Add example

tile-generator.html.md.erb

@@ -521,10 +521,10 @@ in a Pivotal Cloud Foundry (PCF) environment. [Helm](https://helm.sh/) is a conv
 package Kubernetes services.
 
 Tile Generator provides a convenient way to package your Helm Chart, along with 
-the [Kibosh](https://github.com/cf-platform-eng/kibosh) OSBAPI broker into a PCF Tile.
+the [Kibosh](https://github.com/cf-platform-eng/kibosh) OSBAPI broker, into a PCF Tile.
 
 When the tile is deployed, your Helm chart service will be available in the cf marketplace. 
-Developers can then `cf create-service` causing the chart to be helm installed on a 
+Developers can then `cf create-service` causing the chart to be Helm installed on a 
 Kubernetes cluster, and developer can `cf bind` the service to their application. 
 
 Use the following format in your tile.yml: 
@@ -538,24 +538,82 @@ By convention the name should match the name of the Helm chart found in Chart.ya
 helm_chart_dir is the path to the directory that contains Chart.yaml. 
 
 Prior to running `tile build`, there are some minor modifications that 
-may need be done to your helm chart. As described in the Configuration section of the 
+may need be done to your Helm chart. As described in the Configuration section of the 
 [Kibosh Readme](https://github.com/cf-platform-eng/kibosh/blob/master/README.md) you will need to: 
   - Create a plans.yaml file that defines the naming of your service in the cf marketplace. 
   - Create an images directory under helm_chart_dir. 
   - Download the Docker images used by your Helm chart from your repository 
-    (such as hub.docker.com) and put them into the images directory as .tgz files. 
-  - Reference each of those Docker images in your values.yaml file. 
+    (such as hub.docker.com) and put them into the images directory as .tgz files. You can name the 
+    files arbitrarily as long as they have a .tgz extension.  All .tgz Docker images in this directory
+    will be loaded by the tile into the private registry and the metadata inside the Docker image 
+    is the link to the image definitions in values.yaml. 
+  - Reference each of those Docker images in your values.yaml file.
+  - Modify any references to images in your Helm templates to point to the images using the 
+    required values.yaml structure. 
 These additions to the Helm chart allow the Kibosh broker and your tile to 
 manage and deploy your Helm chart in a consistent way across the PCF environment. 
 
-Here are some limitations to be aware of when deploying Helm charts into PKS Kubernetes clusters: 
+Example of building [Apache Spark Helm Chart](https://github.com/kubernetes/charts/tree/master/stable/spark) into a tile: 
+
+First, fetch the chart and the Docker images: 
+```
+$ git clone [email protected]:kubernetes/charts.git
+$ cd charts/stable/spark
+$ mkdir images && cd images
+$ docker pull k8s.gcr.io/spark:1.5.1_v3
+$ docker save k8s.gcr.io/spark:1.5.1_v3 -o spark-1.5.1_v3.tgz
+$ docker pull apache/zeppelin:0.7.3
+$ docker save apache/zeppelin:0.7.3 -o zeppelin-0.7.3.tgz
+```
+NOTE: in order to find the Docker images paths, look in [values.yml](https://github.com/kubernetes/charts/blob/master/stable/spark/values.yaml). 
+
+Next, modify values.yml and add: 
+```
+images:
+  spark:
+    image: "k8s.gcr.io/spark"
+    imageTag: "1.5.1_v3"
+  zeppelin:
+    image: "apache/zeppelin"
+    imageTag: "0.7.3"
+```
+
+Then, update your templates. Change references to `Image` and `ImageTag` (like this `{{ .Values.Master.Image }}`) to 
+the new image pattern (like `{{ .Values.images.spark.image }}`).   Note that Helm charts may use different
+patterns for specifying images.   The purpose of this step is to make those references consistent.
+
+Create the tile. 
+```
+# Create a directory outside the helm chart used above.  
+$ mkdir spark-tile && cd spark-tile
+$ tile init
+```
+Replace the contents of tile.yml with the following: 
+```
+---
+name: spark
+icon_file: icon.jpg
+label: Spark
+description: Spark k8s Tile
+
+packages:
+- name: spark
+  type: kibosh
+  helm_chart_dir: <path to spark helm chart created above>
+```
+Finally, generate the tile. (It is located at spark-tile/product/spark-<version>.pivotal)
+```
+$ tile build
+```
+
+Some limitations to be aware of when deploying Helm charts into PKS Kubernetes clusters: 
   - Once deployed, a persistent volume claim cannot be resized. This is the error that
     you may get if you try to resize: `Error: UPGRADE FAILED: 
     PersistentVolumeClaim is invalid: spec: Forbidden: field is immutable after creation`
   - Some disk types can be resized, but this requires enabling alpha
     [Feature Gates](https://kubernetes.io/docs/reference/feature-gates) 
   - [Selectors](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/#selector) 
-    are immutable. Many helm charts use name and other things as selectors, so cautions around changes. 
+    are immutable. Many Helm charts use name and other things as selectors, so cautions around changes. 
 
 
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