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Exercise 4 - ConfigMaps

We want to change the index.html served by the Apache HTTP Server in order to personalize our website. There are multiple approaches to achieve this:

  • change the container image by adding the file during the build to the image (out of scope for this workshop)
  • use a ConfigMap to inject the file to the container in the Pod

ConfigMap provides a mechanisms to inject containers with configuration data (entire files or single values) while keeping the containers unchanged.

Check out the OpenShift or Kubernetes Documentation for more information about ConfigMaps.

Note

For each exercise you can choose and only have to do either the 'Web Console' or the 'Command Line Interface (CLI)' section in oder to complete the exercise.

Create a ConfigMap

  1. Switch to the 'Administrator' view using the dropdown menu at .
  2. Navigate to 'Workloads' → 'Config Maps' .
  3. Switch to the your project using the dropdown menu at . In each of the exercise make sure that you are in your project context before you are making any changes.
  4. Press 'Create Config Map' .

  5. Create a ConfigMap with the index.html using the content below: 

    <!DOCTYPE html>
<html>
<head>
    <title>John Doe</title>
</head>
<body>
    <h1>John Doe</h1>
    <p>
    Today I learned how to deploy my own website in the cloud
    using an Apache HTTP Server (httpd) running on OpenShift.
    </p>
</body>
</html>
    (replace John Doe with your actual name - if you are John Doe you can skip this)

    Try to create the ConfigMap definition file on your own using the template at and the additional schema information

    Solution: 

    apiVersion: v1
kind: ConfigMap
metadata:
  name: httpd
data:
  index.html: |-
    <!DOCTYPE html>
    <html>
    <head>
        <title>John Doe</title>
    </head>
    <body>
        <h1>John Doe</h1>
        <p>
        Today I learned how to deploy my own website in the cloud
        using an Apache HTTP Server (httpd) running on OpenShift.
        </p>
    </body>
    </html>

  6. Press 'Create' .

Mount a ConfigMap

  1. Navigate to 'Workloads' → 'Deployments' .
  2. Open the 'Deployment Details' by clicking on the 'Name' .
  3. Switch to the 'YAML' tab .
  4. Add the highlighted parts to the Deployment defintion file in the editor : 
    apiVersion: apps/v1
kind: Deployment
...
spec:
  ...
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: httpd
    spec:
      volumes:
      - name: html
        configMap:
          name: <configmap name> 
      containers:
      - image: ubi9/httpd-24:latest
        volumeMounts:
        - name: html
          mountPath: /var/www/html
        ...
  5. Press 'Save' .
  6. Reload your web site using the URL of the Route created in Exercise 3.

Important

At the beginning of the exercise make sure that you are in your project context. 

oc project <project name>

Create a ConfigMap

  1. Create a index.html file using the vi editor with the following content: 
    <!DOCTYPE html>
<html>
<head>
    <title>John Doe</title>
</head>
<body>
    <h1>John Doe</h1>
    <p>
    Today I learned how to deploy my own website in the cloud
    using an Apache HTTP Server (httpd) running on OpenShift.
    </p>
</body>
</html>
    (replace John Doe with your actual name - if you are John Doe you can skip this)

  2. Create a ConfigMap with the index.html.

    Try to figure out how to create a new configmap named httpd based on a file using oc create configmap -h

    Solution: 

    oc create configmap httpd --from-file=index.html

Inspect a ConfigMap

  1. Inspect the created ConfigMap using oc get and oc describe. 
    oc get configmaps

    oc describe configmap <configmap name>
  2. Also check the ConfigMap in the Web Console.

Mount a ConfigMap

  1. Let's add the ConfigMap to the Pod template in the Deployment. The oc edit command allows us to edit existing resources using the vi editor. 
    oc edit deployment <deployment name>
  2. Add the highlighted parts to the Deployment: 
    apiVersion: apps/v1
kind: Deployment
...
spec:
  ...
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: httpd
    spec:
      volumes:
      - name: html
        configMap:
          name: <configmap name> 
      containers:
      - image: ubi9/httpd-24:latest
        volumeMounts:
        - name: html
          mountPath: /var/www/html
        ...
  3. Store and close the file. The configuration change triggers automatically a redeployment of all your Pods - wait a couple of seconds until it is done.
  4. Reload your web site using the URL of the Route created in Exercise 3.

🎉 Congratulations, you have made it!

You have successfully deployed your first personal website in the cloud using OpenShift. 👏