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OpenShift Container Platform is a cloud-based Kubernetes container platform. The foundation of OpenShift Container Platform is based on Kubernetes and therefore shares the same technology. It is designed to allow applications and the data centers that support them to expand from just a few machines and applications to thousands of machines that serve millions of clients.

OpenShift Container Platform enables you to do the following:

  • Provide developers and IT organizations with cloud application platforms that can be used for deploying applications on secure and scalable resources.

  • Require minimal configuration and management overhead.

  • Bring the Kubernetes platform to customer data centers and cloud.

  • Meet security, privacy, compliance, and governance requirements.

With its foundation in Kubernetes, OpenShift Container Platform incorporates the same technology that serves as the engine for massive telecommunications, streaming video, gaming, banking, and other applications. Its implementation in open Red Hat technologies lets you extend your containerized applications beyond a single cloud to on-premise and multi-cloud environments.

Glossary of common terms for OpenShift Container Platform

This glossary defines common Kubernetes and OpenShift Container Platform terms. These terms help you orient yourself with the content and other parts of the documentation.

Kubernetes

Kubernetes is an open source container orchestration engine for automating deployment, scaling, and management of containerized applications.

Containers

Containers are application instances and components that run in OCI-compliant containers on the worker nodes. A container is the runtime of an Open Container Initiative (OCI)-compliant image. An image is a binary application. A worker node can run many containers. A node capacity is related to memory and CPU capabilities of the underlying resources whether they are cloud, hardware, or virtualized.

Pod

A pod is one or more containers deployed together on one host. It consists of a colocated group of containers with shared resources such as volumes and IP addresses. A pod is also the smallest compute unit defined, deployed, and managed.

In OpenShift Container Platform, pods replace individual application containers as the smallest deployable unit.

Pods are the orchestrated unit in OpenShift Container Platform. OpenShift Container Platform schedules and runs all containers in a pod on the same node. Complex applications are made up of many pods, each with their own containers. They interact externally and also with another inside the OpenShift Container Platform environment.

Replica set and replication controller

The Kubernetes replica set and the OpenShift Container Platform replication controller are both available. The job of this component is to ensure the specified number of pod replicas are running at all times. If pods exit or are deleted, the replica set or replication controller starts more. If more pods are running than needed, the replica set deletes as many as necessary to match the specified number of replicas.

Deployment and DeploymentConfig

OpenShift Container Platform implements both Kubernetes Deployment objects and OpenShift Container Platform DeploymentConfigs objects. Users may select either.

Deployment objects control how an application is rolled out as pods. They identify the name of the container image to be taken from the registry and deployed as a pod on a node. They set the number of replicas of the pod to deploy, creating a replica set to manage the process. The labels indicated instruct the scheduler onto which nodes to deploy the pod. The set of labels is included in the pod definition that the replica set instantiates.

Deployment objects are able to update the pods deployed onto the worker nodes based on the version of the Deployment objects and the various rollout strategies for managing acceptable application availability. OpenShift Container Platform DeploymentConfig objects add the additional features of change triggers, which are able to automatically create new versions of the Deployment objects as new versions of the container image are available, or other changes.

Service

A service defines a logical set of pods and access policies. It provides permanent internal IP addresses and hostnames for other applications to use as pods are created and destroyed.

Service layers connect application components together. For example, a front-end web service connects to a database instance by communicating with its service. Services allow for simple internal load balancing across application components. OpenShift Container Platform automatically injects service information into running containers for ease of discovery.

Route

A route is a way to expose a service by giving it an externally reachable hostname, such as www.example.com. Each route consists of a route name, a service selector, and optionally a security configuration. A router can consume a defined route and the endpoints identified by its service to provide a name that lets external clients reach your applications. While it is easy to deploy a complete multi-tier application, traffic from anywhere outside the OpenShift Container Platform environment cannot reach the application without the routing layer.

Build

A build is the process of transforming input parameters into a resulting object. Most often, the process is used to transform input parameters or source code into a runnable image. A BuildConfig object is the definition of the entire build process. OpenShift Container Platform leverages Kubernetes by creating containers from build images and pushing them to the integrated registry.

Project

OpenShift Container Platform uses projects to allow groups of users or developers to work together, serving as the unit of isolation and collaboration. It defines the scope of resources, allows project administrators and collaborators to manage resources, and restricts and tracks the user’s resources with quotas and limits.

A project is a Kubernetes namespace with additional annotations. It is the central vehicle for managing access to resources for regular users. A project lets a community of users organize and manage their content in isolation from other communities. Users must receive access to projects from administrators. But cluster administrators can allow developers to create their own projects, in which case users automatically have access to their own projects.

Each project has its own set of objects, policies, constraints, and service accounts.

Projects are also known as namespaces.

Operators

An Operator is a Kubernetes-native application. The goal of an Operator is to put operational knowledge into software. Previously this knowledge only resided in the minds of administrators, various combinations or shell scripts or automation software such as Ansible. It was outside your Kubernetes cluster and hard to integrate. With Operators, all of this changes.

Operators are purpose-built for your applications. They implement and automate common Day 1 activities such as installation and configuration as well as Day 2 activities such as scaling up and down, reconfiguration, updates, backups, fail overs, and restores in a piece of software running inside your Kubernetes cluster by integrating natively with Kubernetes concepts and APIs. This is called a Kubernetes-native application.

With Operators, applications must not be treated as a collection of primitives, such as pods, deployments, services, or config maps. Instead, Operators should be treated as a single object that exposes the options that make sense for the application.

Understanding OpenShift Container Platform

OpenShift Container Platform is a Kubernetes environment for managing the lifecycle of container-based applications and their dependencies on various computing platforms, such as bare metal, virtualized, on-premise, and in cloud. OpenShift Container Platform deploys, configures and manages containers. OpenShift Container Platform offers usability, stability, and customization of its components.

OpenShift Container Platform utilises a number of computing resources, known as nodes. A node has a lightweight, secure operating system based on Red Hat Enterprise Linux (RHEL), known as Red Hat Enterprise Linux CoreOS (RHCOS).

After a node is booted and configured, it obtains a container runtime, such as CRI-O or Docker, for managing and running the images of container workloads scheduled to it. The Kubernetes agent, or kubelet schedules container workloads on the node. The kubelet is responsible for registering the node with the cluster and receiving the details of container workloads.

OpenShift Container Platform configures and manages the networking, load balancing and routing of the cluster. OpenShift Container Platform adds cluster services for monitoring the cluster health and performance, logging, and for managing upgrades.

The container image registry and OperatorHub provide Red Hat certified products and community built softwares for providing various application services within the cluster. These applications and services manage the applications deployed in the cluster, databases, frontends and user interfaces, application runtimes and business automation, and developer services for development and testing of container applications.

You can manage applications within the cluster either manually by configuring deployments of containers running from pre-built images or through resources known as Operators. You can build custom images from pre-build images and source code, and store these custom images locally in an internal, private or public registry.

The Multicluster Management layer can manage multiple clusters including their deployment, configuration, compliance and distribution of workloads in a single console.