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Kubernetes Vs. Docker Vs. OpenShift: What's The Difference?

In this guide, we cover the differences between Kubernetes, Docker, and Openshift — and which platform you should use as your containerization system.

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Your organization may be among the 68% that is increasing container adoption. Or you might be among the 32% that are yet to decide. Either way, containers are a big deal today. The 2021 Kubernetes Adoption Survey revealed a majority of organizations will implement the technology for their biggest tech challenges today. 

The respondents said they hoped to reduce engineering costs, speed deployments, develop and test artificial intelligence (AI) models, as well as automate more. 

It's likely that you want those benefits, too. So you may be curious about the best containerization ecosystem to get started. Among the top contenders, Docker, OpenShift, and Kubernetes are all excellent options. 

It is worth considering how Kubernetes, Docker, and OpenShift differ, beginning with their definitions and primary functions. In this in-depth guide, we’ll cover each platform as well as the benefits and disadvantages of each, and whether Kubernetes, Docker, or OpernShift are right for you.

Table Of Contents

Kubernetes Vs. Docker Vs. OpenShift: Overview

Despite 90% of organizations using containers in production, there’s often confusion around Kubernetes, Docker, and OpenShift. For instance, some people refer to Kubernetes as an all-in-one containerization platform. But that isn’t accurate as you’ll find out later on in this article.  

It's also possible that you are reading this after learning Kubernetes no longer supports Docker in kubelets. So perhaps you are wondering which platform to use moving forward. 

OpenShift also markets itself as a Platform-as-a-Service (PaaS). Yet, OpenShift comprises Kubernetes components and works with Docker. Is OpenShift still reliant on Docker and Kubernetes? 

In this post, we will cover each of these vital containerization technologies. Then, we'll discuss the critical differences between them so you can see why you might need each.  

What Is Kubernetes?

Kubernetes is an open-source container orchestration platform. Engineers use it to automate deploying and managing clustered groups of hosts that run Linux containers. Kubernetes (K8s) work on most clouds, including on-premise, public cloud, and hybrid clouds.

Kubernetes is often called a Container-as-a-Service because it lets engineers manage and monitor services and workloads. 

Google designed, developed, and used Kubernetes for almost a decade as BORG before donating it to the Cloud Native Computing Foundation in 2015. Red Hat, AWS, Microsoft, Google Cloud, and IBM are among the cloud providers contributing to its improvement. 

A few key features of Kubernetes include: 

  • Containers that auto-scale, including horizontal scaling (outwards and inwards).
  • Manages the storage containers need (storage orchestration).
  • Detect, restart, or replace containers that fail automatic health checks through self-monitoring, recovery, and healing.
  • Manages Continuous Integration (CI) workloads.
  • Run containers across multi-clouds (hybrid cloud strategy)
  • Distributes load between containers for optimal resource use and smooth operation (load balancing).
  • Provides a powerful method for rolling out application updates 

As an engineer, you can use Kubernetes as a platform, as a type of container operating system, and as a container orchestration tool. However, Kubernetes is not an all-in-one solution for containers since it requires various plugins and tools to work.   

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What Is Docker?

Docker is open-source container technology, platform, and tool for cloud and on-premises use. 

Docker Engine is a runtime environment that helps build containers for an application using Docker files and Docker images. Engineers also use Docker Engine for running containers. Docker Swarm (Swarm or swarm mode) is also the native container orchestration tool that engineers can use to manage Docker engines. 

Additionally, engineers who do not want to create Docker images from scratch can use Docker Hub to store and share images. 

Docker Swarm is the Kubernetes alternative and container scheduler that people think of when comparing Kubernetes vs Docker. They are both orchestrators. Both strive to get their respective ecosystems to the desired state and actively fix container issues that deviate from that state. 

Docker launched in 2003, over a decade before Kubernetes became generally available as an open-source project under the CNCF. So Docker is a mature platform. 

What is the relationship between Docker and Kubernetes now?  

Docker engineers had trouble managing containers, especially in large-scale production environments. This led Google engineers to develop Kubernetes. 

Kubernetes became widely popular for orchestrating Docker containers across up to 5,000 nodes. Docker also became an equally popular container runtime layer for Kubernetes. 

Yet, in Kubernetes 1.20, you do not need Docker since several container runtime options are available now. In addition, Docker does not yet support Container Runtime Interface (CRI), the way Kubernetes communicates with a container runtime. So Kubernetes will no longer provide special support for Docker as it has done in the past. 

Still, Kubernetes may have had a hard time working with Docker because of the three layers it had to support. 

Furthermore, Docker is built upon a third-party container runtime platform called containerd, which gives Docker its runtime privileges. It has been difficult for Kubernetes to use containerd directly until recently.

Still, you can:

  • Use Docker files and Docker images (OCI format) to build container images for Kubernetes.  
  • Store and share your Docker images in Docker Hub because Kubernetes still pulls from Docker registries like Azure Container Registry and Docker Hub. 

