Add 'kubernetes-example/kubectl-intro.md'

kubernetes-example/kubectl-intro.md

@@ -0,0 +1,115 @@
+# Introduction to kubectl 
+
+## Deployment of the needed description in kubernetes
+
+These are two approaches to create the description in Kuberentes: 
+
+```bash
+# create a namespace 
+kubectl create namespace web-test
+
+# Then choose one of the following ways:
+# (1) Create the description
+kubectl create -f nginx.yml -f service.yml
+
+# (2) Create or update descriptions if existing
+kubectl apply -f nginx.yml -f service.yml
+```
+
+## To show it is working
+
+Here are some useful commands:
+
+```bash
+# show nodes
+kubectl get nodes
+
+# show pods for our namespace
+kubectl get -n web-test pods 
+
+# show deployments for our namespace
+kubectl get -n web-test deployment
+
+# show services for our namespace
+kubectl get -n web-test service
+
+# show logs of deployed nginx instances
+kubectl logs -n web-test deployment/nginx-deployment
+```
+
+## Scaling up and down
+
+```bash
+# scale up instances to 5
+kubectl scale deployment/nginx-deployment --replicas=5
+
+# scale down instances again to 3
+kubectl scale deployment/nginx-deployment --replicas=3
+
+```
+
+
+## To see it is working in the browser ;)
+
+The nginx instances are reachable at the floating ips of the **node**-instances at port **30007** in our case.
+
+
+## Many other things can be done ;)
+
+- Autoscaling 
+- Detailled Service functions (LoadBalancer, ...)
+- Dashboard
+- FaaS Setup ;) 
+- ...
+
+
+## Appendix
+
+### Nginx description
+
+*nginx.yml:*
+```yml
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx-deployment
+  namespace: web-test
+spec:
+  selector:
+    matchLabels:
+      app: nginx-deployment
+  replicas: 3 # tells deployment to run 3 pods matching the template
+  template:
+    metadata:
+      labels:
+        app: nginx-deployment
+    spec:
+      containers:
+      - name: nginx
+        image: nginx:latest
+        ports:
+        - containerPort: 80
+
+```
+
+### Nginx service description
+
+*service.yml:*
+```yml
+apiVersion: v1
+kind: Service
+metadata:
+  name: nginx-service
+  namespace: web-test
+spec:
+  type: NodePort
+  selector:
+    app: nginx-deployment
+  ports:
+      # By default and for convenience, the `targetPort` is set to the same value as the `port` field.
+    - port: 80
+      targetPort: 80
+      # Optional field
+      # By default and for convenience, the Kubernetes control plane will allocate a port from a range (default: 30000-32767)
+      nodePort: 30007
+```