Docker vs. Kubernetes

Introduction

If you are just getting acquainted with containers and container orchestration tools, you may find yourself thinking about the difference between Kubernetes and Docker. Comparing these two tools is not a straightforward process as they are not competitors nor do they have the same roles.

In this article, you will learn about Docker and Kubernetes, how they differ, and how they are related.

Docker vs Kubernetes Explained

It is a common misconception that there is a clear juxtaposition between Docker and Kubernetes. The truth is that a head-to-head comparison isn’t possible as one software cannot replace the other.

Both platforms are popular container technologies. Docker is a containerization tool, while Kubernetes is a container orchestration tool. Therefore, you cannot use Kubernetes without utilizing a container, such as a Docker container.

Read on to learn more about Docker and Kubernetes, their architecture, and what they are used. This will help you understand why there is no clear comparison between the two.

What is Docker?

Docker is an open-source containerization platform used for creating, deploying, and managing applications in lightweight packages called containers. It has revolutionized and removed many tedious processes of software development and remains the leading container platform today.

Containers provide an isolated environment for packaging apps. As they virtualize resources of the underlying hardware, they are lightweight, flexible, and cost-effective. Therefore, one server can host multiple containers, each running a different app.

Although containers are similar to virtual machines, they differ by an additional virtualization layer since they utilize the kernel and operating system of the host.

How Does Docker Work

To understand how Docker works, you need to get acquainted with its main components and the role they play in the platform:

• The Docker daemon (dockerd) is a service that runs on the host and listens to Docker API requests. This continuous process manages Docker objects and communicates with other daemons.
• The Docker client is a component that provides a command line interface (CLI) for interacting with Docker and instructing dockerd which commands to carry out.
• Docker objects are elements necessary to construct the applications. They include Docker images, containers, volumes, networks, and other objects.
• Docker Registries are content delivery systems that store Docker images. You can set up and use a private registry or use Docker Hub, a public registry from which Docker pulls images by default.

The process begins with a script of instructions, called a Dockerfile. The file outlines how to create a Docker image and automatically executes the outlined commands.

All Docker containers are created from Docker images representing templates of an application at a specific point in time. The source code, dependencies, libraries, tools, and other files required for the application to run are packages into the image.

Once you spin up a Docker container from the specified Docker image, you can use it as a stable environment for developing and testing software. Containers represent portable, compact, isolated run-time environments that you can easily start up. As quickly as you can spin up new containers, you can also delete old ones.

What is Docker Used For

Docker is used as a practical tool for packaging applications into lightweight, portable units (containers). Since a container consists of all the needed libraries and dependencies for a particular application, developers can easily pack, transfer, and run new app instances anywhere they like.

Additionally, Docker and other virtualization solutions are crucial in DevOps, allowing developers to test out and deploy code faster and more efficiently. Utilizing containers simplifies DevOps by enabling continuous delivery of software to production.

Containers are isolated environments meaning developers can set up an app and ensure it runs as programmed regardless of its host and underlying hardware. This is especially useful when working on different servers as it allows you to test out new features and ensure environment stability.

Advantages and Drawbacks of Docker

Take a look at the main pros and cons of using Docker.

Advantages:

• It is simple and fast to spin up new container instances.
• Consistency across multiple environments.
• Isolated environments simplify debugging.
• Large community support.
• Containers are lighter and use less resources than virtual machines.
• The platform supports CI/CD.
• The ability to automate repetitive tasks.

Disadvantages:

• Possible security issues if containers are not secured properly.
• Potential performance issues in non-native environments.
• Since containers share the host kernel, they are not entirely isolated environments.
• Cross-platform compatibility limitations.
• Not suitable for applications that require rich interfaces.

What is Kubernetes?

Managing a large number of containers across multiple environments is a tedious task when done manually. Kubernetes (also known as k8s) automates scaling, deploying, and managing applications. It is an open-source container orchestration system for automating container management.

With a framework such as Kubernetes, you can run distributed systems of containers without worrying about downtime. You can deploy multi-container apps and ensure containers are synchronized and resource-efficient.

How Does Kubernetes Work?

The basic Kubernetes components and their role in this orchestration tool include the following:

• A Kubernetes cluster is a set of node machines for running containerized applications. The cluster consists of a control plane and one or more computing machines.
• The manifest file is a basic file that defines the general framework for a particular Kubernetes cluster and instructs the software on how you want your cluster to look like.
• Kubectl is the command-line interface used for communicating with the API server. It provides instructions to the server and directly manages resources, adding and removing containers when needed.
• The master node is responsible for load balancing workloads and establishing and maintaining communication inside the cluster. Additionally, it assigns and administers tasks to Worker Nodes.
• Worker nodes are machines for deploying containerized workloads and storage volumes. A Kubernetes cluster consists of a single Master Node and multiple Worker Nodes, where each has its task.  
• A pod is the simplest Kubernetes object that consists of multiple containers that belong to the same node. Containers deployed within the same pod share resources such as their hostname, IP address, and IPC.

Each Kubernetes cluster has two parts – the control plane and the nodes (physical or virtual machines). While the control plane manages the cluster to ensure it is in the prescribed state, the nodes run pods consisting of multiple containers running an application.

Developers instruct the control plane which commands to run on the nodes. The control plane then assigns the task to a particular node. Finally, a pod inside the node is automatically chosen to perform the task based on the workload and resources required.

Learn more about clusters, nodes, and automating container processes in our introduction to Kubernetes Architecture.

What is Kubernetes Used For

The platform is used for managing applications consisting of multiple containers that require synchronization and maintenance. Therefore, its central role is to replace repetitive manual functions with automated processes administered by the orchestration platform.

Additionally, k8s allows you to create and run applications across multiple platforms. Therefore, developers use it to avoid infrastructure lock-ins. The orchestration tool can manage and run physical or virtual containers on-premise or in the cloud, providing additional resource flexibility.

Automating deployments and scaling, contributes to faster delivery and testing and supports continuous integration and continuous delivery by shortening the software development life cycle. For this reason, it is often used by DevOps teams working with a microservice architecture.

Advantages and Drawbacks of Kubernetes

Take a look at the main advantages and disadvantages of Kubernetes.

Advantages:

• Simplifies rolling updates, canary deployments, horizontal autoscaling, and other deployment operations.
• Automated processes help speed up delivery and improve general productivity.
• Its ability to run across multiple environments eliminates infrastructure lock-ins.
• Provides the foundation for working with cloud-native apps.
• Its features support high availability, low downtime, and overall more stable applications.

Disadvantages:

• The complexity of the platform is not efficient for smaller applications.
• Migrating a non-containerized application onto the Kubernetes platform could be quite challenging.
• Due to its complexity, there is a steep learning curve that may initially reduce productivity.

How Do Docker and Kubernetes Work Together?

After reading how both container tools work, you can understand why they cannot be compared. Instead of contrasting features, you should see them as complimentary. Docker and Kubernetes work together to provide an efficient way to develop and run applications.

Ultimately, you pack and ship applications inside containers with Docker, and deploy and scale them with Kubernetes. Utilizing both technologies helps you run applications that are more scalable, environment-independent, and robust.

Conclusion

After reading this article you should understand how Docker and Kubernetes differ, whether they are comparable, and how they compliment each other when developing applications with container technology.