DevOps Classroomnotes 23/Apr/2023

Kubernetes Objects

• Every thing in k8s is an object.
• Every object has a spec and status
• spec: specification (what we have asked)
• status: (what was created)

Kuberenetes API-Resources

• The resources exposed by api-server
  

K8s Workloads

• Refer Here for the official docs
  
• Pods:
• Primitive of k8s.
• The smallest unit of creation is Pod.
• Pod has container(s)
• Every Pod gets an IP address

How to Create Resources in K8s

• We would be creating k8s manifests i.e yaml files
• For this we need to understand
  • yaml
  • api versioning
  • Spec and Status

API Versioning

• Refer Here for docs
• APIs are grouped as apigroups:
  • core
  • batch
  • networking.k8s.io
• Api version: This is written as <groupname>/<Version>, if the group name is core <version>
• In this groups we have kind of api-resources

Defining Resources in a manifest file

• To define a resource in a manifest file we create a yaml file with following structure

apiVersion: 
kind:
metadata:
spec:

• Open the api reference Refer Here

Pods

• Pod is atomic unit of creation in k8s cluster
• Pod contains container(s)
  
• Each Pod gets a unique ip address
• Pod can have multiple containers
• Scaling in k8s is increasing number of pods not containers
  
• Pod gets assigned to node
• Refer Here for official docs
• Refer Here for podspecs
• kubectl cheatsheet Refer Here
• using kubectl to create pods
  
• commands

kubectl apply -f
kubectl get <api-resource>
kubectl describe <kind> <name>

* To view the complete manifest created by k8s

kubectl get <kind> <name> -o yaml

• delete pods
  

Exercises

• Write a manifest file to create
  • nginx
    
  • nginx and alpine with sleep 1d
    
  • nginx ,alpine with sleep 1d and alpine with 10s
    
  • nginx and httpd with 80 port exposed
    
• Refer Here for the changeset with 4 yamls