OpenShift - Deploy an application from a JSON or YAML file

An image contains the code used to create a deployment. Then, a deployment can be created from an image, which should then create a replica set (which is the number of pods that should be created), and then the pods should be created.

If you are not familiar with the oc command, refer to OpenShift - Getting Started with the oc command.

There are various ways to deploy an app.

A  JSON or YAML file that contains key value pairs can be used to create an object, such as a config map, deployment, a project, a pod, a route, a secret, a service, et cetera. These files are known as templates. For example, let's say you have a YAML file named deployment.yml that contains the following markup. Notice "kind: Deployment", which means this template will be used to create a deployment.

apiVersion: apps/v1
kind: Deployment
  name: hello-openshift
  replicas: 1
      app: hello-openshift
        app: hello-openshift
      - name: hello-openshift
        image: openshift/hello-openshift:latest
        - containerPort: 80


The oc apply or oc create command with the -f or --filename option can be used to create the deployment using the template JSON or YAML file.

The oc replace command can be used to replace a deployment using a new or updated template JSON or YAML file.

The oc edit command can be used to update a deployments template YAML file.

~]$ oc create --filename deployment.yml
deployment.apps/hello-openshift created


The oc get deployments command can be used to list the deployments. The DESIRED, CURRENT, UP-TO-DATE and AVAILABLE columns represent the number of replicas for the deployment.

Replicas is the number of pods that should be created for the deployment.

~]# oc get deployments --namespace <some namespace>
hello-openshift     1         1         1            1           23s


The oc get pods command can be used to determine if the pod is up and running.

~]$ oc get pods
NAME                READY   STATUS      RESTARTS   AGE
hello-openshift     1/1     Running     0          23s


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