You just won’t be able to use Docker as a container runtime under Kubernetes anymore.

Can you use Docker without Kubernetes?

Docker engineers do not need Kubernetes. Docker can build and manage container images in a registry. Similarly, it can run, communicate, and use Docker Compose to bundle containers into a multi-container app.

Some engineers prefer that setup because Kubernetes can be notoriously complex, thus challenging to manage at scale.

Docker also offers Docker Swarm (swarm mode), the native tool for cluster management and scheduling. However, engineers can now choose whether they want to use Swarm or Kubernetes to manage clusters.  

Unlike Kubernetes, which is better suited to growing startups and enterprises, Docker Swarm is better suited to small businesses.   

What Is OpenShift?

OpenShift is an open-source container technology developed by Red Hat to help large-scale organizations develop, deploy, and orchestrate containers. It consists of a suite of five container orchestration tools, which include: 

  • Red Hat OpenShift Container Platform
  • Red Hat OpenShift Dedicated (public cloud)
  • Microsoft Azure Red Hat OpenShift
  • Amazon Red Hat OpenShift
  • Red Hat OpenShift on IBM Cloud

Red Hat built OpenShift on top of its OKD (OpenShift Origin), Kubernetes, and Docker technologies. Using Docker, engineers could build Docker container images using an integrated development environment (IDE) and Kubernetes for container cluster management.

We say “used” because OpenShift also moved from Docker to Podium with its OpenShift 4.X and Red Hat Enterprise Linux (RHEL) 8.0 updates. 

OpenShift is a Kubernetes distribution because it combines Kubernetes components with Red Hat features. To be fair, Red Hat and Google were early, heavy contributors to Kubernetes.   

OpenShift Diagram

Credit: Levvel

As with Kubernetes and Docker, OpenShift is a platform (PaaS) and a tool (CaaS). It also supports automatic and manual scaling of containers, CI/CD tools, and multi-tenant deployments. 

However, it also offers premium support, security features right out of the box, a login portal, and support for multiple languages (Go, Node.js, Java, Ruby, Python, and PHP). 

Docker Vs. Kubernetes Vs. OpenShift: What Are The Differences?

1. Projects vs. product

Red Hat's OpenShift Container Platform (4.X is the latest version) is a subscription-based commercial software product. Red Hat engineers develop, maintain, and upgrade it. You can check out OKD (OpenShift Origin) to explore OpenShift's open-source project side.

Docker has two versions; Docker Community Edition (CE), a free version, and Docker Enterprise Edition (EE), the paid solution with enterprise-level support. 

Kubernetes is an open-source project you can use for free — so long as you invest in its infrastructure.   

2. Deployment, installation, and running environments

Installing OpenShift commercially requires Red Hat Enterprise Linux or Atomic (for OpenShift 3.0) and Red Hat CoreOS (for OpenShift 4). For the free version of OKD, you would need RHEL or CentOS. 

There are a number of public and private cloud providers that support it, too. They include Amazon, Microsoft Azure, and IBM Cloud. 

Kubernetes and Docker work with any Linux distribution. Ubuntu, Fedora, and Debian are examples of such distributions. CentOS supports Docker as well.

You can deploy both to public, private, on-premises, and hybrid environments. Both also work with Mac and Windows desktop computers. Besides Windows 10, Docker is compatible with Windows Server 1709 and 2016. 

What's more is if you need help managing Kubernetes, Google Cloud (GKE), Microsoft Azure (AKS), and AWS (Amazon EKS) offer managed services.  

3. Container image management 

A favorite image management tool for many engineers is ImageStream in OpenShift. Kubernetes, on the other hand, still does not include a container image management system. For instance, no integrated image registry is available. It will allow you to create a Docker image registry instead, such as Docker Hub. Kubernetes then pulls images from there. 

Docker provides the Docker Hub registry, and you can store and share images with compatible registries such as Azure Container Registry. Docker Pro or Team members also have access to the new Advanced Image Management Dashboard.  

4. Scalability and size

All three solutions support both automatic and manual scaling. However, Kubernetes' inherent extensibility and horizontal scaling capabilities make it the most scalable compared to Docker's auto-scaling groups. 

Kubernetes is also the largest of the three. 

Compare it with Docker, for example. Kubernetes can support up to 5,000 nodes compared to Docker Swarm's 1,000 nodes and 30,000 containers (30 containers per node) instead of 300,000 containers on Kubernetes. 

5. Security

OpenShift's commercial editions come with tighter security features out of the box. OpenShift won’t let users run a container as a root, for instance. You also can’t run many official images or simple container images. Also, your OpenShift environment must maintain a minimum security level. 

Its integrated server also simplifies the authorization and authentication processes for users.

OpenShift scans images for vulnerabilities, which is something Docker also does. 

OpenShift Security

The Docker Swarm nodes also implement TLS mutual encryption and authentication to protect what they communicate with each other.  

