Merge pull request #2761 from michelleN/service-account-docs

chore(docs): add guide for service accounts

docs/service_accounts.md

+# Tiller and Service Accounts
+
+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). 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.
+
+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.
+
+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>`
+
+## Example: Service account with cluster-admin role
+
+```console
+$ kubectl create serviceaccount tiller --namespace kube-system
+```
+
+In `rbac-config.yaml`:
+```yaml
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: tiller
+  namespace: kube-system
+---
+apiVersion: rbac.authorization.k8s.io/v1beta1
+kind: ClusterRoleBinding
+metadata:
+  name: tiller
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: cluster-admin
+subjects:
+  - kind: ServiceAccount
+    name: tiller
+    namespace: kube-system
+```
+
+_Note: The cluster-admin role is created by default in a Kubernetes cluster, so you don't have to define it explicitly._
+
+```console
+$ kubectl create -f rbac-config.yaml
+$ helm init --service-account tiller
+```
+
+## Example: Service account restricted to a namespace
+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.
+
+```console
+$ kubectl create namespace tiller-world
+namespace "tiller-world" created
+$ kubectl create serviceaccount tiller --namespace tiller-world
+serviceaccount "tiller" created
+```
+
+Define a Role like in `role-tiller.yaml`:
+```yaml
+kind: Role
+apiVersion: rbac.authorization.k8s.io/v1beta1
+metadata:
+  namespace: tiller-world
+  name: tiller-manager
+rules:
+- apiGroups: ["", "extensions", "apps"]
+  resources: ["deployments", "replicasets", "pods", "configmaps", "secrets", "namespaces"]
+  verbs: ["get", "list", "watch", "create", "update", "patch", "delete"] # You can also use ["*"]
+```
+
+```console
+$ kubectl create -f role-tiller.yaml
+role "tiller-manager" created
+```
+
+In `rolebinding-tiller.yaml`,
+```yaml
+kind: RoleBinding
+apiVersion: rbac.authorization.k8s.io/v1beta1
+metadata:
+  name: tiller-binding
+  namespace: tiller-world
+subjects:
+- kind: ServiceAccount
+  name: tiller
+  namespace: tiller-world
+roleRef:
+  kind: Role
+  name: tiller-manager
+  apiGroup: rbac.authorization.k8s.io
+```
+
+```console
+$ kubectl create -f rolebinding-tiller.yaml
+rolebinding "tiller-binding" created
+```
+
+```console
+$ helm init --service-account tiller --tiller-namespace tiller-world
+$HELM_HOME has been configured at /Users/awesome-user/.helm.
+
+Tiller (the helm server side component) has been installed into your Kubernetes Cluster.
+Happy Helming!
+
+$ helm install nginx --tiller-namespace tiller-world --namespace tiller-world
+NAME:   wayfaring-yak
+LAST DEPLOYED: Mon Aug  7 16:00:16 2017
+NAMESPACE: tiller-world
+STATUS: DEPLOYED
+
+RESOURCES:
+==> v1/Pod
+NAME                  READY  STATUS             RESTARTS  AGE
+wayfaring-yak-alpine  0/1    ContainerCreating  0         0s
+```
+

docs/using_helm.md

@@ -494,7 +494,7 @@ accepts chart source code, and (after audit) packages those for you.
 In some cases you may wish to scope Tiller or deploy multiple Tillers to a single cluster. Here are some best practices when operating in those circumstances.
 
 1. Tiller can be [installed](install.md) into any namespace. By default, it is installed into kube-system. You can run multiple Tillers provided they each run in their own namespace.
-2. Limiting Tiller to only be able to install into specific namespaces and/or resource types is controlled by Kubernetes [RBAC](https://kubernetes.io/docs/admin/authorization/rbac/) roles and rolebindings.
+2. Limiting Tiller to only be able to install into specific namespaces and/or resource types is controlled by Kubernetes [RBAC](https://kubernetes.io/docs/admin/authorization/rbac/) roles and rolebindings. You can add a service account to Tiller when configuring Helm via `helm init --service-acount <NAME>`. You can find more information about that [here](service_accounts.md).
 3. Release names are unique PER TILLER INSTANCE.
 4. Charts should only contain resources that exist in a single namespace.
 5. It is not recommended to have multiple Tillers configured to manage resources in the same namespace.