Exposing the Pod, Installing Worker Nodes and Scaling the Cluster

NAME LABELS STATUS AGE 127.0.0.1 kubernetes.io/hostname=127.0.0.1 Ready 1h An easy way to test the cluster is by running a busybox docker image for ARM. kubectl run can be used to run the image as a container in a pod. kubectl get pods shows the pods that are registered with its status. $ kubectl run busybox --image=hypriot/rpi-busybox-httpd $ kubectl get pods -o wide NAME READY STATUS RESTARTS AGE NODE busybox-fry54 1/1 Running 1 1h 127.0.0.1 k8s-master-127.0.0.1 3/3 Running 6 1h 127.0.0.1 ``` Now the pod is running but the application is not generally accessible. That can be achieved by creating a service. The cluster IP-address is the IP-address the service is avalailable within the cluster. Use the IP-address of your master node as external IP and the service becomes available outside of the cluster (e.g. at http://192.168.192.161 in my case). ``` $ kubectl expose rc busybox --port=90 --target-port=80 --external-ip=\<ip-address-master-node\> $ kubectl get svc NAME CLUSTER\_IP EXTERNAL\_IP PORT(S) SELECTOR AGE busybox 10.0.0.87 192.168.192.161 90/TCP run=busybox 1h kubernetes 10.0.0.1 \<none\> 443/TCP \<none\> 2h $ curl http://10.0.0.87:90/ ``` ``` \<html\> \<head\>\<title\>Pi armed with Docker by Hypriot\</title\> \<body style="width: 100%; background-color: black;"\> \<div id="main" style="margin: 100px auto 0 auto; width: 800px;"\> \<img src="pi\_armed\_with\_docker.jpg" alt="pi armed with docker" style="width: 800px"\> \</div\> \</body\> \</html\> ``` ### Installing the Kubernetes worker nodes The next step is installing Kubernetes on each worker node and add it to the cluster. This also comes basically down to getting the git repository content and executing the installation script. Though in this installation the k8s.conf file needs to be copied on forehand and edited to contain the IP-address of the master node. ``` $ curl -L -o k8s-on-rpi.zip https://github.com/awassink/k8s-on-rpi/archive/master.zip $ apt-get update $ apt-get install unzip $ unzip k8s-on-rpi.zip $ mkdir /etc/kubernetes $ cp k8s-on-rpi-master/rootfs/etc/kubernetes/k8s.conf /etc/kubernetes/k8s.conf ``` ### Change the ip-address in /etc/kubernetes/k8s.conf to match the master node ### ``` $ k8s-on-rpi-master/install-k8s-worker.sh ``` The install script will install four services. These are the quite similar to ones on the master node, but with the difference that no etcd service is running and the kubelet service is configured as worker node. Once all the services on the worker node are up and running we can check that the node is added to the cluster on the master node. ``` $ kubectl get nodes NAME LABELS STATUS AGE 127.0.0.1 kubernetes.io/hostname=127.0.0.1 Ready 2h 192.168.192.160 kubernetes.io/hostname=192.168.192.160 Ready 1h $ kubectl scale --replicas=2 rc/busybox $ kubectl get pods -o wide NAME READY STATUS RESTARTS AGE NODE busybox-fry54 1/1 Running 1 1h 127.0.0.1 busybox-j2slu 1/1 Running 0 1h 192.168.192.160 k8s-master-127.0.0.1 3/3 Running 6 2h 127.0.0.1 ``` ### Enjoy your Kubernetes cluster! Congratulations! You now have your Kubernetes Raspberry Pi cluster running and can start playing with Kubernetes and start learning. Checkout the [Kubernetes User Guide](https://github.com/kubernetes/kubernetes/blob/master/docs/user-guide/README.md) to find out what you all can do. And don’t forget to pull some plugs occasionally like Ray and I do :-)

This section covers exposing the running pod as a service using kubectl, allowing external access to the application. It also explains how to install Kubernetes on worker nodes, configure them to connect to the master node, and verify their addition to the cluster. Finally, it demonstrates scaling the application by increasing the number of replicas and showcases how pods are distributed across the master and worker nodes.