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# 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 way:
# (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 show -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
```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
```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: 3000 ```
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