Understanding Concepts

To properly utilize Kubernetes, knowing kubectl commands alone is not enough. You need to understand why you need multiple Pods, how Services distribute traffic, and where to store configurations to quickly diagnose and resolve operational issues. This section covers Kubernetes core components and operating principles step by step.

Overall Concept Structure#

The diagram below shows the relationships between Kubernetes core concepts. Arrow directions indicate dependency or reference relationships.

flowchart TB
    subgraph Cluster[Cluster Structure]
        ARCH[Architecture]
    end

    subgraph Workload[Workload]
        POD[Pod]
        DEP[Deployment]
        DEP -->|manages| POD
    end

    subgraph Network[Network]
        SVC[Service]
        NET[Networking/Ingress]
        SVC -->|exposes| POD
        NET -->|routes| SVC
    end

    subgraph Config[Configuration]
        CM[ConfigMap/Secret]
        CM -->|injects| POD
    end

    subgraph Storage[Storage]
        VOL[Volume/PV/PVC]
        VOL -->|mounts| POD
    end

    subgraph Operations[Operations]
        RES[Resource Management]
        SCALE[Scaling]
        HEALTH[Health Checks]
        RES -->|configures| POD
        SCALE -->|adjusts| DEP
        HEALTH -->|monitors| POD
    end

    ARCH -.->|composes| POD

Concept Summary#

Concept	One-line Summary	Key Question
Architecture	Cluster structure composed of Control Plane and Worker Nodes	“How does Kubernetes work?”
Pod	Minimum deployment unit wrapping containers	“Why Pod instead of container?”
Deployment	Declarative deployment and update management of Pods	“How to deploy without downtime?”
Service	Stable network access point for Pods	“How to find changing Pod IPs?”
ConfigMap/Secret	Separate management of configuration and sensitive information	“How to separate config from code?”
Volume/Storage	Data storage independent of Pod lifecycle	“How to persist data when Pod dies?”
Networking	Cluster internal/external communication and Ingress	“How to access from outside?”
Resource Management	CPU/memory requests and limits configuration	“How much resources to allocate?”
Scaling	Automatic scaling with HPA/VPA	“How to respond to traffic increases?”
Health Checks	Status monitoring and auto-recovery through Probes	“How to verify app is healthy?”
Namespace	Mechanism to logically isolate resources within a cluster	“How to separate resources by team?”
StatefulSet	Deployment and management of stateful applications	“How to deploy a DB on Kubernetes?”
RBAC	Role-based access control for API permission management	“Who can access which resources?”
Jobs and CronJobs	One-time and recurring batch job execution	“How to run batch jobs?”
NetworkPolicy	Control network traffic between Pods	“How to restrict Pod-to-Pod communication?”

Learning Path#

The learning path below is designed considering dependencies between concepts. It’s recommended to thoroughly understand basic concepts before moving to advanced topics. Pod and Deployment especially are the foundation for all subsequent concepts and should be well understood.

Basic Concepts

Basic concepts cover the core elements that compose a Kubernetes cluster and the application deployment process. The goal is to understand how Pods are created, how Deployments manage Pods, and how Services deliver traffic.

Architecture - Understand components of Control Plane and Worker Nodes. Grasp the big picture of how Kubernetes operates.
Pod - Learn the concept and lifecycle of Pod, the minimum deployment unit in Kubernetes. Understand why we use Pods instead of containers.
Deployment - Learn Deployment that manages Pod creation, updates, and rollbacks. Understand the principles of zero-downtime deployment.
Service - Learn Service that provides stable network access to Pods. Understand the differences between ClusterIP, NodePort, and LoadBalancer.
ConfigMap and Secret - Learn how to separate and manage application configuration and sensitive information.

Advanced Topics

Advanced topics cover subjects necessary for stable Kubernetes operations in production environments. This includes persistent data storage, network configuration, resource management, auto-scaling, and other content essential for actual service operations.

Volume and Storage - Learn Persistent Volumes (PV) and Persistent Volume Claims (PVC) that retain data even after Pod termination.
Networking - Learn the principles of cluster internal/external communication and HTTP routing through Ingress.
Resource Management - Learn how to configure CPU and memory requests and limits. Understand behavior under resource shortage situations.
Scaling - Learn auto-scaling through HPA (Horizontal Pod Autoscaler) and the concept of VPA.
Health Checks - Learn how to monitor application status and auto-recover through Liveness, Readiness, and Startup Probes.

Advanced Topics

Advanced topics cover multi-tenant environment setup, stateful workloads, security, batch processing, and other practical in-depth content.

Namespace - Learn how to logically isolate resources within a cluster and limit usage with ResourceQuota.
StatefulSet - Learn how to deploy and manage stateful applications like databases.
RBAC - Learn how to manage API access permissions for users and services through Role-Based Access Control.
Jobs and CronJobs - Learn how to run and manage one-time batch tasks and schedule-based recurring tasks.
NetworkPolicy - Learn how to control Pod-to-Pod network traffic to strengthen cluster security.