[Kubernetes] Kubernetes concepts

source : The Gruntwork Blog

 

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. Here’s a breakdown of core concepts and main components:

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🔹 Core Concepts

source : Kubernetes

1. Cluster
   A set of machines (nodes) running Kubernetes. It consists of a control plane and worker nodes.
2. Node
   A physical or virtual machine in the cluster that runs pods. There are:
   • Master/Control Plane node (manages the cluster)
   • Worker node (runs the application workloads)
3. Pod
   The smallest deployable unit in Kubernetes. A pod contains one or more containers with shared storage, network, and specifications.
4. Container
   A lightweight, standalone, executable software package that includes everything needed to run a piece of software.
5. Service
   An abstraction that defines a logical set of pods and a policy to access them—usually to enable network access across pods.
6. Deployment
   A controller that manages pod replicas and ensures the desired number of them are running at all times.
7. Namespace
   A way to divide cluster resources between multiple users or teams (useful for multi-tenancy).

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🔧 Main Components

Kubernetes consists of two main nodes: Master & Worker.

Master node manages, plans, schedules, and monitors nodes.

Worker nodes host application as containers.

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🚀 Control Plane Components

These manage the Kubernetes cluster.

• kube-apiserver
  The front end of the Kubernetes control plane. It exposes the Kubernetes API.
• etcd
  A distributed key-value store used for storing all cluster data.
• kube-scheduler
  Assigns pods to nodes based on resource availability and policies.
• kube-controller-manager
  Runs controller processes (e.g., replication controller, node controller, etc.) to handle routine tasks.
• cloud-controller-manager (optional)
  Manages cloud-specific control logic (e.g., load balancers, volume storage, etc.).

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⚙️ Node Components

• kubelet
  An agent that runs on each worker node and ensures containers are running in a pod.
• kube-proxy
  Maintains network rules on nodes and handles network traffic to and from pods.
• Container Runtime
  The software used to run containers (e.g., Docker, containerd, CRI-O).

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참고 자료

 - Kubernetes Node Vs. Pod Vs. Cluster: Key Differences

 

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