Tech Insights / Kubernetes vs. Docker

Kubernetes vs. Docker:
Differentiating container orchestration, architectures and runtimes

As Kubernetes and containers continue to grow in popularity, organizations often ask whether they should choose Kubernetes or Docker. This question makes it sound as though the two technologies are interchangeable, but it makes more sense to think of them as complementary. This article explains the capabilities of Kubernetes vs. Docker, including comparisons between Kubernetes versus Docker Swarm and Docker Compose.


What is Kubernetes vs. Docker, exactly?

Docker is a software platform for creating containerized applications, while Kubernetes is a container orchestrator that simplifies and automates the process of running containerized applications at scale. Organizations often ask, “What is Kubernetes vs. Docker?” but it is best to think of them as complementary technologies, not competing ones.

Companies often use Docker and Kubernetes together, with distinct differences in when and how the two technologies are used:

  • Docker is used to build, distribute, and run containers. However, by itself, Docker is not well suited for complex applications consisting of multiple instances of multiple containers.
  • Kubernetes is a platform that works with Docker containers or other Open Container Initiative (OCI)-compliant containers to automate and manage the operation of containerized applications at scale, while providing tools, monitoring and security across clouds.

Docker also has several advanced components that offer some “Kubernetes-like” functionality for specific use cases: a container orchestrator called Docker Swarm and another tool to run multi-container Docker apps on a single host called Docker Compose (more on these later).

Benefits of Kubernetes vs. Docker

Both Kubernetes and Docker can provide significant benefits for organizations that want to create and run modern, container-based applications.

Kubernetes enables you to:

  • Take advantage of a large and growing ecosystem. An enormous ecosystem of tools (many of them open source) has evolved around Kubernetes, integrating important technologies such as cloud native security, policy-based management, and platform monitoring and alerting.
  • Improve developer productivity. DevOps teams can achieve significant increases in productivity with integrations between Kubernetes and tools that reduce the complexity of the development environment, shorten release cycles for cloud native software, and improve software quality by streamlining engineering workflows. VMware’s State of Kubernetes 2023 survey shows that 60% of organizations found Kubernetes helps developers to be more productive, and 64% believe Kubernetes is making IT operators more efficient.
  • Multi-cloud deployment. Kubernetes workloads can run in a single cloud or across multiple cloud services. All major cloud vendors (e.g. Google, Microsoft Azure, AWS) support Kubernetes. Kubernetes’ portability allows organizations to run in multi-cloud environments and avoid vendor lock-in.
  • Make apps more reliable and available. Kubernetes enables high availability for applications. It also allows rolling updates, so software changes can be made without scheduling downtime. Kubernetes can simplify the migration of apps from monoliths to microservices.
  • Scale as needed. Kubernetes autoscaling simplifies resource management by scaling infrastructure on demand. Kubernetes can increase the resources available to an application during peak times and scale them down during less busy times, lowering costs.

Docker enables organizations to:

  • Create code that works on any machine. Containers eliminate the problem of testing code in one environment and then not having it work in other environments due to different configurations and settings.
  • Provide a uniform environment. Everyone uses the same Docker container with the same setup, allowing teams to run scripts and establish processes that simplify life for development and operations teams. IT can more easily isolate and eliminate environment issues without needing to know how individual machines are set up.
  • Centralize resources. Teams can store and access large numbers of container images for free from Docker Hub or other public or private container registries.
  • Improve deployment speed. Docker images are small and self-contained and use less resources than virtual machines (VMs), accelerating delivery and reducing container deployment time.



Making the call: The Important differences between Kubernetes vs. Docker

Container orchestrators such as Kubernetes help manage the complexity of the container lifecycle. This becomes especially important when you’re operating distributed applications with large numbers of containers across multi-cloud environments.

Kubernetes automates deployment, load balancing, resource allocation, observability and security enforcement for containers via declarative configuration and automation. It keeps containerized applications running in the desired state, ensuring they are scalable and resilient.



What are the differences between Docker and Kubernetes?

Kubernetes
Docker
What does it do? Kubernetes is an orchestration system for running containers. It automates the process of deploying, operating and scaling containerized applications. Docker is a platform for creating containerized applications. Applications can be run manually using the Docker runtime or via an orchestrator.
When do you use it in the application lifecycle? Kubernetes is used after an app has been packaged into containers to orchestrate and manage the execution of the containers that make up the app. Docker is used to package code and dependencies into containers as you build and test applications. The resulting containers can be run using the Docker runtime or another OCI-compliant runtime.
How does it work? Kubernetes groups together containers that make up the same application. Each container needed for an application may have multiple replicas, and incoming requests are distributed by load balancers across the replicas. Kubernetes oversees the containers that make up each running application, making sure that they operate properly as they are deployed. A Docker container image is a standardized software package that includes everything you need to run an application: code, runtime, system tools, system libraries, and settings. It can be deployed manually, using Docker Compose, or using an orchestrator like Kubernetes or Docker Swarm.


