Overview

You can populate your OKD installation with useful sets of Red Hat-provided image streams and templates to make it easy for developers to create new applications. By default, the By default, the cluster installation process automatically creates these sets in the openshift project, which is a default project to which all users have view access.

Image streams and templates are provided for the following technologies:

Type Technology

Languages & Frameworks

Databases

Other Services

Before You Begin

Before you consider performing the tasks in this topic, confirm if these image streams and templates are already registered in your OKD cluster by doing one of the following:

  • Log into the web console and click Add to Project.

  • List them for the openshift project using the CLI:

    $ oc get is -n openshift
    $ oc get templates -n openshift

If you used a method other than the standard cluster installation process, or if the default image streams and templates are ever removed or changed, you can follow this topic to create the default objects yourself. Otherwise, the following instructions are not necessary.

Prerequisites

Before you can create the default image streams and templates:

  • The integrated Docker registry service must be deployed in your OKD installation.

  • You must be able to run the oc create command with cluster-admin privileges, because they operate on the default openshift project.

  • You must have cloned the repository that contains the default image streams and templates:

    $ cd ~
    $ git clone https://github.com/openshift/openshift-ansible
  • Define shell variables for the directories containing image streams and templates. This significantly shortens the commands in the following sections. To do this:

    $ IMAGESTREAMDIR=~/openshift-ansible/roles/openshift_examples/files/examples/v3.10/image-streams; \
        DBTEMPLATES=~/openshift-ansible/roles/openshift_examples/files/examples/v3.10/db-templates; \
        QSTEMPLATES=~/openshift-ansible/roles/openshift_examples/files/examples/v3.10/quickstart-templates

Creating Image Streams for OKD Images

If your node hosts are subscribed using Red Hat Subscription Manager and you want to use the core set of image streams that used Red Hat Enterprise Linux (RHEL) 7 based images:

$ oc create -f $IMAGESTREAMDIR/image-streams-rhel7.json -n openshift

Alternatively, to create the core set of image streams that use the CentOS 7 based images:

$ oc create -f $IMAGESTREAMDIR/image-streams-centos7.json -n openshift

Creating both the CentOS and RHEL sets of image streams is not possible, because they use the same names. To have both sets of image streams available to users, either create one set in a different project, or edit one of the files and modify the image stream names to make them unique.

Creating Database Service Templates

The database service templates make it easy to run a database image which can be utilized by other components. For each database (MongoDB, MySQL, and PostgreSQL), two templates are defined.

One template uses ephemeral storage in the container which means data stored will be lost if the container is restarted, for example if the pod moves. This template should be used for demonstration purposes only.

The other template defines a persistent volume for storage, however it requires your OKD installation to have persistent volumes configured.

To create the core set of database templates:

$ oc create -f $DBTEMPLATES -n openshift

After creating the templates, users are able to easily instantiate the various templates, giving them quick access to a database deployment.

Creating Instant App and Quickstart Templates

The Instant App and Quickstart templates define a full set of objects for a running application. These include:

Some of the templates also define a database deployment and service so the application can perform database operations.

The templates which define a database use ephemeral storage for the database content. These templates should be used for demonstration purposes only as all database data will be lost if the database pod restarts for any reason.

Using these templates, users are able to easily instantiate full applications using the various language images provided with OKD. They can also customize the template parameters during instantiation so that it builds source from their own repository rather than the sample repository, so this provides a simple starting point for building new applications.

To create the core Instant App and Quickstart templates:

$ oc create -f $QSTEMPLATES -n openshift

What’s Next?

With these artifacts created, developers can now log into the web console and follow the flow for creating from a template. Any of the database or application templates can be selected to create a running database service or application in the current project. Note that some of the application templates define their own database services as well.

The example applications are all built out of GitHub repositories which are referenced in the templates by default, as seen in the SOURCE_REPOSITORY_URL parameter value. Those repositories can be forked, and the fork can be provided as the SOURCE_REPOSITORY_URL parameter value when creating from the templates. This allows developers to experiment with creating their own applications.

You can direct your developers to the Using the Instant App and Quickstart Templates section in the Developer Guide for these instructions.