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coredns: update notes in administer-cluster/coredns.md #8697

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May 25, 2018
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coredns: update notes in administer-cluster/coredns.md #8697

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37 changes: 18 additions & 19 deletions content/en/docs/tasks/administer-cluster/coredns.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,11 +6,8 @@ min-kubernetes-server-version: v1.9
content_template: templates/task
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Is the min-kubernetes-server-version still correct for these updates?

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yes, the minimum version in this case is 1.9 when CoreDNS was introduced as alpha:
we are removing the following text from the file - In Kubernetes 1.9, [CoreDNS](https://coredns.io) is available as an alpha feature

---

{{< feature-state state="beta" >}}

{{% capture overview %}}
This page describes how to enable CoreDNS instead of kube-dns for service
discovery.
This page describes the CoreDNS upgrade process and how to install kube-dns instead of CoreDNS.
{{% /capture %}}

{{% capture prerequisites %}}
Expand All @@ -19,32 +16,34 @@ discovery.

{{% capture steps %}}

## Installing CoreDNS with kubeadm

In Kubernetes 1.9, [CoreDNS](https://coredns.io) is available as an alpha feature, and
in Kubernetes 1.10 it is available as a beta feature. In either case, you may install
it during cluster creation by setting the `CoreDNS` feature gate to `true` during `kubeadm init`:
## Installing kube-dns with kubeadm

In Kubernetes 1.11, [CoreDNS](https://coredns.io) has graduated to General Availability (GA)
and is installed by default. To install kube-dns instead, set the `CoreDNS` feature gate
value to `false`:
```
kubeadm init --feature-gates=CoreDNS=true
kubeadm init --feature-gates=CoreDNS=false
```

This installs CoreDNS instead of kube-dns.

## Upgrading an Existing Cluster with kubeadm

In Kubernetes 1.10, you can also move to CoreDNS when you use `kubeadm` to upgrade
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
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Can you add a line to clarify that we need to set the CoreDNS feature-gates to true
kubeadm upgrade apply v1.11.0 --feature-gates=CoreDNS=true when moving from kube-dns to CoreDNS during an upgrade.

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sure.

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Is this done?

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yes.

("Corefile") based upon the `kube-dns` ConfigMap, preserving configurations for federation,
stub domains, and upstream name server.

Note that if you are running CoreDNS in your cluster already, prior to upgrade, your existing 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 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 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.

This process will be modified for the GA release of this feature, such that an existing
Corefile will not be overwritten.
If you are running CoreDNS in Kubernetes version 1.11 and later, during upgrade,
your existing Corefile will be retained.

{{% /capture %}}

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