Updated self-hosting documentation (#13866)

* updated self-hosting documentation * removed more referances * updated wording * updated self-hosting warning to be more clear about the effects of pivot has on your cluster * Update content/en/docs/setup/independent/self-hosting.md Co-Authored-By: Klaven <mcounts@suse.com>
2019-05-07 14:30:41 -04:00
parent 99ae92bdf9
commit a1f811d852
5 changed files with 66 additions and 73 deletions
@@ -44,7 +44,6 @@ but you may also build them from source for other OSes.
 | kubeadm alpha subcommands | alpha          |
 | High availability         | alpha          |
 | DynamicKubeletConfig      | alpha          |
-| Self-hosting              | alpha          |


 kubeadm's overall feature state is **GA**. Some sub-features, like the configuration
@@ -0,0 +1,63 @@
+---
+reviewers:
+- sig-cluster-lifecycle
+title: Configuring your kubernetes cluster to self-host the control plane
+content_template: templates/concept
+weight: 100
+---
+
+{{% capture overview %}}
+
+### Self-hosting the Kubernetes control plane {#self-hosting}
+
+As of 1.8, you can experimentally create a _self-hosted_ Kubernetes control
+plane. This means that key components such as the API server, controller
+manager, and scheduler run as [DaemonSet pods](/docs/concepts/workloads/controllers/daemonset/)
+configured via the Kubernetes API instead of [static pods](/docs/tasks/administer-cluster/static-pod/)
+configured in the kubelet via static files.
+
+To create a self-hosted cluster see the `kubeadm alpha selfhosting pivot` command.
+
+#### Caveats
+
+{{< caution >}}
+This feature pivots your cluster into an unsupported state, rendering kubeadm unable
+to manage you cluster any longer. This includes `kubeadm upagrade`.
+{{< /caution >}}
+
+1. Self-hosting in 1.8 and later has some important limitations. In particular, a
+  self-hosted cluster _cannot recover from a reboot of the control-plane node_
+  without manual intervention.
+
+1. By default, self-hosted control plane Pods rely on credentials loaded from
+  [`hostPath`](https://kubernetes.io/docs/concepts/storage/volumes/#hostpath)
+  volumes. Except for initial creation, these credentials are not managed by
+  kubeadm.
+
+1. The self-hosted portion of the control plane does not include etcd,
+  which still runs as a static Pod.
+
+#### Process
+
+The self-hosting bootstrap process is documented in the [kubeadm design
+document](https://github.com/kubernetes/kubeadm/blob/master/docs/design/design_v1.9.md#optional-self-hosting).
+
+In summary, `kubeadm alpha selfhosting` works as follows:
+
+  1. Waits for this bootstrap static control plane to be running and
+    healthy. This is identical to the `kubeadm init` process without self-hosting.
+
+  1. Uses the static control plane Pod manifests to construct a set of
+    DaemonSet manifests that will run the self-hosted control plane.
+    It also modifies these manifests where necessary, for example adding new volumes
+    for secrets.
+
+  1. Creates DaemonSets in the `kube-system` namespace and waits for the
+     resulting Pods to be running.
+
+  1. Once self-hosted Pods are operational, their associated static Pods are deleted
+     and kubeadm moves on to install the next component. This triggers kubelet to
+     stop those static Pods.
+
+  1. When the original static control plane stops, the new self-hosted control
+    plane is able to bind to listening ports and become active.