k8s/StudyNotes

k8s/StudyNotes/cubectl k8s/StudyNotes/Deployments

• https://kodekloud.com/

* kubeadm

• deploys all the kubernetes services downloaded from web

* Kube-Scheduler

1. Filter Nodes (Pod cant fit)
2. Rank Nodes (Compare resources left, try to balance cpu/mem usage)

• kubelet - captain on each Worker Node
  • Registers with Master node, reports status and executes

  • Always manual install wget https://storage.googleapis.com/kubernetes-release/release/v1.xx.x/bin/linux/amd64/kubelet

    • Not kubeadm managed.
    • Needs tls bootstrap
• Kube-proxy - run on each node, service's virtual component
  • All pods can see all other pods, through POD Network, by IP/Name. Exposed through service: eg. db(IP)
  • Watches for service creation, and then configure network e.g. Iptables to forward to actual pod.
  • Install: download wget to install or
    • kubeadm will deploy it as deamon set to each pod in namespace kube-system
• PODs
  • smallest object in k8s, contains containers, can contain one or more containers
  • scale service by creating more pod instances.
  • additional container could be helper container.
  • network space is shared between containers in the same pod, they can communicate on localhost.
  • k8s Controllers - the brains

    • ReplicaSets - Replication controller -> newer -> Replica Sets

      1. yml definition ReplicationController same 4 sections as other configs

         • apiVersion: v1

         • kind: ReplicationController

         • metadata:
           • name: myapp-rc labels:
             • app: myapp type: front-end
         • spec:
           • template:

             • <pod definition nested, with same 2 sections, metadata, spec>

             replicas: 3

      2. yml definition newer ReplicationSet, requires selector:

         • apiVersion: apps/v1

         • kind: ReplicaSet

         • metadata:
           • name: myapp-rc labels:
             • app: myapp type: front-end
         • spec:
           • template:

             • <pod definition nested, with same 2 sections, metadata, spec>

             replicas: 3 selector:
             • matchLabels:
               • type: front-end