Home / Cheatsheets / Kubernetes

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Contents

• Basic Objects
• Service Types
• Controllers
• Control Plane

Basic Objects

• pod - container / set of containers + storage resources + unique IP + local options

• service - abstraction layer on top of a set of ephemeral pods (think of this as the ‘face’ of a set of pods)

• volume - sometimes-shared, persistent storage

• namespace - virtual cluster on top of an underlying physical cluster

Service Types

• clusterIP - exposes services only inside the cluster (default)

• nodePort - exposes services at the specified port on all nodes (:)

• loadBalancer - exposes the service with a cloud-provider’s load balancer.

• externalName - this maps a service to endpoints completely outside of the cluster

Controllers

• replicaSet - ensures a certain number of pods are running

• deployment - declaratively manages a replicaSet

• statefulSet - like a deployment, but for non-interchangeable (or stateful) underlying pods

• daemonSet - manages pods that need to run on all/some nodes

• job - manages a set of pods that run to completion and tracks the overall progress

Control Plane

• master - entity responsible for managing cluster state. It consists of 3 major components:

  • kube-apiserver - exposes cluster control and state

  • kube-controller-manager - this is where the ‘brain’ of controllers live

  • kube-scheduler - matches resources to work

• node - individual machines or VMs that make up the cluster. A node consists of:

  • kubelet - service that communicates with the master

  • kube-proxy - proxy for connecting to the cluster network

namespace -> virtual cluster on top of an underlying physical cluster

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