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Introduction to Kubernetes

Kubernetes is a portable, extensible Open-Source platform for managing containerized workloads and services, that facilitates both declarative configuration and automation. It has a large, rapidly growing ecosystem. Kubernetes services, support, and tools are widely available.

Kubernetes logo

Kubernetes was first built by Google based on their experience with Borg, their in-house container-management system and Open-Sourced it in 2014. It is now maintained by the Cloud Native Computing Foundation (CNCF), which is part of the Linux Foundation. Many companies contribute to Kubernetes, including Google, RedHat, CoreOS, IBM, Microsoft, Mesosphere, VMWare, HP, and the list goes on.

With such a huge community backing it, what can Kubernetes do?

It can deploy containerized applications painlessly, automate container deployment and replication, and group containers together to provide load-balancing. It allows declaring a target architecture, deploying rolling updates, separating the application from the underlying architecture, and detecting incidents and self-healing.

Here is some Kubernetes vocabulary:

  • Pods are a small group of containers that are deployed together. This is the basic unit of all Kubernetes deployments. If a pod contains multiple containers, these will always be deployed on the same Kubernetes server and will always have the same cardinality.
  • Services are a network abstraction of pod replicas. When you have multiple instances of your application, and therefore multiple pods, connecting to the corresponding service will redirect you to any of those pods. This is how load-balancing works in Kubernetes.
  • Namespaces are a logical separation of Kubernetes components. For instance, you may have a namespace for each developer, or different namespaces for applications running in production.
  • Persistent Volume Claims (PVC) are how a pod can keep using the same persistent storage space throughout its lifecycle. If a pod is deleted and then recreated — due to a version upgrade for example — it can use its old data as long as it uses the same persistent volume claim.