1.13, set the CoreDNS feature gate
value to false:
kubeadm init --feature-gates=CoreDNS=false
For versions 1.13 and later, follow the guide outlined here.
Tuning CoreDNS
When resource utilisation is a concern, it may be useful to tune the configuration of CoreDNS. For more details, check out the documentation on scaling CoreDNS.
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You can configure CoreDNS to support many more use cases than
kube-dns by modifying the Corefile. For more information, see the
CoreDNS site.
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