Explain POD in Kubernetes

POD

➢ Smallest unit in Kubernetes.
➢ POD is a group of one or more containers that are deployed together on the same host. ➢ A cluster is a group of nodes.
➢ A cluster has at least one worker node and master node.
➢ In Kubernetes the control unit is the POD, not containers.
➢ It consists of one or more tightly coupled containers.
➢ POD runs on node which is control by master.
➢ Kubernetes only knows about PODs (does not know about individual container).
➢ Cannot start containers without a POD.
➢ One POD usually contains one container.

Multi container PODs:

➢ Share access to memory space.
➢ Connect to each other using local host <container port>.
➢ Share access to the same volume.
➢ Containers within POD are deployed in an all-or-nothing manner.
➢ Entire POD is hosted on the same node (scheduler will decide about which node).

POD limitations:

➢ No auto healing or auto scaling.

➢ POD crashes.

Higher level Kubernetes objects:

• Replication set: auto scaling and auto healing
• Deployment: versioning and rollback
• Service:
• Static (non-ephemeral) IP and networking.
• Volume: non-ephemeral storage.

Important:

Kubectl- single cloud

Kubeadm- on premise

Kubefed- federated