Before we get into the comparison, it's important to understand that Kubernetes and OpenShift are not two completely different tools. In fact, OpenShift builds on top of Kubernetes by extending its functionality and adding a more feature-rich developer experience. So, we can safely say that Kubernetes is an integral part of OpenShift, and there are many similarities between them. Both solutions enable users to dynamically deploy, scale, and operate their containerized workloads.
The main distinction is that Kubernetes is an open-source project that provides core functionality for managing containerized applications. On the other hand, OpenShift is a commercial product offered by Red Hat that provides a complete enterprise-level platform with added features, such as enhanced security, an integrated image registry, a built-in CI/CD pipeline component, and an out-of-the-box networking solution.
Because OpenShift is a commercial product, it features an enterprise support offering where you can reach out to a dedicated customer support team from Red Hat for any issues or assistance you require. Kubernetes doesn't provide this type of dedicated support, as it is a free and open-source tool; however, it has a vast community of developers that contribute to the project, and you can easily find solutions or answers to any issues on different platforms.
Let's now cover some technical differences between the two.
Integrated image registry
By default, Kubernetes doesn't have an internal image registry within the cluster. So, it relies on external registries, like Docker Hub, to pull images that it needs to run containers on the nodes. This requires extra network traffic to pull these images from outside the cluster each time a new image is used on one of the cluster nodes.
In contrast, OpenShift provides an integrated image registry within the cluster. It is one of the infrastructure components that can be installed and integrated perfectly with the cluster. It can use the cluster authentication and authorization system to provide access to images, and it can be used as a source for pulling images and as a target for publishing newly built images.
The internal image registry also supports multitenancy, where multiple namespaces, called "projects" in OpenShift terms, can have access to their respective images such that each project only sees its own images while being isolated from other images.
Builds and BuildConfigs
In addition to the internal image registry, OpenShift supports building images internally inside the cluster by using native OpenShift objects called builds and BuildConfigs. Builds transform an input from a specific source to an output OCI-compliant image. Sources can be a binary local directory containing a Dockerfile, a Git repository, or even another image.
A BuildConfig in OpenShift defines how to transform application source code into a container image. It defines when a new build should be triggered, which strategy to use to create the new image from the input, and where the output image is to be stored, which is typically inside the internal image registry. After an image is built and pushed using this native OpenShift build, we can use it directly from the image registry to deploy our applications.
By using builds and BuildConfigs, we don't need to build our images separately using a build server running a container engine or runtime. Thus, OpenShift enables managing the complete application lifecycle within the cluster. We can build, deploy, and run our applications all within the same OpenShift platform.
Kubernetes, however, doesn't have this native build functionality, which means an image build process needs to be managed separately using a container build tool. Once the image is built and pushed to some image registry, we can then use it to deploy our application on Kubernetes.
Container networking is an essential component of any container management platform. It controls things like network connectivity between containers, allocating and assigning IPs, creating subnets, configuring routes, and controlling network traffic flow.
Kubernetes doesn't come with a preinstalled networking solution. It provides a pluggable architecture in which users can install their preferred network plugin depending on what features they want the plugin to provide. Kubernetes enables this integration by using a standard interface called a "container networking interface," or CNI. CNIs define the specifications for creating and configuring container networking. Plugins for different network solutions then implement network functions by using and adhering to the CNI standards. So, users can install a CNI-compatible network plugin inside the Kubernetes cluster to provide the network functions they need.
On the other hand, OpenShift comes with an out-of-the-box networking solution. It uses a software-defined network (SDN) approach to create and manage container networking. This SDN solution is CNI compatible and enables the required communication between pods in the cluster. The OpenShift SDN creates an overlay networking model that uses Open vSwitch (OVS) as its underlying component.
Therefore, by using OpenShift, we don't have to install and configure a separate networking plugin in the cluster. We already have the option of using the SDN plugin that provides the functions we need for our network.
Command line and GUI-based configuration
When it comes to management, both Kubernetes and OpenShift provide different ways for developers and administrators to communicate with the cluster and apply their configuration.
Kubernetes provides a simple command line tool for users to interact with a cluster called kubectl. Kubectl is a lightweight client that can be installed on Linux, Windows, or macOS. Users can run commands against the cluster, and kubectl takes these commands and translates them into API calls that correspond to the requested instruction. We can use kubectl to deploy applications, view logs, monitor the health of objects, or carry out other administrative tasks on the cluster.
OpenShift has a similar command line interface tool called oc. The oc tool can be installed on different client operating systems using the operating system's package manager, or we can download and install its binary manually. We can use the oc commands to configure and manage the OpenShift cluster in the same way we use kubectl for Kubernetes.
OpenShift also provides an additional GUI web interface that comes along with the cluster, with no additional installations required. We can deploy and manage our applications, create cluster objects, and apply the configuration we need using this web console in the same way as we do using the command line.
Kubernetes, however, doesn't provide a default GUI option for managing the cluster. We can install additional dashboards or a GUI interface on the cluster, but it doesn't come as a default component with Kubernetes.
