Kubernetes object

 Kubernetes is a powerful container orchestration platform that uses various objects to manage the deployment, scaling, and operation of application containers. Here’s a step-by-step guide to some of the key Kubernetes objects with examples:

1. Pod

A Pod is the smallest and simplest Kubernetes object. It represents a single instance of a running process in your cluster.

Example:

Create a file named pod-example.yaml:

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
  - name: my-container
    image: nginx:latest
    ports:
    - containerPort: 80

Commands:

kubectl apply -f pod-example.yaml
kubectl get pods
kubectl describe pod my-pod

2. Service

A Service is an abstraction that defines a logical set of Pods and a policy by which to access them. This can be used to expose your application.

Example:

Create a file named service-example.yaml:

apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  selector:
    app: my-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: ClusterIP

Commands:

kubectl apply -f service-example.yaml
kubectl get services
kubectl describe service my-service

3. Deployment

A Deployment provides declarative updates to Pods and ReplicaSets. It manages the deployment of Pods and ensures the desired state is maintained.

Example:

Create a file named deployment-example.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-container
        image: nginx:latest
        ports:
        - containerPort: 80

Commands:

kubectl apply -f deployment-example.yaml
kubectl get deployments
kubectl describe deployment my-deployment

4. ReplicaSet

A ReplicaSet ensures that a specified number of pod replicas are running at any given time. Deployments manage ReplicaSets and Pods.

Example:

Create a file named replicaset-example.yaml:

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: my-replicaset
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-container
        image: nginx:latest
        ports:
        - containerPort: 80

Commands:

kubectl apply -f replicaset-example.yaml
kubectl get replicasets
kubectl describe replicaset my-replicaset

5. StatefulSet

A StatefulSet is used for managing stateful applications. It provides guarantees about the ordering and uniqueness of Pods.

Example:

Create a file named statefulset-example.yaml:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: my-statefulset
spec:
  serviceName: "my-service"
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-container
        image: nginx:latest
        ports:
        - containerPort: 80

Commands:

kubectl apply -f statefulset-example.yaml
kubectl get statefulsets
kubectl describe statefulset my-statefulset

6. ConfigMap

A ConfigMap allows you to separate configuration artifacts from image content to keep containerized applications portable.

Example:

Create a file named configmap-example.yaml:

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-configmap
data:
  my-key: my-value

Commands:

kubectl apply -f configmap-example.yaml
kubectl get configmaps
kubectl describe configmap my-configmap

7. Secret

A Secret is used to store and manage sensitive information, such as passwords, OAuth tokens, and ssh keys.

Example:

Create a file named secret-example.yaml:

apiVersion: v1
kind: Secret
metadata:
  name: my-secret
type: Opaque
data:
  my-key: bXktdmFsdWU= # base64 encoded value of "my-value"

Commands:

kubectl apply -f secret-example.yaml
kubectl get secrets
kubectl describe secret my-secret

8. Namespace

A Namespace provides a mechanism for isolating groups of resources within a single cluster.

Example:

Create a file named namespace-example.yaml:

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

Commands:

kubectl apply -f namespace-example.yaml
kubectl get namespaces
kubectl describe namespace my-namespace

9. Ingress

An Ingress manages external access to services, typically HTTP. It provides load balancing, SSL termination, and name-based virtual hosting.

Example:

Create a file named ingress-example.yaml:

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

Commands:

kubectl apply -f ingress-example.yaml
kubectl get ingress
kubectl describe ingress my-ingress

10. Job

A Job creates one or more Pods and ensures that a specified number of them successfully terminate.

Example:

Create a file named job-example.yaml:

apiVersion: batch/v1
kind: Job
metadata:
  name: my-job
spec:
  template:
    spec:
      containers:
      - name: my-container
        image: busybox
        command: ["sh", "-c", "echo Hello Kubernetes! && sleep 30"]
      restartPolicy: OnFailure

Commands:

kubectl apply -f job-example.yaml
kubectl get jobs
kubectl describe job my-job

11. CronJob

A CronJob creates Jobs on a scheduled time, similar to cron in Linux.

Example:

Create a file named cronjob-example.yaml:

apiVersion: batch/v1
kind: CronJob
metadata:
  name: my-cronjob
spec:
  schedule: "*/5 * * * *" # every 5 minutes
  jobTemplate:
    spec:
      template:
        spec:
          containers:
          - name: my-container
            image: busybox
            command: ["sh", "-c", "echo Hello Kubernetes! && sleep 30"]
          restartPolicy: OnFailure

Commands:

kubectl apply -f cronjob-example.yaml
kubectl get cronjobs
kubectl describe cronjob my-cronjob