ETCD

1. Etcd is a distributed reliable key-value store that is simple, secure, and fast.
2. Key-value store (document DB, jasn-yaml-like structure)
   • set a key value pair in etcd:

   1	etcdctl set key value

3. Every info (eg. Nodes, pods, configs, secrets) are stored in ETCD cluster.
4. k8s stored structure:
   

Kube-API server

1. how get node work?

2. how create pod work?

Kube controller Manager

1. Continueously watch the status.
2. take necessary action to remediate the situation.

remediate: to correct something that is wrong or damaged or to improve a bad situation.