Kubernetes vs. Docker: 5 Key Differences and How to Choose

What Is Docker? 

Docker is a platform that enables developers to package, deploy, and run applications in lightweight, portable containers. This technology isolates applications from their environment, ensuring that they work uniformly despite differences in development and staging environments. 

By using Docker, developers can eliminate the common issue of inconsistencies and operational issues due to variations in operating systems and underlying infrastructure. Containers ensure that applications run exactly the same across all environments. In addition, Docker containers are faster, more efficient, and less resource-intensive than traditional virtual machines.

Docker containers allow for rapid application deployment and scaling, providing a consistent environment from a development environment to the production server. This consistency significantly reduces the time and effort required to develop, test, and deploy applications, streamlining the software development lifecycle. 

How Docker Containers Work 

Docker containers operate by packaging an application and its dependencies into a single container image. This image contains everything the application needs to run, including the code, runtime, libraries, and environment variables. 

When a container is run from an image, Docker uses the host operating system’s kernel but isolates the container’s process and file system. This isolation is achieved through kernel features such as namespaces and cgroups, which limit and allocate resources like CPU, memory, and I/O separately for each container.

Unlike virtual machines that require a full operating system to run each application, Docker containers share the host OS kernel and run as isolated processes, ensuring lightweight and fast operation. This efficient use of system resources allows for a high density of containers on a single host, maximizing utilization and minimizing overhead. The ability to quickly start, stop, and replicate containers makes Docker ideal for scaling applications in response to demand.

Key Benefits of Using Docker

Here are some of the key benefits of using Docker for application deployment:

• Rapid deployment: Containers can be created, started, stopped, and destroyed in seconds, allowing for quick iterations and development cycles.
• Consistency across environments: Applications packaged in Docker containers run the same way in any environment, eliminating the “it works on my machine” problem.
• Efficient use of system resources: Containers share the host system’s kernel, making them much lighter and more efficient than virtual machines that require a full OS.
• Isolation: Containers are isolated from each other and the host system, easing operations and reducing conflicts between applications.
• Version control for containers: Docker images are versioned, making it easy to roll back to previous versions of an application if needed.
• Ecosystem and tooling: A vast ecosystem of tools and services has developed around Docker, providing additional functionality such as monitoring, networking, and security.

What Is Kubernetes? 

Kubernetes, often referred to as K8s, is an open-source platform designed to automate deploying, scaling, and operating application containers. Developed by Google and now maintained by the Cloud Native Computing Foundation, Kubernetes provides a framework for running distributed systems resiliently, allowing for scaling and failover for your applications. 

Kubernetes supports a range of container engines, including Docker, and enables the ability to manage containerized applications in various environments, including physical, virtual, cloud-based, and hybrid infrastructures. It simplifies many aspects of running containerized applications, from managing resource utilization and scalability to providing storage and networking orchestration. 

Kubernetes is a powerful Open-Source platform that streamlines the process of creating and deploying applications quickly and efficiently.. This ability to automate many operational tasks associated with container management has made it a popular tool for modern DevOps practices.

Note: As of the time of this writing, Kubernetes does not officially support Docker containers, although Docker containers can still be used in Kubernetes. It is common to use Docker in development environments but use more lightweight container engines, like containerd, when running them in Kubernetes.

How Kubernetes Works 

Kubernetes orchestrates clusters of virtual machines and schedules containers to run on those machines based on the available resources and the requirements of each container. Containers are grouped into pods, the basic operational unit in Kubernetes, which can then be managed as a single entity, simplifying deployment and scaling. 

Kubernetes manages the lifecycle of pods, automatically starting, stopping, and replicating them based on the defined policies and the state of the system. It also manages networking between containers, allowing for seamless communication within and outside the cluster. It provides mechanisms for service discovery, load balancing, and securing container communications. 

Additionally, Kubernetes offers storage orchestration, allowing containers to automatically mount the storage system of choice, whether from local storage, public cloud providers, or network storage systems.

Benefits of Using Kubernetes 

Here are some of the key benefits of Kubernetes for containerized applications:

• Automated scheduling and self-healing: Kubernetes automatically places containers based on their resource requirements and other constraints, while not sacrificing availability. It restarts, replaces, and reschedules containers when they fail.
• Load balancing and service discovery: Automatically distributes network traffic so that the deployment is stable. Kubernetes provides containers with their own IP addresses and a single DNS name for a set of containers, facilitating load balancing.
• Horizontal and vertical scaling: Ability to scale applications up, down, or across multiple physical machines fully automatically, or using simple CLI commands or API calls.
• Automated rollouts and rollbacks: Kubernetes progressively rolls out changes to your application or its configuration, monitoring application health to prevent downtime.
• Secret and configuration management: Kubernetes lets you store and manage sensitive information, such as passwords, OAuth tokens, and ssh keys. You can update and deploy secrets without rebuilding container images and without exposing them in your stack configuration.
• Storage orchestration: Automatically mount a storage system of your choice, whether from local storage, public cloud providers, or a network storage system.

