Hello Everyone,
Hope you’re doing well. I’m going to write a series of articles on quick reference for Openshift. To check all other related articles please visit here. In this article we’ll deploy a simple application on Openshift cluster using oc new-app command.

Let’s understand oc new-app command with a example, run below command in your local and observe output :

#Passing Git Repo as a argument to new-app command
oc new-project myproject
oc new-app https://github.com/sclorg/cakephp-ex

The command will create below resources (run oc get all command),

NAME                     READY     STATUS      RESTARTS   AGE
pod/cakephp-ex-1-build   0/1       Completed   0          2m
pod/cakephp-ex-1-whxhr   1/1       Running     0          7s

NAME                                 DESIRED   CURRENT   READY     AGE
replicationcontroller/cakephp-ex-1   1         1         1         8s

NAME                 TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)             AGE
service/cakephp-ex   ClusterIP   172.30.1.243   <none>        8080/TCP,8443/TCP   2m

NAME                                            REVISION   DESIRED   CURRENT   TRIGGERED BY
deploymentconfig.apps.openshift.io/cakephp-ex   1          1         1         config,image(cakephp-ex:latest)

NAME                                        TYPE      FROM      LATEST
buildconfig.build.openshift.io/cakephp-ex   Source    Git       1

NAME                                    TYPE      FROM          STATUS     STARTED         DURATION
build.build.openshift.io/cakephp-ex-1   Source    Git@458ec0d   Complete   2 minutes ago   2m51s

NAME                                        DOCKER REPO                            TAGS      UPDATED
imagestream.image.openshift.io/cakephp-ex   172.30.1.1:5000/myproject/cakephp-ex   latest    9 seconds ago

#Passing Container Image location to new-app command
oc new-project mynewproject
oc new-app registry.hub.docker.com/sanketmodi/openshift-practice:hello-world

The command will create below resources (run oc get all command),

NAME                             READY     STATUS    RESTARTS   AGE
pod/openshift-practice-1-dkmqf   1/1       Running   0          10s

NAME                                         DESIRED   CURRENT   READY     AGE
replicationcontroller/openshift-practice-1   1         1         1         10s

NAME                                                    REVISION   DESIRED   CURRENT   TRIGGERED BY
deploymentconfig.apps.openshift.io/openshift-practice   1          1         1         config,image(openshift-practice:hello-world)

NAME                                                DOCKER REPO                                       TAGS          UPDATED
imagestream.image.openshift.io/openshift-practice   172.30.1.1:5000/mynewproject/openshift-practice   hello-world   11 seconds ago

Let’s understand what exactly happened in both the cases,

1. Passing git repo as argument :
When we passed git repo as argument, oc-new app command identified that there’s some code to be build. So it created a build configuration to build the project and generate image from the same. Once build was complete it created deployment configuration to get image and run the same.

2. Passing image as argument :
When we passed image as argument, oc new-app command identified that it’s a runnable image. So it directly created deployment configuration to download and run that image.

Build Configuration – Manages build process which creates container image.
Deployment Configuration – Manages deployment process (Running above created container.)
These two are primary resources which gets created based on the input type, there are few other auxiliary services like Image Stream, Services, Routes etc, few are created by default and others can be created when required. In above example, imagestream was created in both the cases, because openshift does tag management internally and doesn’t rely on outer source for the image.

That’s it for this article, I hope this article gave you a brief introduction on deploying application on openshift. Please let me know if you have any doubt / query in comment. For more articles on Openshift please visit quick reference page. Keep Learning, Keep Sharing and Stay Safe.