As the world goes into technological advancement, the selection between container technologies, such as Kubernetes and Docker, emerge as open-source leaders. The debate between Docker vs Kubernetes is common in the containerization world. However, rather than comparing these two powerful technologies, one can use these technologies to complement each other. Basically,Kubernetes and Docker are not the same, but are closely related. While working with Kubernetes, we may often be dealing with Docker.
In today’s world, containers have achieved a dominant position by public acceptance. According to one of the reports, people have used 92 % of containers in production in 2020, up from 28% recorded in 2016. Kubernetes does not make containers; it relies upon an orchestration technology such as Docker to create them. In simple words, Docker is an innovation for creating and running containers, whereas Kubernetes is used to manage containers.
To start with the fundamentals of Kubernetes and Docker, it is better to start with a technology that ties these together, namely containers.
What are containers?
Containers are an effective form of virtualization. Containers are capable of running an application by keeping it isolated from the rest of the system. In simple words, containers are the executable units of software where the application code is packaged, along with its libraries and dependencies such that it can be deployed easily and consistently regardless of the target environment such as a private data center, a public cloud, or even a developer’s personal laptop.
To understand the containers in simple words, it is better to compare them with virtual machines (VM). The containers and virtual machines work on a similar technology called virtualization. A container virtualizes an OS, whereas the virtual machines are used to virtualize physical hardware. A container packages all the libraries and dependencies in order to abstract it from the infrastructure it runs on, while the virtual machines consist of a copy of the host OS, a virtual copy of hardware to run the particular OS, and the application with all the libraries and dependencies.
Containers are an effective form of virtualization. Containers are capable of running an application by keeping it isolated from the rest of the system.
Kernel features such as namespace and cgroups are used to access resources while working with containers whereas hypervisors are used for virtual machines. VM is isolation of the machine while a container is isolation of the processes. It is true that when it comes to making multiple copies of containers and running multiple containers together, we need a container runtime, a piece of software that is capable of running containers.
Docker
Docker is a platform for developers to develop, ship, and run applications as portable containers. In simple words, Docker is a tool that makes it easier for developers to build, deploy, manage, and run containers. The Docker simplifies the DevOps methodology by allowing developers to create templates called images, using which one can create the lightweight virtual machine called containers.
BeforeDocker, running containers were still possible but with little hard work. Before Docker was invented, people were using Linux containers which were similar to this. Now people have adopted Docker instead of Linux containers because of its features like managing container lifecycle, monitoring the container activity, building images, setting resource limits on containers, managing proxy requests to and from the containers, and so on.
The Docker software consists of three components.
- Software: The Docker client allows users to interact with Docker. It is used to communicate with one or more daemon.
- Objects: Docker object provide an environment to run applications. The main classes of Docker objects are Docker daemon, Containers and Images.
- Registries: The Docker registry is a collection of repositories that host all docker images.
Some of the tools commonly used with the Docker include the following.
- Docker Compose: It is used for defining and running a multi-container docker application
- Docker Swarm: Provides native clustering functionality for the docker containers, which turns into a single virtual docker engine.
- Docker Volume: if you copy or create a file in a container, and when you stop that container, that file will be deleted. Docker volume addresses this issue.
Many enterprise applications involve a huge number of containers which becomes overwhelming for IT teams to manage, and this is where Kubernetes comes into the picture.
Kubernetes
Kubernetes is an open-source container orchestration system for automating computer application deployment, scaling, and management. Being the orchestration platform, it automates and increases the efficiency of containers in use. Designed by Google, Kubernetes is a highly flexible tool to deliver complex applications consistently.
Multiple container architecture is called “clusters”. Kubernetes assist the software by orchestrating a cluster of virtual machines and scheduling containers based on the available computing resource. Kubernetes architecture is a cluster that is designed as a master node and schedules efficient workloads for the rest of the parallel containers. All the other containers which are being used are termed worker nodes of the cluster.
Kubernetes can add the computing features to containers as follows
- Auto scalable infrastructure: Auto scaling is a feature in which the cluster is capable of increasing the nodes as the demand for service responses increases and decreases the number of nodes as the requirement decreases.
- Automatic rollouts & rollback: Whenever there is an update to your application, Kubernetes progressively rolls out these changes and updates to the application or its configurations.
- Self-healing capabilities: Kubernetes ensures that the actual state of the cluster and the desired state of the cluster are always in-sync.
- Load-balancing: Load balancer service is the standard solution if you want to expose your application onto the internet for effectively distributing the traffic.
- Application-centric management: Raises the level of abstraction from running an OS on virtual hardware to running an application on an OS using logical resources.
Docker vs Kubernetes
As we have discussed earlier, comparing these two platforms, Docker and Kubernetes, is like comparing apples with strawberries. Both of these platforms are good for a specific task, and they will be suited for different businesses.
While developing Kubernetes, nobody has thought that one can run Docker inside Kubernetes as we have many container runtimes such as CRI-O, rktlet, containerd, Microsoft containers and so on. Realizing this problem, the Kubernetes developers eventually developed an API called Container Runtime Interface (CRI). This platform allows us to choose from different variety of container runtimes which makes the platform independent of the Docker.
We can use Kubernetes with Docker for:
- Self-healing
- More robust infrastructure
- High availability of App
- Scalability
- Load balancing
Conclusion
It is clearthat Docker and Kubernetes are not an alternative to each other, but rather they go hand in hand.So, we can run Kubernetes without Docker and Docker without Kubernetes, but they complement each other perfectly.
Docker is a container technologythat can create an isolated environment for applications, while Kubernetes is an infrastructure for managing multiple containers. So Docker is a container platform for configuring, building, and distributing containers, while Kubernetes is an ecosystem for managing a cluster of Docker containers.
