Do you suffer from Impostor Syndrome when you come across the words Docker and Kubernetes on a Saturday night get-to-together or at a workplace?! Well, it definitely is no rocket science. Before I start anything, it is never an Either/Or question. Docker is like an aeroplane and Kubernetes is like an airport. You wouldn’t ask “Which one should I use to travel?” So it goes without saying that you need both Docker and Kubernetes.
In this blog post, I will give an overview of how does Kubernetes work with Docker. By the end of the blog, there will a clear picture with all the small pieces of puzzles coming together. The topics covered are as follows:
- What is Docker?
- How Does Docker Work?
- What is Kubernetes?
- How Does Kubernetes Work?
- How Does Kubernetes Work with Docker?
- Application Deployment using Kubernetes and Docker
What is Docker?
Docker is mainly a software development platform, and kind of a virtualization technology that makes it easy for us to develop and deploy applications inside neatly packaged virtual containerized environments. Docker containers can be deployed to just about any machine without any compatibility issues so the software stays system-agnostic i.e. the applications are OS independent. Also, it makes the application simpler to use with less work to develop and easier to maintain and deploy.
How Does Docker Work?
Docker Workflow
Before we hop on to the working of Docker, let us look into the general workflow of Docker. A developer defines all the necessary dependencies and requirements of an application in a file called a Dockerfile. The Dockerfile is used to create a Docker Image which is nothing but a template, if we run the same a Docker Container is created. A Docker Container is nothing but a runtime instance of a Docker Image and these images can also be stored in an online cloud repository called the Docker Hub. You can pull the images from the Docker Hub and start deploying and running your applications on any environment.
Container/Docker Architecture
Docker resolves the compatibility matrix issue referred to as ‘The Matrix from Hell!‘ The containerization of Docker has an infrastructure and an Operating System on top of it but it doesn’t have a Hypervisor like in Virtualization. It has a process that runs directly on the OS knowns as Docker Daemon, this is what facilitates and manages the running containers on the system, the Docker Images and all of the Docker Commands as well. The applications that you run within the images basically run directly on the host machine. This running instance of an image is called a Docker Container. Hence, the main purpose of Docker is to package and containerize applications and to ship them and run them anywhere any number of times.
Docker is OS independent and can run on all platforms. Uses very less resources comparably to the VMs. Since the size of the Docker container is in MBs they always boot up swiftly! Therefore Docker is well ahead of the Virtual Machines, have a quick look at how Docker wins the challenge of Docker vs Virtual Machines.
What is Kubernetes?
Kubernetes is an open-source orchestration tool that allows you to run and manage your container-based workloads. Kubernetes a.ka. K8s was Developed by google and was later donated to the Cloud Native Computing Foundation. Kubernetes helps you manage hundreds and thousands of containerized applications in different deployable environments be it physical machines, virtual machines, cloud or even hybrid environments!
In simple words, it’s a container orchestrator that helps makes sure that each container is where it’s supposed to be and that the container can work together. To put it another way, it is pretty similar to a conductor that manages everything in an orchestra. Since there are a lot of moving points in the scalable application, the same way how a conductor is responsible for making the song sound good similarly K8s makes sure the services smoothly the way an app developer wants.
How Does Kubernetes Work?
Kubernetes was made to solve the problems of the Monolith approach of application deployment used to face. This is where the Microservice type of approach comes into the picture. To get to know why Microservice is the business as of today, have a look at Monolithic vs Microservices. Kubernetes and the Microservice approach has made the lives of so many tech-giants easier!
Kubernetes Architecture
A working Kubernetes deployment is called a Kubernetes Cluster. You can visualize a Kubernetes cluster as two parts: the control plane/master node and the compute machines or the worker nodes. Each node is its own Linux environment and could be either a physical or virtual machine. Each node runs pods, which are made up of containers.
The architecture of Kubernetes consists of Master nodes and Worker nodes as mentioned earlier, and the Master communicates with the Worker using API-server. Multiple Master nodes may also exist in order to provide High Availability, which is indeed one of the most important aspects of application deployment and also an advantage of Kubernetes.
Read More: Here is a good read on Kubernetes Architecture: An Introduction to Kubernetes Components
How Does Kubernetes Work with Docker?
You’d have figured it by now that Docker helps to “create” containers whereas K8s enables you to “manage” them at runtime. Docker is used in packing and hip your application. In the same way, K8s empowers you to deploy and scale your application. Kubernetes comes into the picture only when there are more containers that need to be managed. While the big tech-giants are in h race to adapt to Kubernetes, small startups preferably wouldn’t be needing K8s for managing their applications. But, as the companies grow, their infrastructure needs will rise; hence, the number of containers will increase, which can be difficult to manage. Voila! this is where Kubernetes comes in.
When used together, Docker and K8s serve as digital transformation enablers and tools for modern cloud architecture. Using both has become a new norm in the industry for faster application deployments and releases. As mentioned above, it’s not enough to merely run containers in production, they need to be regulated and Kubernetes offers some great features that make working with containers a lot facile. K8s provides us with auto-scaling, health checks, and load balancing which are crucial to managing the container lifecycle. Kubernetes constantly checks the state of deployment according to the yaml definition. Accordingly, if a Docker container goes down, K8s will spin up a new one automatically.
To summarize, Docker containers will help you to isolate and pack your software with all its dependencies. Kubernetes on the other hand will help you to deploy and orchestrate your containers. The takeaway point is that when you combine Docker and Kubernetes, confidence and productivity increase for everyone.
Application Deployment using Kubernetes and Docker
You need a container runtime like Docker Engine to start and stop containers on a host. When you have a bunch of containers running across a bunch of hosts, you need an orchestrator to manage things like: Where will the next container start? How do you make a container highly available? How do you control which containers can communicate with other containers? That’s where an orchestrator such as Kubernetes comes into play.
Comparing traditional, virtualized, containerized and Kubernetes deployment architectures (Credits: docker.com)
There are a few steps to be followed to deploy a Docker Image to a Kubernetes Cluster. The whole process might seem a bit intimidating if you are pretty new to Kubernetes and Docker but with preparation, it’s just effortless. The steps involved in a deployment depends on the type of application that you are going to deploy. Down below I will list the steps involved in deploying a web application:
- Package a sample web application into a Docker image.
- Upload the Docker image to Container Registry.
- Create a Kubernetes cluster.
- Deploy the sample app to the cluster.
- Manage autoscaling for the deployment.
- Expose the sample app to the internet.
- Deploy a new version of the sample app.
Related Post
- Kubernetes for Beginners
- Kubernetes Architecture | An Introduction to Kubernetes Components
- Docker Architecture, Docker Engine Components, Container Lifecycle
- Docker Images: A Complete Guide For Beginners
- Kubernetes vs Docker – Understand the Difference-and-docker
- Install Docker on Windows, Ubuntu and Mac: A Complete Step-by-Step Guide
- Container (Docker) vs Virtual Machines (VM): What Is The Difference?
- How To Setup A Three Node Kubernetes Cluster For CKA: Step By Step
- Visit our YouTube channel on “Docker & Kubernetes”
- Certified Kubernetes Administrator (CKA) Certification Exam: Everything You Must Know
- Certified Kubernetes Administrator (CKA) Certification: Step By Step Activity Guides/Hands-On Lab Exercise
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