This is part of a series of articles about Kubernetes monitoring.

Kubernetes vs. Docker: Key Differences 

Kubernetes and Docker serve different, albeit complementary, roles in the container ecosystem. 

1. Primary Functions

Docker focuses on creating and managing containers, providing the tools necessary to build and containerize applications efficiently. It simplifies the process of packaging applications into containers, ensuring they can run consistently across different environments. 

Kubernetes is a container orchestration platform, designed to manage large-scale containerized applications. It handles the deployment, scaling, and operation of containers across clusters of machines, providing the infrastructure needed to run complex distributed systems.

2. Scope and Use Case

Docker is primarily used for containerization—encapsulating applications in containers to ensure portability and consistency. It is suited for both development and production environments but on its own does not offer advanced management features for handling large numbers of containers.

It should be noted that Docker Swarm, a container orchestration solution, is offered as part of the broader Docker platform. Swarm is comparable to Kubernetes, but is much more limited in its capabilities. It can be suitable for managing smaller or less complex containerized environments.

Kubernetes is used for orchestrating large-scale containerized applications, focusing on how containers are deployed, scaled, and managed in production environments. It excels in scenarios where applications need to be scaled dynamically and maintained with high availability. It is battle-tested in high-scale, demanding production environments.

3. Features and Capabilities

Docker, though it offers some orchestration features through Docker Swarm, primarily excels in building, shipping, and running containerized applications, focusing on the individual container lifecycle. 

Kubernetes’ features include automated rollouts and rollbacks, resource management, service discovery and load balancing, secret and configuration management, storage orchestration, and security. These capabilities make Kubernetes well-suited for managing complex, microservices-based architectures at scale. 

4. Complexity and Learning Curve

Docker’s simplicity and straightforward approach to containerization make it relatively easy to learn and integrate into development workflows. 

Kubernetes, given its extensive feature set and operational capabilities, presents a steeper learning curve. Managing a Kubernetes cluster involves understanding concepts like pods, services, deployments, and replicas, and multiple software components like the API Server, etcd database, the kubelet management agent, and controllers, which can be challenging for newcomers.

5. Community and Ecosystem

Docker’s widespread adoption has fostered a rich ecosystem of tools, extensions, and integrations that enhance its capabilities. 

Kubernetes, backed by the Cloud Native Computing Foundation, has seen rapid growth in its community and ecosystem, with a vast array of tools, services, and platforms built to support Kubernetes environments. 

Related content: Read our guide to Kubernetes monitoring tools

Docker or Kubernetes: Which One Is Right For You? 

When choosing between Docker and Kubernetes, use the following considerations:

1. Project scale and complexity: For simple, smaller-scale projects or for development environments, Docker may be sufficient. For larger, more complex applications, especially those requiring high availability and scaling, Kubernetes is more suitable.
2. Resource availability and management: Docker is less resource-intensive and can be simpler to manage for small deployments. Kubernetes offers more robust management features for complex deployments but requires more resources and a steeper learning curve.
3. DevOps maturity: Organizations with mature DevOps practices may find Kubernetes’ advanced features more beneficial for automating and optimizing their workflows.
4. Future needs and scalability: Consider not just your immediate needs but also potential future requirements. Kubernetes offers more flexibility and scalability for growing applications.
5. Learning curve and team expertise: Docker’s simplicity makes it easier to learn, which might be suitable for teams with less containerization experience. Kubernetes, while more complex, offers extensive documentation and community support to help teams ramp up.

Many organizations opt to use Docker and Kubernetes together, leveraging the strengths of both to create an effective container management solution. Docker simplifies the process of packaging and containerizing applications, ensuring that they can run consistently across different environments. Kubernetes, on the other hand, excels in orchestrating these containers, managing their deployment, scaling, and operations across clusters of machines. 

Using Docker and Kubernetes together is beneficial because it harnesses Docker’s efficient and easy-to-use containerization platform with Kubernetes’ robust and scalable container orchestration system. This integration enables a streamlined workflow where applications are easily packaged, deployed, and managed, allowing for quicker development cycles, more efficient resource use, and higher availability of applications.

Kubernetes Monitoring and Troubleshooting with Lumigo

Lumigo is a troubleshooting platform, purpose-built for microservice-based applications. Developers using Kubernetes to orchestrate their containerized applications can use Lumigo to monitor, trace and troubleshoot issues fast. Deployed with zero-code changes and automated in one-click, Lumigo stitches together every interaction between micro and managed service into end-to-end stack traces. These traces, served alongside request payload data, give developers complete visibility into their container environments. Using Lumigo enables the ability to:

End-to-end virtual stack trace across every micro and managed service that makes up an application, in context

• API visibility that makes all the data passed between services available and accessible, making it possible to perform root cause analysis without digging through logs 
• Distributed tracing that is deployed with no code and automated in one click 
• Unified platform to explore and query across microservices, see a real-time view of applications, and optimize performance

To try out more about Lumigo for Kubernetes, check out our Kubernetes operator on GitHub