Added configs

services-in-kubernetes/01/demos.md

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+# 1. Create a Deployment of nginx
+kubectl create deployment my-nginx --image=nginx:latest --port=80
+
+# 2. Expose the Deployment as a NodePort service
+kubectl expose deployment my-nginx \
+  --type=NodePort \
+  --port=80 \
+  --target-port=80 \
+  --name=my-nginx-service
+
+===============
+# backend-deployment.yaml
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: backend
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: backend
+  template:
+    metadata:
+      labels:
+        app: backend
+    spec:
+      containers:
+      - name: http-echo
+        image: hashicorp/http-echo:0.2.3
+        args:
+          - "-listen=:8080"
+          - "-text=Hello from the Backend!"
+        ports:
+        - containerPort: 8080
+-------------
+
+# backend-service.yaml
+apiVersion: v1
+kind: Service
+metadata:
+  name: backend-service
+spec:
+  type: ClusterIP  # Default
+  selector:
+    app: backend
+  ports:
+    - port: 80         # Service port (used by internal clients)
+      targetPort: 8080 # Container port in the backend Pod
+------------
+# frontend-deployment.yaml
+-------
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: frontend
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: frontend
+  template:
+    metadata:
+      labels:
+        app: frontend
+    spec:
+      containers:
+      - name: curl-loop
+        image: curlimages/curl:7.86.0
+        command: ["/bin/sh"]
+        args:
+          - "-c"
+          - |
+            while true; do
+              echo "=== Calling backend-service:80 ==="
+              curl -s backend-service:80
+              echo
+              sleep 5
+            done
+-----------
+