Architecture of Kubernetes and few lines for each component and What is POD, write a 10 lines explaination on POD by Sandhya

• Kubectl - manifest file (JSON/yaml) input on the required cluster requirement

*Master Node *

• apiserver - Front end for master node,
  - Takes manifest file for input, Updates etcds, informs scheduler on new pod requirements and so on

• Cluster store - Persistent storage for cluster state info (etcd)

• kube-controller manager - Controller of Controllers , Manages the various nodes in cluster.

• kube-scheduler - Watches apiserver for new pods and schedule them as per the requirement or availability

• kube-proxy - Takes care of Cluster networking
  - Updated the ip tables about the ports numbers and the port mapping of the pods after assigning them.

worker nodes

• kubelet - main kubernetes agent in worker node
  - instantiates pods in the node and report back to master
  - Register the node with the cluster by informing the apiserver

• Container engine - Manages containers in the node

*Pod *

• Process in node which comprises of 1 or many containers.

• Pod state will directly depend on state of containers running in it.

• Pods can be instantiated as its a process.

• Redeployment not possible. Once a pod is deleted, its gone but a similar one can be cretaed.

• instantiated by kubelet

• Pod state -> pending -> running -> succeeds/fails based on container state

• Interpod communiation - Pod network

• Intra pod container - local host