In this age of rapid developments, more and more organizations are embarking on the cloud-native DevOps journey and migrating their infrastructure and architecture to keep pace with the cloud-native and data-driven era. This means an increasing number of digital transformation tools are being introduced frequently. As companies work toward matching this ongoing technology trend, words like cloud computing, containerization, and container orchestration have become commonplace, and their interest is increasing every day. But when we talk of cloud-native, it is very difficult to not mention Docker and Kubernetes. These are the two basic tools that facilitate a company's transformation strategy. So, you must learn to work with them comfortably. These are revolutionary tools and have changed the way we create and deploy software at scale. Let us first understand what these tools are.

Docker

Docker is primarily a platform for software development. It is a type of virtualization technology. With Docker, developing and deploying applications inside virtual containerized environments becomes easier. Docker is compatible with almost every kind of machine which means the software remains system-agnostic or you can say that the applications are independent of the Operating System (OS). With Docker, you have to do less work to develop the application and it becomes easy to deploy and maintain it thus making the use of the application simpler. With Docker, developers find it easier to run their applications in a similar environment without any dependencies because Docker containers have native operating system libraries. Earlier, the developer had no option but to send their code to the tester but because of many dependency issues, the code would not run on the tester's machine although it ran well on the developer's machine. This created a lot of confusion. But with Docker, this problem has been removed as both the developer and the tester now have the same system that runs on the Docker container. Being an open-source tool, Docker makes it possible for developers to make applications anywhere.

Developers can create Dockerfile with Docker. They use it to define the requirements of the application in it. It describes the process of building the software. When you give it to the "Docker build" command, an entrenched image is created. This image is usually the blueprint or template of the application and shows the dependencies. When the Docker image is run, it creates a Docker container which is just a run time instance of the Docker image. It can run on any environment like Mac, Windows PC, Linux, Cloud, etc. Docker also provides an online cloud repository called Docker Hub where you can store all the Docker images that you create. The Docker containerization consists of infrastructure and an operating system but lacks Hypervisor as in virtualization. The operating system on which the process runs is called Docker Daemon. This OS enables running containers on the system and manages the Docker images and all Docker commands. Therefore, we can say that the main aim of Docker is to package and containerize the applications and send them to and run them anywhere any number of times. 

Kubernetes

There are certain specific tasks that need to be handled in the Docker cluster environment like scheduling, communications, and scalability. And an orchestration tool has to be used to handle such tasks. Kubernetes is one such platform that is more popular around the globe. Kubernetes is again an open-source container orchestration platform that is used to manage, automate, and scale containerized applications. Though Docker Swarm is also an orchestration tool, Kubernetes is taken as the standard because it is more flexible and has more scaling capacity. It takes the primary container responsibilities like container deployment, scaling, healing, and load balancing of the container. Kubernetes cluster is a working deployment of Kubernetes. This Kubernetes cluster can be seen as two different parts which are the control plane or the master node and the compute machines or the worker node. Further, each of these nodes could be a physical or virtual machine and is its own Linux environment. Pods, consisting of containers are run by each node.

Since each node can be a physical or virtual machine, you can manage thousands of containerized applications in different types of environments like physical, virtual, or even hybrid machines with Kubernetes. To put it simply, Kubernetes ensures that each container is in its right place and that all of them can work together. It is not the processes that define Kubernetes but it is defined by states. It makes sure that once it has defined a pod, it keeps running always. In the case of a container getting killed or going down, Kubernetes attempts to start a new one. Kubernetes is used by companies for automating the deployment and management of containerized applications. 

Docker and Kubernetes together

Now, we have made it amply clear that Docker helps you in creating the containers while Kubernetes facilitates their management at run time. While Docker packages and ships the application, Kubernetes helps you to deploy and scale the application. So, it can be inferred that both go together. One is needed for the other to work smoothly. Smaller companies or even startups that have a lesser number of containers, can generally manage them without using Kubernetes. But wherever the number of containers is large, organizations need Kubernetes to manage them. This is because in larger companies the infrastructure is bigger and as the infrastructure becomes bigger the number of containers also rises and it becomes harder to manage them. So, the need to employ Kubernetes arises. 

When Docker and Kubernetes are used together they act as facilitators for digital transformation and this transformation becomes a lot easier as they serve as tools for modern cloud architecture. Today, it has become normal for companies to use Docker and Kubernetes for faster development, deployment, and release of applications. Just running the containers in production is not enough, they have to be regulated. Kubernetes has some really strong features that enable easier regulation of the containers. These include auto-scaling, health checks, and load balancing. All these are critical for managing the container lifecycle. Kubernetes keeps checking if the deployment has been done as per the YAML definition. Although Docker and Kubernetes work better together, it has been strongly recommended that at the time of building stacks, you should clearly understand the differences between Docker and Kubernetes. Both of them have different scopes and can be used separately also.

If seen from the viewpoint of software development, Docker's strong point is development. This means its use is to configure, create, and distribute the containers and use Docker Hub as an image registry. Kubernetes, on the other hand, works really well in operations where you can use your existing Docker containers and handle its complexities related to deployment, scaling, networking, and monitoring. 

In short, you can use Docker to isolate your containers and pack them but with dependencies. But Kubernetes will help you in the deployment and orchestration of these containers. But when you use both of these together, productivity increases and so does the confidence of everyone. Organizations use microservices to change their monolithic applications into smaller components so that they can be packaged and deployed separately. The purpose of these microservices is to help you in delivering more scalable, agile, and strong applications that you can update, change, and redeploy faster. And this is where tools such as Docker and Kubernetes help companies to do these activities in an easier and faster way. They provide the necessary flexibility to the companies to deploy and scale the applications as necessary. The use of Docker and Kubernetes is spreading rapidly and more and more companies are adopting them and using them in huge scaling of production. So, owing to their usefulness, companies all around the world are integrating these two platforms for their containers and microservices. 

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