Kubernetes vs Docker: Compare the Differences

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Containers and microservices have become the darling technology of enterprises. This is especially true if your business has adopted CI/CD and DevOps solutions or is looking to become more agile in an increasingly competitive world.

When you look to the world of containerization, two technologies rise to the top: Kubernetes and Docker. Although these two coins are on different trajectories, they are both front and center of the containerization trend, and it is very likely that you have, use or will use one or both of them.

Containers benefit businesses by providing:

  • Development and deployment of agile applications
  • IC/CD
  • DevOps software
  • Observability
  • Cloud and operating system portability
  • Application-centric management
  • True Resource Isolation

Between Kubernetes and Docker, which of these DevOps tools is best suited to meet your business needs and your DevOps workflow? Let’s find out.

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What is Kubernetes?


Kubernetes is an open-source container orchestration platform for managing, automating, and scaling your containerized applications and microservices. Kubernetes was originally designed by Google and is now managed by the Cloud Native Computing Foundation.

Kubernetes is about orchestrating large containerized deployments, not just one-off containers. Kubernetes can be deployed on a cluster of bare metal servers in your data center or on third-party cloud providers and works with a controller to manage the resources of the cluster-joined nodes. A cluster can consist of one controller and one node or one controller and up to 5,000 nodes, although it is not optimized to handle more than 500 nodes per cluster.

Once upon a time Kubernetes used Docker as its runtime. This is no longer the case, and instead Kubernetes supports Podman and Containerd runtimes.

What is Docker?

Although the purpose of Docker is similar to that of Kubernetes, these two DevOps tools are quite different. While Kubernetes focuses on large-scale deployments, Docker just deploys a single container on your network. That doesn’t mean Docker can’t work with larger deployments. Thanks to the Swarm mode, it is possible to deploy a cluster of Docker nodes and deploy your containerized applications and microservices at scale.

An important aspect of Docker is that it offers a much lower learning curve than Kubernetes. Anyone looking to get started in the world of containers would do well to start with Docker and work your way up to Kubernetes. And even though the list of DevOps tools is quite extensive, these two technologies are among the most important.

Direct comparison: Kubernetes and Docker

Container management

Kubernetes and Docker are used to deploy and manage containers. Kubernetes, by default, operates as a cluster of nodes where the containerized application can be scaled as needed. Docker, on the other hand, is a container runtime that is as comfortable deploying a single container on a single node as it is deploying full applications on a cluster (called Docker Swarm).

Docker primarily focuses on developing, sharing, and running individual containers, while Kubernetes focuses on large-scale containerized applications.

Controllers and Nodes

Although Docker does not require the deployment of controllers and nodes, if you plan to use Docker Swarm, you will need to use both a controller and multiple nodes.

Kubernetes, on the other hand, requires the use of both controllers and nodes. These controllers and nodes can be off-the-shelf servers in your data center or hosted by third-party cloud providers, such as AWS, Azure, Google Cloud, Rackspace, and Linode.

development tools

Kubernetes and Docker contain all the tools you need to develop your containerized applications. Both depend on image registries (such as those hosted on Docker Hub) and use JSON-formatted manifests to layout portable and containerized applications. Both offer command-line interface tools for development, as well as several third-party GUI tools.

Kubernetes and Docker can be integrated with your current development tools, such as your favorite IDEs and versioning systems such as git.

Groups

As I said, both Kubernetes and Docker can use clusters. The difference is that Kubernetes requires a cluster, while a Docker Swarm is optional. This also highlights the biggest difference between Kubernetes and Docker: Kubernetes scales much easier and more widely than Docker.

Persistent Volumes

When you deploy a containerized application, chances are it depends on saved data. Fortunately, Kubernetes and Docker can use persistent volumes. These volumes save data outside of the container so that if anything were to happen to the running containers, the data is saved in its own persistent volume.
Persistent volumes also allow data to be shared between containers. For example, you can deploy a MySQL container using a persistent volume and connect multiple containers to that database.

Containers vs. Pods

Docker deploys containers, which are containerized applications and microservices. Kubernetes, on the other hand, actually encapsulates containers in pods, which are a top-level structure that can contain multiple containers that share the same resources. Care must be taken not to deploy too many containers on a single pod, as these containers must scale together, which could waste resources.

Although Docker does not work with pods, it is possible to deploy complete applications using individual but interconnected containers.

Networking

One area where Docker really shines is networking. You can easily deploy a container with Docker and immediately and easily access it from a network.

Kubernetes, on the other hand, isolates pods from the outside world. For this reason, you must add an Ingress or LoadBalancer controller to access these containerized applications from outside the cluster.

Feature comparison: Kubernetes and Docker

FeatureKubernetesDocker
FacilityDifficultSimple
learning curveTo soakShallow
ScalingAutomatiqueManual
SurveillanceIntegratedRequires third-party tools
load balancingManualAutomatique
CLI toolsIntegratedIntegrated
Execution engineRequires third-party toolsIntegrated
GroupingIntegratedMust be deployed in cluster mode (Docker Swarm)
Recommended node sizeUp to 500 knotsRecommended maximum of seven manager nodes for a swarm

What is the best container tool?

The answer to this question depends on your needs. If you want to take your first steps with containerized applications and microservices, you should definitely start with Docker. And if you’re looking to deploy a single container on a single node or a small cluster, Docker is again your best bet. However, if you are a large enterprise looking to deploy containerized applications at scale, Kubernetes is for you.

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