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276 lines
7.8 KiB
276 lines
7.8 KiB
# Role-based Access Control
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In Kubernetes, granting a role to an application-specific service account is a best practice to ensure that your application is operating in the scope that you have specified. Read more about service account permissions [in the official Kubernetes docs](https://kubernetes.io/docs/admin/authorization/rbac/#service-account-permissions).
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Bitnami also has a fantastic guide for [configuring RBAC in your cluster](https://docs.bitnami.com/kubernetes/how-to/configure-rbac-in-your-kubernetes-cluster/) that takes you through RBAC basics.
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This guide is for users who want to restrict Tiller's capabilities to install resources to certain namespaces, or to grant a Helm client running access to a Tiller instance.
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## Tiller and Role-based Access Control
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You can add a service account to Tiller using the `--service-account <NAME>` flag while you're configuring Helm. As a prerequisite, you'll have to create a role binding which specifies a [role](https://kubernetes.io/docs/admin/authorization/rbac/#role-and-clusterrole) and a [service account](https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/) name that have been set up in advance.
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Once you have satisfied the pre-requisite and have a service account with the correct permissions, you'll run a command like this: `helm init --service-account <NAME>`
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### Example: Service account with cluster-admin role
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In `rbac-config.yaml`:
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```yaml
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apiVersion: v1
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kind: ServiceAccount
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metadata:
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name: tiller
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namespace: kube-system
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---
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apiVersion: rbac.authorization.k8s.io/v1
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kind: ClusterRoleBinding
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metadata:
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name: tiller
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roleRef:
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apiGroup: rbac.authorization.k8s.io
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kind: ClusterRole
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name: cluster-admin
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subjects:
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- kind: ServiceAccount
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name: tiller
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namespace: kube-system
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```
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_Note: The cluster-admin role is created by default in a Kubernetes cluster, so you don't have to define it explicitly._
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```console
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$ kubectl create -f rbac-config.yaml
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serviceaccount "tiller" created
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clusterrolebinding "tiller" created
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$ helm init --service-account tiller --history-max 200
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```
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### Example: Deploy Tiller in a namespace, restricted to deploying resources only in that namespace
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In the example above, we gave Tiller admin access to the entire cluster. You are not at all required to give Tiller cluster-admin access for it to work. Instead of specifying a ClusterRole or a ClusterRoleBinding, you can specify a Role and RoleBinding to limit Tiller's scope to a particular namespace.
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```console
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$ kubectl create namespace tiller-world
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namespace "tiller-world" created
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$ kubectl create serviceaccount tiller --namespace tiller-world
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serviceaccount "tiller" created
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```
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Define a Role that allows Tiller to manage all resources in `tiller-world` like in `role-tiller.yaml`:
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```yaml
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kind: Role
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: tiller-manager
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namespace: tiller-world
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rules:
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- apiGroups: ["", "batch", "extensions", "apps"]
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resources: ["*"]
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verbs: ["*"]
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```
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```console
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$ kubectl create -f role-tiller.yaml
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role "tiller-manager" created
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```
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In `rolebinding-tiller.yaml`,
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```yaml
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kind: RoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: tiller-binding
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namespace: tiller-world
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subjects:
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- kind: ServiceAccount
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name: tiller
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namespace: tiller-world
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roleRef:
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kind: Role
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name: tiller-manager
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apiGroup: rbac.authorization.k8s.io
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```
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```console
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$ kubectl create -f rolebinding-tiller.yaml
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rolebinding "tiller-binding" created
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```
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Afterwards you can run `helm init` to install Tiller in the `tiller-world` namespace.
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```console
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$ helm init --service-account tiller --tiller-namespace tiller-world
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$HELM_HOME has been configured at /Users/awesome-user/.helm.
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Tiller (the Helm server side component) has been installed into your Kubernetes Cluster.
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$ helm install nginx --tiller-namespace tiller-world --namespace tiller-world
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NAME: wayfaring-yak
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LAST DEPLOYED: Mon Aug 7 16:00:16 2017
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NAMESPACE: tiller-world
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STATUS: DEPLOYED
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RESOURCES:
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==> v1/Pod
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NAME READY STATUS RESTARTS AGE
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wayfaring-yak-alpine 0/1 ContainerCreating 0 0s
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```
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### Example: Deploy Tiller in a namespace, restricted to deploying resources in another namespace
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In the example above, we gave Tiller admin access to the namespace it was deployed inside. Now, let's limit Tiller's scope to deploy resources in a different namespace!
