Containerization has gained immense popularity these days as it provides a lot more advantages over traditional virtualization. Efficient, lightweight, close parity with the development environment, and much faster, the concept of containerization leverages kernel level isolation. You can run containerized applications anywhere without any dependency on a full-fledged virtual machine. In brief, we can compare this to operating-system-level virtualization. 

In this context, Docker and Kubernetes have achieved significant attention in the industry for encapsulating applications in their self-contained environments. However, Kubernetes vs Docker is the most hyped discussion. Interestingly, Kubernetes vs Docker is often seen as rivals, although they have their own pros and cons.

In the realm of Kubernetes vs Docker, these two players have a difference between their fundamental technologies.  Docker platform enables users to build, distribute, and run Docker containers. On the other hand, we can use the Kubernetes system for Docker containers, which makes Kubernetes one step ahead in the competition. 

However, before we dig into Kubernetes vs. Docker’s comparison, we must know the basic concepts of the Docker platform and Kubernetes.

Related post – Amazon EKS – Managed Kubernetes service

What is Docker Container

The most popular container platform at the recent time, Docker, was open source from the beginning. This is one of the reasons that the Docker platform dominates the current market. It has its native clustering tool for orchestrating and scheduling containers on machine clusters. Docker features the Docker Engine. This is a runtime that allows to build and run containers. Besides, it includes Docker Hub, a service registry for service discovery and storing and sharing Docker images. 

Below are some of the purposes why use Docker for containerization.

– Docker streamlines the development lifecycle using local containers for applications and services. So, it is ideal for CI/CD workflows (continuous integration and continuous delivery). Besides, it assures consistent yet fast delivery of applications.

– The container-based Docker platform allows highly portable workloads. Such containers can run on physical, virtual machines and even in a data center. Furthermore, these containers are scalable and responsive and compatible with mixed environments or cloud environments. 

– Docker is lightweight, so it allows more compute capacity. Besides, this is a cost-effective solution. In high-density environments where we need small and medium deployments, the Docker platform is an ideal solution. It can run more workloads on the same hardware.

Docker architecture

Docker architecture is a client-server model.  Docker engine has these major components:

• Server
• REST API
• Command-line interface (CLI) client

The key components in a Docker’s architecture are as follows:

– Docker daemon: Docker daemon is a computer program that runs in the background. Known as dockerd, this persistent process manages Docker containers and operates container objects.

– Additionally, the client communicates with the Docker daemon using REST API via UNIX sockets or a network interface. Docker daemon provides a command-line interface (CLI) for communication between the users and Docker Engine API. Additionally, the daemon manages the containers, images, storage volumes, networks and communicates with other daemons.

– Docker client: User interacts with the Docker through Docker client. Using Docker API, which is Docker CLI, the client can send application commands for application execution. The client can communicate with multiple daemons at a time, no matter whether it is on the same host or a remote host. 

– Images: These are a read-only binary template that helps in building containers. They also contain metadata, which shows the capabilities and needs of the container. Images have significant dominance in configuration management of the container. For example, it can build a container on its own. Similarly, it can add additional elements on top of the existing configuration. Furthermore, to ship and store applications, it plays a significant role.

– Objects: These are entities like images, containers, and services for assembling an application.

– Container: It is the runnable environment with encapsulation or instance of a Docker image. The container runs applications. Furthermore, the Docker API or CLI manages it.

– Services: It is a collection of dockerds that allows containers to scale across multiple dockerds. When services work collectively, it is known as a swarm. Also, it communicates via the Docker API with numerous managers and workers.

– Registries: It provides locations from where we can store and download images. In other words, it is the repository of Docker images. Clients connect to registries for downloading or uploading images. Registries can be public or private. For example, public registries are Docker Hub and Docker Cloud. 

– Docker Swarm: It is a native clustering solution where a group of Docker engines turns into a single virtual Docker Engine. Leveraging its API, Docker swarm enables users to list nodes in a cluster, create discovery tokens, and run Swarm containers.

What is Kubernetes?

Kubernetes vs Docker debate arises where the limitations of the Docker platform come into the picture. And what are those most significant constraints? 

• Coordination and scheduling related issues of the containers. 
• Communication issues between the containers in the application
• Problem related to scaling up the container instances

Kubernetes is the answer for orchestrating Docker containers and is more extensive than Docker Swarm. Also, it coordinates clusters. Developed by Google, Kubernetes reflects Google’s years of expertise in container management. However, Kubernetes has now been donated to Cloud Native Computing Foundation (CNCF) and is open source. Though Kubernetes itself is not a complete solution and needs custom plugins, it can run a Docker easily build on it.

Kubernetes follows a master-slave architecture. Usually, a Kubernetes cluster comprises one master and multiple compute nodes. The master node manages the cluster. Besides, it schedules deployments and exposes the API. On the other hand, the compute node runs a container runtime alongside an agent. This agent constantly communicates with the master.

Kubernetes ecosystem consists of pods, which are scheduling units. Pods can contain one or more containers. Besides, these remain distributed among nodes and provide high availability. 

Kubernetes has many benefits like – 

• It is cloud-agnostic, which means its design is suitable for the on-premises data center and a cloud. 
• It provides a stable environment. Thus once we can make an application, it keeps alive even, it fails execution.
• Kubernetes deploys applications within seconds.
• Easy to integrate applications, monitoring, and logging activities
• Highly scalable.
• Automates deployment
• Easy to schedule containerized applications
• Comprise of a vibrant community.

However, Kubernetes itself has some limitations like –

• Administrative overheads like installation and configuration of Kubernetes master and worker nodes.
• There should be at least three Kubernetes master nodes in the running state for high availability, load balancing, and failover.
• Adequate expertise to handle master nodes.

When compared with Docker, Kubernetes vs Docker is a highly debatable point. They are very compatible with each other, facilitating container management and deployment in a distributed architecture. Thus Kubernetes vs Docker points come from how they work, i.e., containerize rather than what they are. 

Kubernetes vs Docker – Points to consider

The debut on Kubernetes vs Docker arise from the below perspectives –

• Installation and cluster configuration
• GUI
• Scalability
• Auto-scaling
• Load balancing
• Data Volumes
• Rollback and rolling updates
• Logging and monitoring

Final thought:

To conclude, Kubernetes vs Docker – rather than compete, they rely on each other on the road to success. Comparing Kubernetes vs. Docker, Kubernetes is a more comprehensive solution than Docker Swarm. Thus users can easily build on top of Kubernetes clusters. However, with their own pros and cons, both Docker and Kubernetes are here to stay. With more trending technologies like Microservices, multi-cloud computing, and app modernization, these two container management technologies are also continuously changing. This will transform them to make the right fit in the future.