Kubernetes cluster concepts

Category : Kubernetes | Sub Category : Kubernetes With Java | By Prasad Bonam Last updated: 2023-11-21 10:50:34 Viewed : 401

A Kubernetes cluster is a set of physical or virtual machines (nodes) that run containerized applications orchestrated by Kubernetes. Here are some key concepts related to Kubernetes clusters:

1. Nodes:

  • Nodes are the individual machines (physical or virtual) in the cluster where containers are deployed.
  • Each node runs a container runtime (like Docker) and has the necessary Kubernetes components (kubelet and kube-proxy) to communicate with the master.

2. Master:

  • The master node is responsible for managing the overall state of the cluster.
  • It schedules applications, maintains the desired state, and monitors and responds to node and pod failures.
  • Components include the API server, controller manager, scheduler, and etcd.

3. Control Plane:

  • The control plane is a set of components on the master node that collectively manages the cluster.
  • Key components: API Server, etcd, Controller Manager, and Scheduler.

4. Pod:

  • The smallest deployable units in Kubernetes.
  • A pod represents a single instance of a running process in a cluster.
  • A pod can contain one or more containers that are tightly coupled and share the same network namespace, storage, and specifications.

5. Namespace:

  • A way to divide cluster resources between multiple users or projects.
  • Namespaces provide a scope for names, making it easier to organize and isolate resources within a cluster.

6. Service:

  • An abstraction that defines a logical set of pods and a policy by which to access them.
  • Services enable communication between different parts of an application, or between applications.

7. ReplicaSet:

  • Ensures that a specified number of replicas (instances) of a pod are running at all times.
  • Provides scaling and high availability for pods.

8. Deployment:

  • Manages the deployment and scaling of a set of pods.
  • Provides declarative updates to applications, allowing you to describe the desired state for your deployed containers.

9. ConfigMap and Secret:

  • ConfigMap holds configuration data as key-value pairs.
  • Secret holds sensitive information, such as passwords or API keys.

10. Kubelet:

  • The primary "node agent" that runs on each node.
  • Ensures that containers are running in a Pod.

11. Kube Proxy:

  • Maintains network rules on nodes.
  • Enables communication to Pods from network sessions inside or outside the cluster.

12. StorageClass and PersistentVolume:

  • StorageClass defines different classes of storage.
  • PersistentVolume represents a piece of storage in the cluster.

13. Ingress:

  • Manages external access to services within a cluster.
  • Provides HTTP and HTTPS routing to services based on rules.

14. RBAC (Role-Based Access Control):

  • Defines what actions are allowed or denied for different users or systems within a cluster.

15. ClusterRole and ClusterRoleBinding:

  • Similar to RBAC but applies at the cluster level.

Understanding these concepts is crucial for effectively deploying, managing, and scaling applications in a Kubernetes cluster. The architecture and flexibility of Kubernetes provide a robust platform for container orchestration and application management.

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