# Outline

This example describes how to create Web frontend server, an auto-provisioned persistent volume on GCE, and an NFS-backed persistent claim.

Demonstrated Kubernetes Concepts:

* [Persistent Volumes](http://kubernetes.io/docs/user-guide/persistent-volumes/) to
  define persistent disks (disk lifecycle not tied to the Pods).
* [Services](http://kubernetes.io/docs/user-guide/services/) to enable Pods to
  locate one another.

![alt text][nfs pv example]

As illustrated above, two persistent volumes are used in this example:

- Web frontend Pod uses a persistent volume based on NFS server, and
- NFS server uses an auto provisioned [persistent volume](http://kubernetes.io/docs/user-guide/persistent-volumes/) from GCE PD or AWS EBS.

Note, this example uses an NFS container that doesn't support NFSv4.

[nfs pv example]: nfs-pv.png


## Quickstart

```console
$ kubectl create -f examples/volumes/nfs/provisioner/nfs-server-gce-pv.yaml
$ kubectl create -f examples/volumes/nfs/nfs-server-rc.yaml
$ kubectl create -f examples/volumes/nfs/nfs-server-service.yaml
# get the cluster IP of the server using the following command
$ kubectl describe services nfs-server
# use the NFS server IP to update nfs-pv.yaml and execute the following
$ kubectl create -f examples/volumes/nfs/nfs-pv.yaml
$ kubectl create -f examples/volumes/nfs/nfs-pvc.yaml
# run a fake backend
$ kubectl create -f examples/volumes/nfs/nfs-busybox-rc.yaml
# get pod name from this command
$ kubectl get pod -l name=nfs-busybox
# use the pod name to check the test file
$ kubectl exec nfs-busybox-jdhf3 -- cat /mnt/index.html
```

## Example of NFS based persistent volume

See [NFS Service and Replication Controller](nfs-web-rc.yaml) for a quick example of how to use an NFS
volume claim in a replication controller. It relies on the
[NFS persistent volume](nfs-pv.yaml) and
[NFS persistent volume claim](nfs-pvc.yaml) in this example as well.

## Complete setup

The example below shows how to export a NFS share from a single pod replication
controller and import it into two replication controllers.

### NFS server part

Define [the NFS Service and Replication Controller](nfs-server-rc.yaml) and
[NFS service](nfs-server-service.yaml):

The NFS server exports an an auto-provisioned persistent volume backed by GCE PD:

```console
$ kubectl create -f examples/volumes/nfs/provisioner/nfs-server-gce-pv.yaml
```

```console
$ kubectl create -f examples/volumes/nfs/nfs-server-rc.yaml
$ kubectl create -f examples/volumes/nfs/nfs-server-service.yaml
```

The directory contains dummy `index.html`. Wait until the pod is running
by checking `kubectl get pods -l role=nfs-server`.

### Create the NFS based persistent volume claim

The [NFS busybox controller](nfs-busybox-rc.yaml) uses a simple script to
generate data written to the NFS server we just started. First, you'll need to
find the cluster IP of the server:

```console
$ kubectl describe services nfs-server
```

Replace the invalid IP in the [nfs PV](nfs-pv.yaml). (In the future,
we'll be able to tie these together using the service names, but for
now, you have to hardcode the IP.)

Create the the [persistent volume](../../../docs/user-guide/persistent-volumes.md)
and the persistent volume claim for your NFS server. The persistent volume and
claim gives us an indirection that allow multiple pods to refer to the NFS
server using a symbolic name rather than the hardcoded server address.

```console
$ kubectl create -f examples/volumes/nfs/nfs-pv.yaml
$ kubectl create -f examples/volumes/nfs/nfs-pvc.yaml
```

## Setup the fake backend

The [NFS busybox controller](nfs-busybox-rc.yaml) updates `index.html` on the
NFS server every 10 seconds. Let's start that now:

```console
$ kubectl create -f examples/volumes/nfs/nfs-busybox-rc.yaml
```

Conveniently, it's also a `busybox` pod, so we can get an early check
that our mounts are working now. Find a busybox pod and exec:

```console
$ kubectl get pod -l name=nfs-busybox
NAME                READY     STATUS    RESTARTS   AGE
nfs-busybox-jdhf3   1/1       Running   0          25m
nfs-busybox-w3s4t   1/1       Running   0          25m
$ kubectl exec nfs-busybox-jdhf3 -- cat /mnt/index.html
Thu Oct 22 19:20:18 UTC 2015
nfs-busybox-w3s4t
```

You should see output similar to the above if everything is working well. If
it's not, make sure you changed the invalid IP in the [NFS PV](nfs-pv.yaml) file
and make sure the `describe services` command above had endpoints listed
(indicating the service was associated with a running pod).

### Setup the web server

The [web server controller](nfs-web-rc.yaml) is an another simple replication
controller demonstrates reading from the NFS share exported above as a NFS
volume and runs a simple web server on it.

Define the pod:

```console
$ kubectl create -f examples/volumes/nfs/nfs-web-rc.yaml
```

This creates two pods, each of which serve the `index.html` from above. We can
then use a simple service to front it:

```console
kubectl create -f examples/volumes/nfs/nfs-web-service.yaml
```

We can then use the busybox container we launched before to check that `nginx`
is serving the data appropriately:

```console
$ kubectl get pod -l name=nfs-busybox
NAME                READY     STATUS    RESTARTS   AGE
nfs-busybox-jdhf3   1/1       Running   0          1h
nfs-busybox-w3s4t   1/1       Running   0          1h
$ kubectl get services nfs-web
NAME      LABELS    SELECTOR            IP(S)        PORT(S)
nfs-web   <none>    role=web-frontend   10.0.68.37   80/TCP
$ kubectl exec nfs-busybox-jdhf3 -- wget -qO- http://10.0.68.37
Thu Oct 22 19:28:55 UTC 2015
nfs-busybox-w3s4t
```




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