Although all three platforms support role-based access control (RBAC), OpenShift further provides stricter policies with security context constraints (SCC).

Kubernetes requires you to create safeguards like authentication on your own. This requires you to create bearer tokens or another authentication method manually, which is tedious and time-consuming. 

6. Support 

All three solutions offer self-service support for their open-source projects. Expect Docker Community Edition to have a larger developer community and more users than OpenShift. There is a high likelihood that you will find a Docker engineer willing to assist you if you encounter any issues.   

Red Hat's and Docker Inc.'s engineers provide dedicated support for the paid versions of OpenShift and Docker Enterprise Edition whenever you need it.

By far, the largest community belongs to Kubernetes. This makes finding a solution for any Kubernetes issue much simpler. Sorting out the discussions and suggestions might take a while, though.    

7. Updates and releases

Its colossal following contributes to its frequent updates, with up to four releases per year. Kubernetes will also alert you when a new version is available. Invoke the kubeadm upgrade command as soon as you decide to upgrade, and it will make the upgrade simple. 

Docker has the busiest update schedule of the three. One reason may be that it caters to several tools, including Docker Engine, Hub, Compose, and Docker for Windows and Mac. Expect multiple updates per item per year. 

An update from OpenShift follows almost every Kubernetes release. Red Hat releases new updates up to three times a year. There won't be any alerts to upgrade. In addition, any time you install a new release, it is handled by the Red Hat Enterprise Linux package system.  

Kubernetes and Docker support multiple updates, but OpenShift's DeploymentConfig does not.  

In all cases, you should back up your current installation before installing the upgrade. You can roll back any update if it does not work as expected.    

8. Networking

Unlike Kubernetes, which lacks a native networking solution, OpenShift's software-defined-networking (SDN) communicates seamlessly between pods in the OpenShift Container Platform. It then uses Open vSwitch (OVS) to configure an overlay network. It configures the pod network via three SDN plugins; ovs-subnet, ovs-multitenant, and ovs-networkpolicy.

Docker uses multi-host networking where you get to choose an overlay network for your services. During initialization or updates, the Swarm Manager automatically assigns addresses to the containers in the network.    

9. Templates 

OpenShift offers pre-built images, so you don't have to create them from scratch. However, some engineers find OpenShift templates less user-friendly than, for example, the simpler and more flexible Helm charts in Kubernetes. 

Helm charts enable you to use custom hooks and in-place upgrades, simplify rollbacks to older release versions, and support simple sharing. 

10. Web user interface

An easy-to-use web-based user interface will make cluster administration easier for you. 

Kubernetes’ dashboard does not have a web console or login page like Docker and OpenShift do. You can see cluster roles, servers, and projects through the OpenShift and Docker web consoles.

To secure your Kubernetes platform, you need to create one, including authentication and authorization. It is a manual process that can be daunting, depending on your Kubernetes engineering experience. 

11. Continuous integration and continuous deployment (CI/CD)

Kubernetes, OpenShift, and Docker do not offer comprehensive CI/CD tools out of the box. However, they support third-party tools such as CircleCI for building robust CI/CD pipelines in Kubernetes, Docker, and OpenShift. 

Still, OpenShift offers an integrated CI server in the form of a certified Jenkins container. Jenkins is one of the most robust, universal, and mature CI/CD tools available today.     

Which Platform Should You Use?

Kubernetes, OpenShift, and Docker are each solid in some areas and not so strong in others.

OpenShift offers superior security features, dedicated customer support, am easy-to-use web console for logins, and a choice between paid and free editions. As an open-source project, OpenShift would not limit you to just Red Hat services. Moving your enterprise somewhere else is entirely up to you. 

Docker is a tested container engine for building Docker images. It also runs hassle-free on many platforms, including Kubernetes and OpenShift. Docker Swarm allows you to do integrated cluster management within Docker. Still, Docker is not as complex as Kubernetes, which can help increase visibility into your Docker workloads. It also offers built-in security features. 

Kubernetes provides superior horizontal scaling (automatic and manual), extensibility, multi-cloud/hybrid cloud, and self-healing capabilities to help you keep your system close to your desired state at all times. 

Kubernetes is also compatible with most tools and platforms. However, Kubernetes' complexity makes it difficult to monitor when and where engineering spend goes. 

Kubernetes Cost Management Can Help

Monitoring and analyzing your Kubernetes spend gives you the insight you need to make informed engineering and product decisions that ensure profitability for your organization. 

With CloudZero Kubernetes cost analysis, engineers can see how much they spend on Kubernetes per feature, product, customer, team, and more — and even drill down into costs per cluster, pod, or namespace down to an hour.

Additionally, CloudZero tracks, detects, and alerts on cost anomalies, sending timely notifications to the right people in your organization to ensure you don't overspend on Kubernetes. Request a demo today and find out how CloudZero can help you monitor your Kubernetes costs.


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