How to create a Single Node Cluster for OpenShift 4 on Power and Z

This post is written by Mick Tarsel, an IBM employee and Red Hat partner engineer working on OpenShift and Linux networking. 

The Single Node Cluster (SNC) project allows a user to easily spin up an OpenShift “cluster” on a single machine. SNC is used to build the bundles that CodeReady Containers (CRC) uses. Although you must have a valid user OpenShift pull secret, the SNC project is a simple way to set up your own OpenShift instance.

Please note the SNC and CRC projects are “as-is” on the Github repository. At this time, it is not a Red Hat supported solution.

A normal OpenShift 4 cluster (OCP4) is composed of many nodes that are typically represented as physical machines or Virtual Machines (VMs). Even a minimally sized cluster in OpenShift requires many hardware resources in order to experiment with, and this is something you would not be able to run on just your laptop! 

When an OCP4 cluster is created, several VMs are created with their respective roles. The two types of nodes in a OCP4 cluster I’ll further discuss are the master and worker nodes. As an example, a high availability cluster in OpenShift would require at least three masters and two worker nodes. Read more about required machines for a cluster.

NOTE: Although the vocabulary may not be appropriate at the time of this release, Red Hat and IBM are changing some terminology in their projects.

The master node manages other nodes in the cluster and schedules pods to run on those nodes, such as worker nodes. Since the worker node is managed by the master node, the worker hosts the pods and runs containerized applications. The worker contains the workload for your cluster. Each cluster has at least one worker node. SNC creates a single VM which is labeled as both the master and worker node: 

CRC uses this same design for development and testing; however, at this time, there are some limitations such as upgrading OpenShift versions. Using SNC or CRC you can have a master/worker instance in a single VM: 

SNC on Power and Z

The SNC project has been updated to enable both ppc64le and s390x. Since the 4.3 release of OpenShift, these architectures have been included in the official Red Hat mirror. This new multi-arch enablement in SNC is extremely beneficial for developers using Power and Z. Although these architectures are used in data centers around the world and are more than robust enough to handle a cluster, it is much easier and faster to create a single VM in order to run simple tests in OCP4.

To get started with OCP4 on your laptop, check out CRC. If you would like to build your own bundle and set up a single node cluster using Bash, try SNC. 

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