Multi-cluster services documentation, take II
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Prashanth Balasubramanian
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<!-- BEGIN MUNGE: UNVERSIONED_WARNING -->
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<!-- BEGIN STRIP_FOR_RELEASE -->
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<img src="http://kubernetes.io/img/warning.png" alt="WARNING"
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width="25" height="25">
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<h2>PLEASE NOTE: This document applies to the HEAD of the source tree</h2>
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If you are using a released version of Kubernetes, you should
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refer to the docs that go with that version.
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<strong>
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The latest 1.0.x release of this document can be found
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[here](http://releases.k8s.io/release-1.0/examples/sharing-clusters/README.md).
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Documentation for other releases can be found at
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[releases.k8s.io](http://releases.k8s.io).
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</strong>
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--
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<!-- END STRIP_FOR_RELEASE -->
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<!-- END MUNGE: UNVERSIONED_WARNING -->
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# Sharing Clusters
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This example demonstrates how to access one kubernetes cluster from another. It only works if both clusters are running on the same network, on a cloud provider that provides a private ip range per network (eg: GCE, GKE, AWS).
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## Setup
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Create a cluster in US (you don't need to do this if you already have a running kubernetes cluster)
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```shell
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$ cluster/kube-up.sh
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```
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Before creating our second cluster, lets have a look at the kubectl config:
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```yaml
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apiVersion: v1
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clusters:
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- cluster:
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certificate-authority-data: REDACTED
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server: https://104.197.84.16
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name: <clustername_us>
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...
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current-context: <clustername_us>
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...
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```
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Now spin up the second cluster in Europe
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```shell
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$ ./cluster/kube-up.sh
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$ KUBE_GCE_ZONE=europe-west1-b KUBE_GCE_INSTANCE_PREFIX=eu ./cluster/kube-up.sh
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```
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Your kubectl config should contain both clusters:
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```yaml
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apiVersion: v1
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clusters:
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- cluster:
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certificate-authority-data: REDACTED
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server: https://146.148.25.221
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name: <clustername_eu>
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- cluster:
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certificate-authority-data: REDACTED
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server: https://104.197.84.16
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name: <clustername_us>
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...
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current-context: kubernetesdev_eu
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...
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```
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And kubectl get nodes should agree:
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```
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$ kubectl get nodes
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NAME LABELS STATUS
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eu-minion-0n61 kubernetes.io/hostname=eu-minion-0n61 Ready
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eu-minion-79ua kubernetes.io/hostname=eu-minion-79ua Ready
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eu-minion-7wz7 kubernetes.io/hostname=eu-minion-7wz7 Ready
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eu-minion-loh2 kubernetes.io/hostname=eu-minion-loh2 Ready
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$ kubectl config use-context <clustername_us>
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$ kubectl get nodes
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NAME LABELS STATUS
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kubernetes-minion-5jtd kubernetes.io/hostname=kubernetes-minion-5jtd Ready
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kubernetes-minion-lqfc kubernetes.io/hostname=kubernetes-minion-lqfc Ready
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kubernetes-minion-sjra kubernetes.io/hostname=kubernetes-minion-sjra Ready
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kubernetes-minion-wul8 kubernetes.io/hostname=kubernetes-minion-wul8 Ready
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```
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## Testing reachability
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For this test to work we'll need to create a service in europe:
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```
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$ kubectl config use-context <clustername_eu>
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$ kubectl create -f /tmp/secret.json
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$ kubectl create -f examples/https-nginx/nginx-app.yaml
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$ kubectl exec -it my-nginx-luiln -- echo "Europe nginx" >> /usr/share/nginx/html/index.html
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$ kubectl get ep
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NAME ENDPOINTS
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kubernetes 10.240.249.92:443
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nginxsvc 10.244.0.4:80,10.244.0.4:443
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```
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Just to test reachability, we'll try hitting the Europe nginx from our initial US central cluster. Create a basic curl pod in the US cluster:
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```yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: curlpod
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spec:
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containers:
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- image: radial/busyboxplus:curl
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command:
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- sleep
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- "360000000"
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imagePullPolicy: IfNotPresent
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name: curlcontainer
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restartPolicy: Always
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```
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And test that you can actually reach the test nginx service across continents
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```
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$ kubectl config use-context <clustername_us>
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$ kubectl -it exec curlpod -- /bin/sh
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[ root@curlpod:/ ]$ curl http://10.244.0.4:80
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Europe nginx
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```
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## Granting access to the remote cluster
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We will grant the US cluster access to the Europe cluster. Basically we're going to setup a secret that allows kubectl to function in a pod running in the US cluster, just like it did on our local machine in the previous step. First create a secret with the contents of the current .kube/config:
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```shell
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$ kubectl config use-context <clustername_eu>
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$ go run ./make_secret.go --kubeconfig=$HOME/.kube/config > /tmp/secret.json
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$ kubectl config use-context <clustername_us>
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$ kubectl create -f /tmp/secret.json
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```
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Create a kubectl pod that uses the secret, in the US cluster.
