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┌────────────────────────────────────────────────────────────────────────────────┐
│ ┌──────────┐ │
│ ┌───────────│Container │ │
│ │ └──────────┘ │
│ ┌───────────────────────────┼────────────┐ │
│ │ Deployment ┌────────┼─────┐ │ │
│ │ │ Pod ┌──┴┐ │ │ │
│ │ │ │┌──┴┐ │ │ │
│ │ ┌───────────│ └┤ │ │──┐ │ │
│┌───────┐ │ │ │ └───┘ │ │ │ │
││Service│────┼──────┤ └──────────────┘ │ │ │
│└───────┘ │ │ ┌──────────────┐ │ │ │
│ │ │ │ Pod ┌───┐ │ │ │ │
│ │ │ │ │┌──┴┐ │ │ │ │
│ │ └───────────│ └┤ │ │──┼───┼─────────────┐ │
│ │ ┌─────────┐ │ └───┘ │ │ │ │ │
│ │ │ Replica │ └────────┬─────┘ │ │ │ │
│ │ │ Set │────────────┴────────┘ │ │ │
│ │ │ │ │ ┌───────────────────┐ │
│ │ └─────────┘ │ │ Persistent Volume │ │
│ │ │ │ Claim │ │
│ └────────────────────────────────────────┘ └───────────────────┘ │
│ │ │
│ │ │
│ │ │
│ ┌───────────────────┐ │
└──────────────────────────────────────────────────────────┤ Persistent Volume ├─┘
└───────────────────┘
A pod is a group of one or more containers, with shared storage/network, and a specification for how to run the containers.
A Replica Set ensures that a specified number of pod replicas are running at any one time. In other words, a Replica Set makes sure that a pod or a homogeneous set of pods is always up and available. A Replica set help you to define how many pods are available. If you define replica as three, then one pod die, the Replica Set create a pod to make it three.
A Deployment controller provides declarative updates for Pods and ReplicaSets.You describe a desired state in a Deployment object, and the Deployment controller changes the actual state to the desired state at a controlled rate. You can define Deployments to create new ReplicaSets, or to remove existing Deployments and adopt all their resources with new Deployments. A Deployment include Pod(s) and Replica Set. It also help to update the resources when you deploy new version.
A Kubernetes Service is an abstraction which defines a logical set of Pods and a policy by which to access them - sometimes called a micro-service. If you create a pod, you don’t know where it is. Also, a pod might be killed by someone or some shortage of a node. Service provide an endpoint of the pods for you. If you specify “type=NodePort” it actually creates a port to expose pod with an IP address.
Presistent Volume Claim is the abstraction of the Persistent Volume. Persistent Volume is physical resources of infrastructure. Kubernetes want to hide the detail from developers. Using Persistent Volume Claim, you can hide the physical declaration defined by Persistent Volume. Pods can mount the Volumes using Persistent Volume Claim objects.