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Containerization-Orchestration/Kubernetes/workloads/09-Services.md

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+# 🔗 **Kubernetes Services (SVC)**
+
+A **Service** in Kubernetes provides a stable network endpoint to access a set of Pods. It abstracts access through selectors and DNS names, enabling loose coupling between client applications and Pods.
+
+---
+
+## 🌐 **Service Basics**
+
+### 📌 **Service Flow**
+
+```
+Service ➡️ Endpoint ➡️ Pods
+```
+
+* Services **group Pods** behind a single access point.
+* They get a **cluster-wide DNS name** automatically.
+* Use **label selectors** to forward traffic to matching Pods.
+
+---
+
+## 🧭 **Types of Services**
+
+1. **ClusterIP** (default)
+
+   * Only reachable within the cluster.
+
+2. **NodePort**
+
+   * Exposes the service via a static port on each node.
+
+3. **LoadBalancer**
+
+   * Creates an external IP address using a cloud provider.
+
+---
+
+## 🧪 **Useful Commands**
+
+### 🔍 Get Endpoints
+
+```bash
+kubectl get ep -n <namespace>
+```
+
+### 📄 Get Services
+
+```bash
+kubectl get svc -n <namespace>
+```
+
+
+```bash
+kubectl expose deployment web-server-dep -n dev --port 80 
+```
+
+
+
+---
+
+## 🔁 **Port Forwarding**
+
+To access a service from your local machine, forward a local port to the service port:
+
+```bash
+kubectl port-forward -n <namespace> svc/<service-name> <local-port>:<target-port>
+```
+
+> **Example:**
+> Forward local port `8080` to port `80` of `my-service` in the `mynamespace` namespace:
+>
+> ```bash
+> kubectl port-forward -n mynamespace svc/my-service 8080:80
+> ```
+
+You can also bind to all network interfaces:
+
+```bash
+kubectl port-forward -n <namespace> svc/nginx 80:80 --address 0.0.0.0
+```
+
+> 🌐 **DNS format:**
+> `<service-name>.<namespace>.svc.cluster.local`
+
+---
+
+## 🧾 **Example Service Manifest**
+
+```yaml
+apiVersion: v1
+kind: Service
+metadata:
+  name: nginx
+  namespace: ns
+  labels:
+    app: web-server
+spec:
+  type: ClusterIP  # Options: ClusterIP, NodePort, LoadBalancer
+  selector:
+    app: nginx
+  ports:
+    - name: http
+      port: 80
+      targetPort: 8080
+```
+
+> 🔍 **Note:** The `selector` must match the labels of the target Pods.
+> 🧠 **Tip:** Use `kubectl describe svc <service-name>` to inspect the service and verify connectivity.
+
+
+
+```yaml
+apiVersion: v1
+kind: Service
+metadata:
+  name: nginx
+  namespace: ns
+  labels:
+    app: web-server
+spec:
+  type: LoadBalancer
+  selector:
+    app: nginx
+  ports:
+    - name: http
+      port: 80
+      targetPort: 8080
+```
+
+```yaml
+apiVersion: v1
+kind: Service
+metadata:
+  name: db-svc
+  namespace: db
+spec:
+  type: NodePort
+  ports:
+    - name: sql
+      port: 3306
+      targetPort: 3306
+      nodePort: 30000
+  selector:
+    app: db
+```