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```json
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{
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"kind": "Pod",
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"apiVersion": "v1",
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"metadata": {
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"name": "kubectl-tester"
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},
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"spec": {
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"volumes": [
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{
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"name": "secret-volume",
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"secret": {
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"secretName": "kubeconfig"
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}
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}
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],
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"containers": [
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{
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"name": "kubectl",
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"image": "bprashanth/kubectl:0.0",
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"imagePullPolicy": "Always",
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"env": [
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{
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"name": "KUBECONFIG",
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"value": "/.kube/config"
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}
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],
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"args": [
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"proxy", "-p", "8001"
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],
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"volumeMounts": [
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{
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"name": "secret-volume",
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"mountPath": "/.kube"
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}
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]
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}
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]
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}
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}
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```
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And check that you can access the remote cluster
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```shell
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$ kubectl config use-context <clustername_us>
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$ kubectl exec -it kubectl-tester bash
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kubectl-tester $ kubectl get nodes
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NAME LABELS STATUS
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eu-minion-0n61 kubernetes.io/hostname=eu-minion-0n61 Ready
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eu-minion-79ua kubernetes.io/hostname=eu-minion-79ua Ready
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eu-minion-7wz7 kubernetes.io/hostname=eu-minion-7wz7 Ready
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eu-minion-loh2 kubernetes.io/hostname=eu-minion-loh2 Ready
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```
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For a more advanced example of sharing clusters, see the [service-loadbalancer](../../contrib/service-loadbalancer/README.md)
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<!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
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[]()
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<!-- END MUNGE: GENERATED_ANALYTICS -->
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@ -0,0 +1,63 @@
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/*
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Copyright 2015 The Kubernetes Authors All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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// A tiny script to help conver a given kubeconfig into a secret.
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package main
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import (
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"flag"
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"fmt"
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"io/ioutil"
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"log"
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"k8s.io/kubernetes/pkg/api"
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"k8s.io/kubernetes/pkg/api/latest"
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"k8s.io/kubernetes/pkg/runtime"
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)
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// TODO:
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// Add a -o flag that writes to the specified destination file.
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var (
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kubeconfig = flag.String("kubeconfig", "", "path to kubeconfig file.")
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name = flag.String("name", "kubeconfig", "name to use in the metadata of the secret.")
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ns = flag.String("ns", "default", "namespace of the secret.")
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)
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func read(file string) []byte {
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b, err := ioutil.ReadFile(file)
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if err != nil {
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log.Fatalf("Cannot read file %v, %v", file, err)
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}
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return b
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}
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func main() {
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flag.Parse()
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if *kubeconfig == "" {
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log.Fatalf("Need to specify --kubeconfig")
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}
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cfg := read(*kubeconfig)
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secret := &api.Secret{
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ObjectMeta: api.ObjectMeta{
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Name: *name,
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Namespace: *ns,
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},
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Data: map[string][]byte{
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"config": cfg,
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},
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}
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fmt.Printf(runtime.EncodeOrDie(latest.Codec, secret))
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}
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