Kubernetes Overview

A Kubernetes setup is made up of multiple layers, from the overall cluster down to the containers actually running your application. This diagram shows the relationships between clusters, namespaces, deployments, services, pods, and containers, and explains how manifest files (deployment.yaml and service.yaml) control what’s deployed.

+===============================================================+
|                           CLUSTER                             |
+===============================================================+
| A complete Kubernetes environment, containing:               |
| - Control Plane (API Server, Scheduler, Controller Manager)   |
| - Worker Nodes (run workloads in Pods)                        |
| Manages the state of workloads and networking across all nodes |
+===============================================================+
                               |
                               v
                  (Many logical partitions per cluster)
        +-------------------+           +-------------------+
        |   NAMESPACE: A    |           |   NAMESPACE: B    |   ...
        +-------------------+           +-------------------+
| Logical partition inside a cluster to organize & isolate      |
| resources. Useful for separating apps, teams, or environments |
+----------------------------------------------------------------+
                 |
                 |  Deploy resources into a namespace:
                 |    kubectl apply -f deployment.yaml  [-n A]
                 |    kubectl apply -f service.yaml     [-n A]
                 v
     +----------------------+        +----------------------+
     |   deployment.yaml    |        |     service.yaml     |
     |  Kind: Deployment    |        |  Kind: Service       |
     |  apiVersion: apps/v1 |        |  apiVersion: v1      |
     |  Defines desired     |        |  Exposes Pods to     |
     |  Pods & replicas     |        |  internal/external   |
     +----------+-----------+        +----------+-----------+
                | creates                         | selects Pods by label
                v                                  (e.g., app=web)
        +--------------------+                    |
        |     Deployment     |--------------------+
        +--------------------+                    |
| Ensures desired number of Pod replicas run      |
| Updates Pods in a controlled, rolling manner    |
+-------------------------------------------------+
                | creates
                v
        +--------------------+
        |     ReplicaSet     |
        +--------------------+
| Tracks a set of Pods created from the same spec |
| Created/managed automatically by a Deployment  |
+-------------------------------------------------+
                | spawns N replicas
                v
        +--------------------+
        |        Pod         |
        |  +--------------+  |
        |  |  Container   |  |
        |  +--------------+  |
        |  |  Container   |  |
        |  +--------------+  |
        +--------------------+
| Smallest deployable unit in Kubernetes.          |
| Holds one or more containers that share storage, |
| network, and specs.                              |
+--------------------------------------------------+
                      ^
                      | labels (e.g., app=web, tier=fe)
                      +----------------------------------+
                                   |
                             +-------------+
                             |   Service   |
                             +-------------+
| Stable networking endpoint that routes to Pods via label selector |
| Types: ClusterIP, NodePort, LoadBalancer, etc.                    |
+-------------------------------------------------------------------+

Key Concepts

  • Cluster
    The top-level Kubernetes environment containing all nodes and system components. Responsible for orchestrating workloads and networking.
  • Namespace
    A logical boundary within a cluster for isolating resources. Lets multiple teams or projects share a cluster without interfering with each other.
  • Deployment (deployment.yaml)
    A higher-level controller that defines how many Pod replicas should be running and handles updates. The YAML specifies things like:
    • apiVersion: apps/v1
    • kind: Deployment
    • Pod template (containers, images, labels)
  • ReplicaSet
    Maintains a stable set of replica Pods. Created and managed automatically by Deployments.
  • Pod
    The smallest deployable unit. A Pod wraps one or more containers, along with shared storage and network.
  • Container
    A lightweight, isolated runtime environment for your application. Usually runs a single process (like your web server).
  • Service (service.yaml)
    A stable networking abstraction. Matches Pods using labels and exposes them internally or externally.
How’re service.yaml and deployment.yaml related ?

They’re Linked via Labels/Selectors

  • In deployment.yaml → Pod template metadata has labels (e.g., app: web).
  • In service.yaml → spec.selector must match those labels (e.g., app: web).
  • This relationship is the only way a Service knows which Pods belong to it.

Useful commands to remember

  • View Kubernetes deployments - kubectl get deployments
  • View pods - kubectl get pods
  • View cluster events - kubectl get events
  • View kubectl configuration - kubectl config view
  • View application logs for a container in a pod - kubectl logs <pod name>
  • To expose the pod to internet/local network - kubectl expose deployment <deployment name> --type=LoadBalancer --port=<port number>
  • View services in the cluster - kubectl get services
  • To list available add-ons - minikube addons list
  • To enable an add-on - minikube addons enable <add-on name>
  • To remove the deployment and service created - 
    kubectl delete service <service name>
kubectl delete deployment <deployment name>
  • To scale a deployment in kubernetes - kubectl scale -n <namespace> deployment <deployment name> --replicas=<no.of replicas (i.e., 10,20.....)>
  • To launch dashboard - minikube dashboard