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Merge pull request #1788 from nikhiljindal/dnsDoc

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Updating information on how to pass federations flag to kube-dns
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devin-donnelly
2016-12-06 17:23:27 -08:00
committed by GitHub
parent d39d03c1fa e6d09b57fc
commit 0cd2ea763c
1 changed files with 55 additions and 21 deletions
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@@ -14,11 +14,11 @@ This guide explains how to set up cluster federation that lets us control multip
## Prerequisites
This guide assumes that you have a running Kubernetes cluster.
If not, then head over to the [getting started guides](/docs/getting-started-guides/) to bring up a cluster.
If you need to start a new cluster, see the [getting started guides](/docs/getting-started-guides/) for instructions on bringing a cluster up.
This guide also assumes that you have a Kubernetes release
[downloaded from here](/docs/getting-started-guides/binary_release/),
extracted into a directory and all the commands in this guide are run from
To use the commands in this guide, you must download a Kubernetes release from the
[getting started binary releases](/docs/getting-started-guides/binary_release/) and
extract into a directory; all the commands in this guide are run from
that directory.
```shell
@@ -26,8 +26,8 @@ $ curl -L https://github.com/kubernetes/kubernetes/releases/download/v1.4.0/kube
$ cd kubernetes
```
This guide also assumes that you have an installation of Docker running
locally, i.e. on the machine where you run the commands described in this
You must also have a Docker installation running
locally--meaning on the machine where you run the commands described in this
guide.
## Setting up a federation control plane
@@ -212,47 +212,81 @@ cluster1 Ready 3m
## Updating KubeDNS
Once the cluster is registered with the federation, you are all set to use it.
But for the cluster to be able to route federation service requests, you need to restart
KubeDNS and pass it a `--federations` flag which tells it about valid federation DNS hostnames.
Format of the flag is like this:
Once you've registered your cluster with the federation, you'll need to update KubeDNS so that your cluster can route federation service requests. The update method varies depending on your Kubernetes version; on Kubernetes 1.5 or later, you must pass the
`--federations` flag to kube-dns via the kube-dns config map. In version 1.4 or earlier, you must set the `--federations` flag directly on kube-dns-rc on other clusters.
### Kubernetes 1.5+: Passing federations flag via config map to kube-dns
For kubernetes clusters of version 1.5+, you can pass the
`--federations` flag to kube-dns via the kube-dns config map.
The flag uses the following format:
```
--federations=${FEDERATION_NAME}=${DNS_DOMAIN_NAME}
```
To update KubeDNS with federations flag, you can edit the existing kubedns replication controller to
include that flag in pod template spec and then delete the existing pod. Replication controller will
recreate the pod with updated template.
To pass this flag to KubeDNS, create a config-map with name `kube-dns` in
namespace `kube-system`. The configmap should look like the following:
To find the name of existing kubedns replication controller, run
```yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: kube-dns
namespace: kube-system
data:
federations: <federation-name>=<dns-domain-name>
```
where `<federation-name>` should be replaced by the name you want to give to your
federation, and
`federation-domain-name` should be replaced by the domain name you want to use
in your federation DNS.
You can find more details about config maps in general at
http://kubernetes.io/docs/user-guide/configmap/.
### Kubernetes 1.4 and earlier: Setting federations flag on kube-dns-rc
If your cluster is running Kubernetes version 1.4 or earlier, you must to restart
KubeDNS and pass it a `--federations` flag, which tells it about valid federation DNS hostnames.
The flag uses the following format:
```
--federations=${FEDERATION_NAME}=${DNS_DOMAIN_NAME}
```
To update KubeDNS with the `--federations` flag, you can edit the existing kubedns replication controller to
include that flag in pod template spec, and then delete the existing pod. The replication controller then
recreates the pod with updated template.
To find the name of existing kubedns replication controller, run the following command:
```shell
$ kubectl get rc --namespace=kube-system
```
This will list all the replication controllers. Name of the kube-dns replication
controller will look like `kube-dns-v18`. You can then edit it by running:
You should see a list of all the replication controllers on the cluster. The kube-dns replication
controller should have a name similar to `kube-dns-v18`. To edit the replication controller, specify it by name as follows:
```shell
$ kubectl edit rc <rc-name> --namespace=kube-system
```
Add the `--federations` flag as args to kube-dns container in the YAML file that
pops up after running the above command.
In the resulting YAML file for the kube-dns replication controller, add the `--federations` flag as an argument to kube-dns container.
To delete the existing kube dns pod, you can first find it by running:
Then, you must delete the existing kube dns pod. You can find the pod by running:
```shell
$ kubectl get pods --namespace=kube-system
```
And then delete it by running:
And then delete the appropriate pod by running:
```shell
$ kubectl delete pods <pod-name> --namespace=kube-system
```
You are now all set to start using federation.
Once you've completed the kube-dns configuration, your federation is ready for use.
## Turn down