chan18/kubernetes

Kubernetes Practice

master nodes ( controle plane ) worker nodes ( minions )

Cloud : ( kubernetes service ) - cloud provider handls the master node.

EKS GKS AKS

Control Plane

Desired State : EG: 3 containers running any point of time, is a typical desired state

Control Plane flow:

When a users request a desired state :

1. User ( desired state ) -> REST API -> database ( ETCD )
2. Kube-controller-manger -> Rest API ( controller manager does keep triggers the API for new updates )
   • Kube controller manger will have following controllers in it eg; Scheduler controller
3. Worker nodes runs some workloads
   • Worker nodes uses some sort of run time eg : docker, CIR-0, container-d are the container runtimes.
   • Kubelet responsible for communicating to control plane.
     • If any scheduled containers, kubelet will trigger container run time to run bunch of containers
   • Kube-proxy responsible for communication inside the cluster.
4. K8’s building blocks
   • The pod : pod is a smallest unit we can work with in kubernets
     • A POD contains one or more containers.
     • If multiple containers running in a single pod all of them will have same ip address with different ports.they can communicate between each adjacent containers also share storage
     • We can schedule multiple pods in kuberenetes cluster.

Kubectl

Generic syntax : Kubectl < get , delete , create > < resource type >

List pods: Kubectl get pods

List specific pod: Kubectl get pod my-pod

Create : Kubectl < create, apply > -f ./my-pod-config.yml

Port forwarding: Kubectl port-forward my-pod 8080:80

Creating pods :

Kubectl run —generator=run-pod/v1 webapp –image=k8s4devs.azurecr.io/k8sdevs/webapp:v0.2