OpenShift for Developers, 2nd Edition

Chapter 2. OpenShift Concepts

OpenShift is a superset of Kubernetes. Kubernetes concepts, commands, and practices work on OpenShift. You can do any of the usual kubectl operations in the OpenShift API. The reverse is not true. OpenShift has features and entire workflows that are not part of Kubernetes. For example, BuildConfig and Build resources in the OpenShift API represent the configuration and iterative executions of a process to build an application. They are not in the Kubernetes API, because Kubernetes doesn’t define a mechanism for compiling software and assembling container images. OpenShift adds these two types of resources and the facilities that use them. Likewise, while Kubernetes has a namespace to organize resources, OpenShift augments the namespace to form the Project. A Project demarcates access boundaries for clusters occupied by multiple tenants and serves as a discrete unit for administrative policy.

Kubernetes establishes the components of a container orchestrator and a way of addressing them. OpenShift builds on that foundation, adding tools and abstractions for the developers who build the apps that run on the cluster. Keeping those apps running is the reason the cluster exists.

This chapter introduces key concepts for building, deploying, and maintaining applications with OpenShift. It notes where these concepts extend or replace Kubernetes abstractions. We’ll begin by explaining how OpenShift Projects extend the basic Kubernetes namespace.

Projects Organize ...