Kubernetes – Objects – simplifying concepts

kubernetes - list of objects
kubernetes - list of objects

Hi All,

GREETINGS FOR THE DAY 🙂 LIFE IS BEAUTIFUL 🙂

We are discussing Kubernetes. In previous few articles we discussed

Today in this article we will discuss about – Kubernetes objects. We discussed about Kubernetes – POD which is one of the Kubernetes object

Take away from this article

  • What are Kubernetes objects
  • How to get list of Kubernetes objects
  • How to create Kubernetes objects

What are Kubernetes objects

  • Kubernetes objects which are the entities and integral part of Kubernetes cluster
  • We can say that Kubernetes objects are building blocks of Kubernetes cluster
  • Kubernetes objects are used to
    • To deploy our containerised applications (docker images)
    • On which node in Kubernetes cluster containerised applications are running
    • To maintain the healthy state of Kubernetes cluster
    • To make sure our containerised applications are working in healthy state

There are lots of Kubernetes object. We can get list of all kubernetes objects by executing the command

 kubectl api-resources

Output of the above CMDLET will be

Kubernetes - list of objects
fig : Kubernetes – list of objects
Kubernetes - list of objects
fig : Kubernetes – list of objects

Following are some/popular Kubernetes objects – Here I am adding just short description for each object and then we will have detailed article for each object like we have separate detailed article for POD

  • Namespaces
    • Namespaces come into the picture when we want to share single cluster with multiple users / teams
    • Namespaces provides us scope for names
    • Kubernetes comes with three default namespaces:
      • default The default namespace for objects having no namespaces
      • kube-system The namespace for objects created by the Kubernetes system
      • kube-public This namespace is created automatically and is readable by all users (including those not authenticated)
  • PODs
    • Kubernetes system dosent understand our containerised application, Kubernetes understand PODs, those are wrapper for our containerized application in Kubernetes
    • In nutshell, POD contains one more containers
    • We have separate detailed article on PODs – https://knowledge-junction.com/2022/05/05/kubernetes-pod/
  • Replication Controller
    • Allows us to have multiple instances of single pod in Kubernetes cluster
    • Replication controller helps new pod instance in case existing pod fails
    • Itss make sure that at any given time specified number of Pods are running
  • Replica Sets
    • Replica sets are the new way to maintain the replicas
    • Replica sets are replacement of Replication Controller
    • Replica set and Replication controller provide same set of functionality but replica set is more powerful
  • Deployments
    • Object which represents our running application on cluster
    • Deployments are used to manages pods in Kubernetes cluster
    • Deployment object creates replica sets and number of pods as specified the value of replicas
  • Services
    • Service object is logical set of Pod objects
    • Service object have unchanged ip address
    • Service object specifies how to access the respective Pods
    • Service object helps to connect in between applications, like if our application connects any external data source
    • It allows the connectivity between frontend and backend group of pods
    • Default protocol for services is TCP
  • Ingress
    • Objects which allows access to Kubernetes services from outside the kubernetes cluster
    • This access is allowed via HTTP / HTTPs
  • Volumes
    • Persistent storage used by Kubernetes to store the data stored in containers
    • Data is preserved across container restarts
    • Volume is a directory, possibly with some data in it, which is accessible to the containers in a pod
  • ConfigMaps
    • Used to store non-confidential data in key value pair
    • ConfigMap does not provide secrecy or encryption
    • Used to store data separately from our application code
  • Secrets
    • Used to store confidential data
    • Basically small amount of data like Password / Token or keys

How the Kubernetes objects are created

  • Kubernetes objects can be created , modified or deleted with the help of Kubernetes APIs
  • Mostly we / administrators uses kubectl command line utility tool
  • Every object in Kubernetes have specification which tells Kubernetes system – the desired state of object
  • Most of the time Kubernetes object specification is yaml file – to know more details about yaml files, please have a look of our detailed article – https://knowledge-junction.com/2021/09/04/complete-guide-to-yaml/

Thanks for reading the article !!! Please feel free to discuss in case any issues / suggestions / thoughts / questions !!!

HAVE A GREAT TIME AHEAD !!!

Prasham Sabadra

LIFE IS VERY BEAUTIFUL :) ENJOY THE WHOLE JOURNEY :) Founder of Knowledge Junction and live-beautiful-life.com, Author, Learner, Passionate Techie, avid reader. Certified Professional Workshop Facilitator / Public Speaker. Scrum Foundation Professional certificated. Motivational, Behavioral , Technical speaker. Speaks in various events including SharePoint Saturdays, Boot camps, Collages / Schools, local chapter. Can reach me for Microsoft 365, Azure, DevOps, SharePoint, Teams, Power Platform, JavaScript.

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