Introduction to Containers – Docker and Kubernetes

Container technologies such as for example Docker and Kubernetes are necessary in modern cloud infrastructure, but what’re they and how can they work? This article will present a fast introduction to the main element concepts. To help you further understand the concepts in an even more practical manner, the introduction will be followed by way of a tutorial in creating an area development copy of Kubernetes. We will likely then deploy a MySQL database and the Joget application platform to provide a ready environment for visual, rapid application development.

Containers

Containers really are a means of packaging software in order that application code, libraries and dependencies are packed together in a repeatable way.

Now you may be asking what sort of container is different from an electronic machine (VM) running on a VM platform (called hypervisors) such as for example VMware or VirtualBox. Virtual machines include the whole operating system running on virtual hardware and will work for isolating the whole environment. For instance, you may run a complete Windows Server installation together with a Mac computer running macOS. Containers, on another hand, sit above the OS and can share libraries so they are more lightweight and thus tend to be more suitable for deployment on a larger, more efficient scale. The diagram below illustrates the difference in a visual manner for easier understanding.

Docker

Docker is definitely an open source tool to generate, deploy and run containers. In Docker and Kubernetes, you essentially define a Dockerfile that’s such as a snapshot of a software which can be deployed and run wherever a Docker runtime can be obtained, whether in the cloud, on your own PC, as well as in just a VM. Docker also supports repositories such as for example Docker Hub where container images are stored to be distributed.

While Docker is not the only real container technology available (with alternatives such as for example CoreOS rkt, Mesos, LXC), it is dominant and the de facto standard in industry right now.

Kubernetes

If Kubernetes sounds Greek for you, it’s as it literally is. Kubernetes could be the Greek word for “captain” or “helmsman of a ship, shortened to K8s (convert the center eight letters into the quantity 8), is definitely an open source container orchestration platform. What does orchestration mean in cases like this? While containers allow it to be better to package software, it generally does not aid in many operational areas, like:

  • How will you deploy containers across different machines? What happens when a machine fails?
  • How will you manage load? Just how can containers be automatically started or stopped according to the load on the machine?
  • How will you handle persistent storage? Where do containers store and share files?
  • How will you cope with failures? What happens when a container crashes?

An orchestration platform helps to manage containers in these areas, and more.

Originally developed by Google based on their need to aid massive scale, Kubernetes is now under the purview of Cloud Native Computing Foundation (CNCF), a vendor-neutral foundation managing popular open source projects.

You will find alternatives to Kubernetes (such as Docker Swarm, Mesos, Nomad, etc) but Kubernetes has seemingly won the container orchestration war having been adopted by nearly all the big vendors including Google, Amazon, Microsoft, IBM, Oracle, Red Hat and many more.

Get Started with Kubernetes

Up to now you have discovered that Docker and Kubernetes are complementary technologies. You package your applications into Docker containers, and these containers are managed by Kubernetes.

Using Docker is pretty straightforward. You basically need to put in the Docker environment, after which you will have the ability to launch container images using a “docker run” command.

Understanding and installing Kubernetes is a harder proposition. There are several basic and essential concepts that need to be understood:

  • A Kubernetes cluster includes a number of nodes. Nodes are machines that run the applications.
  • A Pod is the smallest Kubernetes object that contains a number of containers, storage resources, network IP and other configuration.
  • A Service defines a set of Pods and how they are accessed.
  • A Volume is a shared storage for containers.
  • These Kubernetes objects are defined in YAML format in .yaml files
  • A command line interface tool, kubectl, is employed to manage these objects via the Kubernetes API.

There are lots of more concepts in Kubernetes, but the essential ones above should suffice to get started with Kubernetes.

There are lots of Kubernetes solutions available for different requirements from different providers, ranging from community tools for local testing, to production environments from cloud providers and enterprise vendors.

For the objective use Minikube, an instrument that runs a single-node Kubernetes cluster in an electronic machine for local development and testing. We’ll be using a Mac running macOS, but you can adapt the instructions for the OS.

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