Create an App from a Docker image

In this recipe you will learn how to create a new project on OpenShift and how to create an application from an existing docker image.

Add a new project from command line

$ oc new-project ocp-test --display-name="OCP Test" --description="This is OCP Test"

Upon project creation, OpenShift will automatically switch to the newly created project/namespace. If you wish to view the list of projects, run the following command:

$ oc get projects

If you have more than one project, you can switch to a different one by issuing oc project <project name>. Although you don’t want to do it now.

You can also check the status of the project by running the following command. It says that the project is currently not running anything.

$ oc status
In project OCP Test (ocp-test) on server

You have no services, deployment configs, or build configs.
Run 'oc new-app' to create an application.

Create an application from a Docker Image

Next we will create an application inside the above project using an existing docker image. We will be using a very simple docker image on dockerhub that just says "Welcome to OpenShift V3". Let us just use that for this exercise.

First create a new application using the docker image using the oc new-app command as shown below:

$ oc new-app redhatworkshops/welcome-php --name=welcome
--> Found Docker image 3e73433 (7 months old) from Docker Hub for "redhatworkshops/welcome-php"

    Platform for building and running PHP 5.6 applications

    Tags: builder, php, php56, rh-php56

    * An image stream will be created as "welcome:latest" that will track this image
    * This image will be deployed in deployment config "welcome"
    * Port 8080/tcp will be load balanced by service "welcome"
      * Other containers can access this service through the hostname "welcome"

--> Creating resources ...
    imagestream "welcome" created
    deploymentconfig "welcome" created
    service "welcome" created
--> Success
    Run 'oc status' to view your app.

The above command uses the docker image to deploy a docker container in a pod. If you quickly run oc get pods you will notice that a deployer pod runs and it starts an application pod as shown below.

$ oc get pods
NAME              READY     STATUS    RESTARTS   AGE
welcome-1-xw3dn   1/1       Running   0          2m

Add a Route for your application

OpenShift also spins up a service for this application. Run the following command to view the list of services in the project.

$ oc get services
welcome   <none>        8080/TCP   4m

You will notice the welcome service was created for this project.

However, there is no route for this application yet. So you cannot access this application from outside.

Now add a route to the service with the following command. oc expose command will allow you to expose your service to the world so that you can access it from the browser.

$ oc get service
welcome   <none>        8080/TCP   8m

Try your application

To get the test HOST/PORT via

$ oc get route
NAME      HOST/PORT                                         PATH      SERVICES   PORT       TERMINATION   WILDCARD
welcome             welcome    8080-tcp                 None

Access the application: Now access the application using curl (looking for 200 status code) or from the browser and see the result

$ curl -Is
HTTP/1.1 200 OK
Date: Sun, 09 Jul 2017 12:55:32 GMT
Server: Apache/2.4.18 (Red Hat)
Content-Type: text/html; charset=UTF-8
Set-Cookie: 29bd1045b4b73d6a6c47bc9bded48f0e=4edfbf67d301fe8a2fdc3e8885379a15; path=/; HttpOnly
Cache-control: private

Voila!! you created your first application using an existing docker image on OpenShift.

Clean up

Run the oc get all command to view all the components that were created in your project.

$ oc get all
NAME         DOCKER REPO                            TAGS      UPDATED
is/welcome   latest    12 minutes ago

dc/welcome   1          1         1         config,image(welcome:latest)

rc/welcome-1   1         1         1         12m

NAME             HOST/PORT                                         PATH      SERVICES   PORT       TERMINATION   WILDCARD
routes/welcome             welcome    8080-tcp                 None

svc/welcome   <none>        8080/TCP   12m

NAME                 READY     STATUS    RESTARTS   AGE
po/welcome-1-xw3dn   1/1       Running   0          12m

Now you can delete all these components by running one command.

$ oc delete all --all
imagestream "welcome" deleted
deploymentconfig "welcome" deleted
route "welcome" deleted
service "welcome" deleted

You will notice that it has deleted the imagestream for the application, the deploymentconfig, the service and the route.

You can run oc get all again to make sure the project is empty.

Congratulations!! You now know how to create a project, an application using an external docker image and navigate around. Get ready for more fun stuff!

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