One of the biggest differences between OpenShift and Kubernetes is how they handle cluster security. It's a clear, one-sided advantage for OpenShift over native Kubernetes.
OpenShift provides stricter security measures that come with its default setup. It has default support for role-based access control (RBAC) to enable least privilege access, where users only have permissions to apply the configurations they're allowed to do. An authentication and authorization system is provided by default on an OpenShift cluster, and users must be granted access through it. OpenShift also restricts permissions for containers running on the platform. For example, it prevents the execution of containers as root by default and limits their access to system resources.
Although Kubernetes can support some of these features, they're are not presented by default, and it can be complicated to set them up accurately.
The continuous integration and continuous delivery method has become a standard process in today's modern software industry. It improves software quality, minimizes delivery times, and enables faster feedback loops for code changes introduced to the application. This process is usually implemented using an automation system that orchestrates different stages of the software lifecycle. This ensures a consistent, repeatable, and reliable way for software delivery.
OpenShift provides a default feature for implementing CI/CD called OpenShift pipelines. It is a cloud-native, serverless system that enables automated deployment on different platforms. It works by defining some Kubernetes custom resource definitions (CRD) that we can use as building blocks to create our pipelines. By using standard Kubernetes CRDs, these pipelines can be moved between different Kubernetes distributions, which makes them portable and reusable.
OpenShift also allows integration with other external CI/CD systems like Jenkins. This gives users the choice to run their preferred CI/CD solution and combine it with OpenShift builds and deployments.
In contrast, Kubernetes doesn't have a built-in CI/CD system like OpenShift, but it supports integrating external systems to create pipelines that automate deployments on the Kubernetes clusters.
Given that OpenShift is built on top of Kubernetes, you might wonder if learning Kubernetes is a mandatory prerequisite for getting started with OpenShift. The answer is, we don't have to be Kubernetes experts, but we'll need to understand the core Kubernetes concepts as they're at the heart of OpenShift. After gaining a basic understanding of Kubernetes, transitioning to OpenShift may be beneficial, as it provides additional abstractions and tools to simplify operations and application management.
However, even if you are well versed in Kubernetes, you may find learning OpenShift to be a logical extension of your existing knowledge. OpenShift is often referred to as "Enterprise Kubernetes" by Red Hat, which is justified in my view. As a Kubernetes expert, you have to be acquainted with these technologies:
OpenShift architecture: OpenShift is a complex platform with a number of different components, including the Kubernetes cluster itself, the OpenShift Console, and the OpenShift API.
OpenShift features: OpenShift adds a number of features to Kubernetes, such as built-in CI/CD pipelines, image registry, ImageStreams, routes, DeploymentConfigs, builds, and BuildConfigs.
OpenShift commands: OpenShift is primarily managed through the command line.
OpenShift vs. Kubernetes: Which one to choose?
Choosing the right container orchestration platform for your organization can be a daunting task that requires in-depth knowledge of your organization's processes and a fundamental understanding of the features and requirements of different solutions.
Generally speaking, we can say that if your organization needs an enterprise-level platform that offers a complete set of out-of-the-box features with minimal initial setup and configuration along with commercial product support, you'll need to go for OpenShift.
Also, if your organization prioritizes security or has strict regulatory and compliance requirements to meet specific standards like financial or health services, OpenShift will also be the perfect choice by far as it implements a strong security model that is offered by default.
OpenShift provides a more developer-centric platform with features like CI/CD pipelines, source-to-image builds, and integrated developer tools that can significantly streamline the development workflow.
On the other hand, if you need a customizable platform that offers more flexibility that you can tailor to your organization-specific needs, and you have an experienced team of Kubernetes experts who can easily set up and configure different parts of the solution, then Kubernetes will be a better choice.
Kubernetes, being a cornerstone of cloud-native technologies, might be preferred by organizations looking to adopt a cloud-native approach, especially those looking to stay close to the Cloud Native Computing Foundation (CNCF) ecosystem.
Although it's open source, deploying Kubernetes in a public cloud can result in significant costs for your organization. The major public cloud providers, such as Amazon Web Services (AWS), Microsoft Azure, Google Cloud Platform (GCP), and IBM Cloud, offer OpenShift services just like Kubernetes. These providers offer different editions of Red Hat OpenShift that cater to both fully managed and self-managed configurations based on your organizational requirements. OpenShift is often seen as the more expensive option due to its enterprise-grade features, support, and management services.
In summary, OpenShift might be a better fit for larger enterprise-level organizations or those in regulated industries, while Kubernetes might be more appealing to tech-savvy organizations, startups, or those with existing Kubernetes expertise.
OpenShift is an enterprise commercial product that offers dedicated support with a subscription-based model. Kubernetes is an open-source project offered for free use and has a large community of contributors who offer help and assistance.
OpenShift provides a more feature-rich platform with built-in features, such as an integrated image registry, out-of-the box networking solution, strict security controls, and native CI/CD support.
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Kubernetes doesn't come with the same built-in options as OpenShift; however, it supports external integrations with a large ecosystem of software solutions that can provide the same functionality but with additional management and setup overhead and complexity.