kubernates(K8s) resources Overview with examples with explanation

Category : Kubernetes | Sub Category : Kubernetes With Java | By Prasad Bonam Last updated: 2023-11-17 08:23:58 Viewed : 524

1. Pod:

A Pod is the smallest deployable unit in Kubernetes, representing a single instance of a running process. It can contain one or more containers.

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apiVersion: v1
kind: Pod
metadata:
  name: example-pod
spec:
  containers:
    - name: nginx-container
      image: nginx

Explanation:

• This YAML file defines a basic Pod named "example-pod."
• It contains a single container named "nginx-container," which runs the Nginx image.

2. Service:

A Service exposes a set of Pods as a network service. It allows other applications to discover and communicate with the Pods.

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

Explanation:

• This YAML file creates a Service named "example-service."
• It selects Pods with the label "app: example-app" and exposes them on port 80, forwarding traffic to port 8080 in the selected Pods.

3. Namespace:

A Namespace provides a way to divide cluster resources between multiple users or teams.

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apiVersion: v1
kind: Namespace
metadata:
  name: example-namespace

Explanation:

• This YAML file creates a Namespace named "example-namespace."

4. Deployment:

A Deployment manages the deployment and scaling of Pods, allowing declarative updates to applications.

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apiVersion: apps/v1
kind: Deployment
metadata:
  name: example-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: example-app
  template:
    metadata:
      labels:
        app: example-app
    spec:
      containers:
        - name: nginx-container
          image: nginx

Explanation:

• This YAML file creates a Deployment named "example-deployment."
• It ensures there are three replicas of Pods with the label "app: example-app," each running the Nginx container.

5. ReplicaSet:

A ReplicaSet ensures a specified number of replicas of a Pod are running.

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apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: example-replicaset
spec:
  replicas: 2
  selector:
    matchLabels:
      app: example-app
  template:
    metadata:
      labels:
        app: example-app
    spec:
      containers:
        - name: nginx-container
          image: nginx

Explanation:

• This YAML file creates a ReplicaSet named "example-replicaset."
• It ensures there are two replicas of Pods with the label "app: example-app," each running the Nginx container.

6. ConfigMap:

A ConfigMap allows you to decouple configuration artifacts from the container image.

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apiVersion: v1
kind: ConfigMap
metadata:
  name: example-configmap
data:
  key1: value1
  key2: value2

Explanation:

• This YAML file creates a ConfigMap named "example-configmap."
• It defines key-value pairs (key1: value1, key2: value2) that can be used as configuration data in Pods.

7. Secret:

A Secret stores sensitive information, such as passwords or API keys, in a Base64-encoded format.

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apiVersion: v1
kind: Secret
metadata:
  name: example-secret
type: Opaque
data:
  username: <base64-encoded-username>
  password: <base64-encoded-password>

Explanation:

• This YAML file creates a Secret named "example-secret" with a username and password encoded in Base64 format.

8. Volume:

A Volume is a directory that is accessible to containers in a Pod, providing a way to persist data.

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apiVersion: v1
kind: Pod
metadata:
  name: example-pod
spec:
  containers:
    - name: nginx-container
      image: nginx
      volumeMounts:
        - name: example-volume
          mountPath: /usr/share/nginx/html
  volumes:
    - name: example-volume
      emptyDir: {}

Explanation:

• This YAML file defines a Pod with an Nginx container and an emptyDir Volume mounted at "/usr/share/nginx/html."

9. Ingress:

An Ingress provides HTTP and HTTPS routing to services based on rules, enabling external access to services in a cluster.

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apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
    - host: example.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: example-service
                port:
                  number: 80

Explanation:

• This YAML file creates an Ingress named "example-ingress."
• It defines a rule for routing HTTP traffic from "example.com" to the Service named "example-service" on port 80.

These examples cover some of the fundamental Kubernetes resources and how they are configured. You can customize these examples based on your specific application requirements.