Key components: Master, Node, Pods, Services.

Category : Kubernetes | Sub Category : Learn Kubernetes | By Prasad Bonam Last updated: 2023-11-22 07:12:19 Viewed : 549

Key components: Master, Node, Pods, Services.

lets delve into the key components of Kubernetes: Master, Node, Pods, and Services.

1. Master:

   • The master node is the control plane of the Kubernetes cluster. It manages the overall state and orchestration of the cluster.

   • Components:

     • API Server: Exposes the Kubernetes API. It is the front end of the control plane and the only component that interacts with the etcd cluster to persist the state of the cluster.
     • Controller Manager: Ensures the desired state of the cluster by running controller processes (e.g., ReplicaSet Controller, Endpoint Controller).
     • Scheduler: Assigns pods to nodes based on resource requirements and constraints.

   • Example:

     • Deploying a pod using the kubectl command involves interacting with the API server. For example:

       bashCopy code
       kubectl create deployment my-deployment --image=my-image
       

2. Node (Minion):

   • A node is a worker machine in Kubernetes, responsible for running containers and providing the runtime environment.

   • Components:

     • Kubelet: Ensures that containers are running in a pod on the node.
     • Container Runtime: Software responsible for running containers (e.g., Docker, containerd).
     • Kube Proxy: Maintains network rules on the host and enables communication between pods.

   • Example:

     • Deploying a pod to a node involves the Kubelet interacting with the container runtime. For example:

       yamlCopy code
       apiVersion: v1
       kind: Pod
       metadata:
         name: my-pod
       spec:
         containers:
         - name: my-container
           image: my-image
       

3. Pods:

   • The smallest and simplest unit in the Kubernetes object model. A pod represents a single instance of a running process in a cluster.

   • Characteristics:

     • Pods can have one or more containers sharing the same network namespace.
     • Containers in a pod share storage volumes.
     • Pods are the basic deployable units in Kubernetes.

   • Example:

     • Defining a pod with two containers:

       yamlCopy code
       apiVersion: v1
       kind: Pod
       metadata:
         name: my-pod
       spec:
         containers:
         - name: container-1
           image: image-1
         - name: container-2
           image: image-2
       

4. Services:

   • Services define a set of pods and a policy by which to access them, providing a stable endpoint for communication.

   • Types:

     • ClusterIP: Exposes the service on an internal IP within the cluster.
     • NodePort: Exposes the service on a static port on each nodes IP.
     • LoadBalancer: Creates an external load balancer and assigns a unique external IP.

   • Example:

     • Creating a service to expose a set of pods:

       yamlCopy code
       apiVersion: v1
       kind: Service
       metadata:
         name: my-service
       spec:
         selector:
           app: my-app
         ports:
           - protocol: TCP
             port: 80
             targetPort: 8080
       

Understanding these key components is fundamental to working effectively with Kubernetes. The master controls the cluster, nodes run containers, pods encapsulate containers, and services enable communication between pods.