Container orchestration, architecture and runtime details to keep in mind

The Docker environment includes a container runtime as well as build and image management. Docker remains a very popular tool for creating containers, while Kubernetes has become the most popular tool for container orchestration in production.

Does Kubernetes still use Docker?

Kubernetes and Docker can be used together or individually; neither absolutely requires the other. Kubernetes orchestrates OCI-compliant containers created by Docker and other tools, such as Tanzu Build Service. Kubernetes requires OCI-compliant containers and an OCI-compliant runtime environment.

The Docker runtime is not entirely OCI-compliant, but it can be used with Kubernetes. In the past, it required an additional program, dockershim, to run in Kubernetes. The dockershim code has been removed from Kubernetes and shifted to the Container Runtime Interface (CRI), which supports a broader set of container runtimes with smooth interoperability between different runtimes.

Because Docker builds an OCI-standard container image, those images will run on any OCI-compliant container runtime. Therefore, developers can continue to use Docker to build, share and run containers on Kubernetes.

Containers vs. Kubernetes vs. Docker

Kubernetes is sometimes used as shorthand for a full container environment with both Docker and Kubernetes. But it’s best not to think in terms of “Docker vs Kubernetes” since they perform different functions. Kubernetes schedules and automates the management and deployment of Docker containers—or any OCI or CRI-compliant container—on Kubernetes clusters across diverse platforms.

Should I use Docker or Kubernetes?

When containers began to become popular, Docker was almost synonymous with containers, and it continues to be popular with developers. If your organization has significant investments and expertise in Docker, it makes sense to use it to create OCI-compliant containers, whether you’re running Kubernetes or not.

When to use Kubernetes is really a matter of scale. If you’re running complex, multi-container applications—and want to ensure availability and scaling by adding multiple container instances quickly—you will almost certainly choose Kubernetes. Kubernetes was designed specifically to address the operational concerns of running containers in production. It recognizes the anticipated—and unanticipated—complexities of running containers on different systems and in different environments.

However, there may be some situations where Docker Compose and Docker Swarm make sense.

Docker Compose vs. Kubernetes

Docker Compose is a tool designed to manage multi-container applications, using a simple YAML file to configure and deploy multiple Docker containers running on a single server rather than on a cluster. If you need to deploy multiple containers as a single service running on a single host, Docker Compose is a viable solution.

Docker Swarm vs. Kubernetes

A comparison of “Docker Swarm vs. Kubernetes” is more apt than “Docker vs. Kubernetes” since both are container orchestrators. Docker Swarm is a cluster manager for Docker containers that focuses on clustering Docker containers and is tightly integrated into the Docker ecosystem, with its own API and CLI. Docker Swarm can orchestrate containers for smaller workloads. Docker Swarm is built into the Docker Engine and runs inside Docker containers. Kubernetes works with multiple frameworks and languages across environments. Complex applications running at scale usually benefit from the more extensive capabilities and flexible ecosystem of Kubernetes.

Tanzu vs. Kubernetes and Docker

It's the ecosystem that surrounds Kubernetes that makes it what it has become today. Kubernetes is able to deliver operational efficiency, developer productivity, and—according to State of Kubernetes 2023—significant business benefits. To get those benefits, you have to make sure the tools you choose work together well.

Tanzu offers an integrated stack based on open source components, Kubernetes and VMware technology, with automated tools designed to simplify platform operations across clouds. Tanzu offers solutions that help eliminate the complexity of containers and Kubernetes. Tanzu solutions help you build, deploy and manage containerized applications, improve developer productivity, and deliver software more quickly and securely.



Building on Kubernetes with Tanzu

Kubernetes is essential for companies making the transition to cloud native development. Tanzu prepares your platform engineering and development teams for modern containerized applications with consistent, conformant Kubernetes everywhere, with centralized lifecycle and policy management of all your Kubernetes clusters on-premises and in the cloud.

Tanzu Application Platform simplifies and secures the container lifecycle to speed the delivery of modern apps at scale. With its modular, full-stack capabilities, you can embrace DevSecOps and stand up a platform for modern apps that ensures security throughout the container lifecycle. Automatically build a stream of compliant containers and secure your software supply chain from end to end.

Tanzu for Kubernetes Operations provides a simplified, consistent approach to container deployment, scaling, and management with tools, automation, and data-driven insights.

Tanzu Mission Control is a centralized Kubernetes management platform that provides a single point of control to manage your entire Kubernetes footprint across multiple environments. It provides centralized lifecycle management, identity and access management, policy management, cluster inspections and data protection.

Tanzu Observability is a unified observability multi-cloud management solution with single-source-of-truth visibility and contextualized information across logs, metrics, and traces for greater business agility while maintaining SLAs.

Tanzu Labs can help you to transform your teams and your applications, while streamlining operations across multi-cloud infrastructure. Tanzu Labs works with your teams to build apps, modernize apps, and develop platforms, while empowering them to learn about Kubernetes and related technologies.

VMware also offers KubeAcademy, a free, product-agnostic Kubernetes and cloud native technology education platform. It provides an accessible, self-paced, learning path to advance skill sets along the Kubernetes journey.