Core Kubernetes Objects

1. Pod:

   • A Pod is the smallest deployable unit in Kubernetes and represents one or more containers running together.

   • Shared resources in a Pod:

     • Storage: Volumes shared among containers.

     • Network: Containers share the same IP and port space.

   Example Pod YAML manifest:

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

2. Service:

   • Abstracts access to a set of Pods as a single network service.

   • Types of Services:

     • ClusterIP: Internal access within the cluster.

     • NodePort: Exposes the Service on each Node’s IP at a static port.

     • LoadBalancer: Provisions an external load balancer (cloud-specific).

   Example Service YAML manifest:

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

3. Deployment:

   • Manages the deployment and scaling of Pods.

   • Allows rolling updates and rollbacks.

   Example Deployment YAML manifest:

   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

4. StatefulSet:

   • Manages stateful applications, ensuring Pods are deployed in a specific order and maintain unique identities.

5. ConfigMap and Secret:

   • ConfigMap: Stores configuration data as key-value pairs.

   • Secret: Stores sensitive data such as passwords and API keys.

Activity:

Create a Deployment YAML file to deploy three replicas of an Nginx container. Apply it using kubectl apply -f and verify the Pods are running.