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For example, let's install Tiller in the namespace `myorg-system` and allow Tiller to deploy resources in the namespace `myorg-users`.
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```console
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$ kubectl create namespace myorg-system
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namespace "myorg-system" created
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$ kubectl create serviceaccount tiller --namespace myorg-system
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serviceaccount "tiller" created
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```
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Define a Role that allows Tiller to manage all resources in `myorg-users` like in `role-tiller.yaml`:
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```yaml
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kind: Role
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: tiller-manager
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namespace: myorg-users
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rules:
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- apiGroups: ["", "batch", "extensions", "apps"]
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resources: ["*"]
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verbs: ["*"]
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```
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```console
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$ kubectl create -f role-tiller.yaml
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role "tiller-manager" created
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```
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Bind the service account to that role. In `rolebinding-tiller.yaml`,
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```yaml
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kind: RoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: tiller-binding
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namespace: myorg-users
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subjects:
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- kind: ServiceAccount
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name: tiller
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namespace: myorg-system
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roleRef:
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kind: Role
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name: tiller-manager
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apiGroup: rbac.authorization.k8s.io
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```
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```console
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$ kubectl create -f rolebinding-tiller.yaml
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rolebinding "tiller-binding" created
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```
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We'll also need to grant Tiller access to read configmaps in myorg-system so it can store release information. In `role-tiller-myorg-system.yaml`:
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```yaml
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kind: Role
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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namespace: myorg-system
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name: tiller-manager
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rules:
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- apiGroups: ["", "extensions", "apps"]
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resources: ["configmaps"]
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verbs: ["*"]
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```
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```console
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$ kubectl create -f role-tiller-myorg-system.yaml
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role "tiller-manager" created
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```
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And the respective role binding. In `rolebinding-tiller-myorg-system.yaml`:
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```yaml
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kind: RoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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name: tiller-binding
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namespace: myorg-system
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subjects:
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- kind: ServiceAccount
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name: tiller
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namespace: myorg-system
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roleRef:
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kind: Role
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name: tiller-manager
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apiGroup: rbac.authorization.k8s.io
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```
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```console
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$ kubectl create -f rolebinding-tiller-myorg-system.yaml
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rolebinding "tiller-binding" created
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```
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## Helm and Role-based Access Control
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When running a Helm client in a pod, in order for the Helm client to talk to a Tiller instance, it will need certain privileges to be granted. Specifically, the Helm client will need to be able to create pods, forward ports and be able to list pods in the namespace where Tiller is running (so it can find Tiller).
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### Example: Deploy Helm in a namespace, talking to Tiller in another namespace
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In this example, we will assume Tiller is running in a namespace called `tiller-world` and that the Helm client is running in a namespace called `helm-world`. By default, Tiller is running in the `kube-system` namespace.
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In `helm-user.yaml`:
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```yaml
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apiVersion: v1
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kind: ServiceAccount
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metadata:
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name: helm
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namespace: helm-world
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---
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apiVersion: rbac.authorization.k8s.io/v1
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kind: Role
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metadata:
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name: tiller-user
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namespace: tiller-world
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rules:
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- apiGroups:
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- ""
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resources:
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- pods/portforward
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verbs:
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- create
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- apiGroups:
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- ""
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resources:
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- pods
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verbs:
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- list
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---
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apiVersion: rbac.authorization.k8s.io/v1
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kind: RoleBinding
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metadata:
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name: tiller-user-binding
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namespace: tiller-world
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roleRef:
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apiGroup: rbac.authorization.k8s.io
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kind: Role
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name: tiller-user
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subjects:
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- kind: ServiceAccount
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name: helm
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namespace: helm-world
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```
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```console
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$ kubectl create -f helm-user.yaml
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serviceaccount "helm" created
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role "tiller-user" created
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rolebinding "tiller-user-binding" created
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```
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