Kubernetes Classroom 12/Oct/2019 – API, Objects & Versions

Operation modes of kubectl


  • I would tell kubectl what action has to be taken
kubectl run tomcat --image=tomcat:8


  • Maintaining declared state.
  • Declarative state is mentioned in some file.
  • To describe Declarative State in k8s we use YAML files.
  • Lets assume you have yaml file test.yml.
kubctl apply -f test.yml
kubectl delete -f test.yml

Kubernetes APIs

  • All capabilities of K8s are exposed as REST APIs
  • To execute APIs
    • kubectl
    • Client Libraries
  • APIs are changing every day, then how should i use in my Production Systems.

API Versions

  • Are of three types
    • Alpha: inside api version if you see alpha
    • Beta: inside api version if you see beta
    • Stable: inside api version if you see vX here X is a integer

API groups

Refer here for more info

Resources and Objects

  • Resources are all the possibilities in K8s
  • Objects are what you are creating


kubectl api-versions

Resource Category Workload

  • Pod:

    • smallest unit of creation in k8s
    • Pod has
      • Container(s)
      • Storage
      • IP Address
  • Controller

Kubernetes Objects

  • Object has two nested groups
    • Object Spec:

      • input
      • Desired state
    • Object Status:

      • output
      • Actual State
  • Syntax:
apiVersion: <apiversion>
kind: <type>
    key1: <value1>
spec: <objectspec>

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