---
id: mat-01-kubernetes-primer
title: "Kubernetes Primer"
---

# Kubernetes primer

## Kubernetes background
Kubernetes is an application orchestrator that helps you:
- deploy applications
- scale them up/down based on demand
- self-heal when things break
- do rolling updates and rollbacks
- and more

## Cloud-native and microservice apps
A cloud-native app typically demands:
- auto-scaling
- self-healing
- rolling updates
- rollbacks

A microservices app typically demands:
- lots of small, specialized, independent parts that work together
- e.g., front-end, back-end, database, many services in a mesh

## Where Kubernetes comes from
- Early public cloud era: AWS popularized modern cloud computing
- Google already ran large containerized apps (e.g., Search/Gmail) and developed in-house orchestration systems (Borg, Omega)
- Kubernetes was created from those lessons and donated to the CNCF in 2014 as an open-source project

## Kubernetes and Docker (historical view)
At first:
- Docker build tools packaged apps as containers
- Kubernetes made scheduling/orchestration decisions
- Docker runtime was installed on each worker node

Now:
- Kubernetes uses a container runtime layer via CRI (Container Runtime Interface)

## What’s in the name (K8s)
- “Kubernetes” is often shortened to “K8s” (“kates”)
- “Kubernetes” comes from Greek meaning “helmsman” (the person who steers a ship)

## Kubernetes from 40K feet (cluster view)
A Kubernetes cluster runs applications on:
- control plane nodes
- worker nodes

## Control plane
The control plane is a collection of services that control and run everything.
Common services:
- API Server
- cluster store (etcd)
- controller manager (reconciles desired vs current state)
- scheduler

## Worker nodes
Worker nodes are where user applications run.
Worker node work logic:
- watch the API server for work assignments
- execute work assignments
- report back to the API server

### Worker node components
- kubelet: main agent on every worker, executes tasks and reports
- container runtime: pulls images, starts/stops containers (via CRI; e.g., containerd)
- kube-proxy: local networking (routing, iptables, load balancing)