Guide to creating a Kubernetes cluster on a coreos instance on Digital Ocean with three nodes.

Creating coreos cluster on Digital Ocean

1. Create a node with the following configuration

• 1GB/1CPU 30GB 2TB nodehttps://discovery.etcd.io/new?size=3
• Select an appropriate region
• CoreOS 76.4.0(Stable release)
• Turn on private networking
• Select User Data option
• In the textbox for user data provide information as specidied in this file
  • Use this URL https://discovery.etcd.io/new?size=3 to generate a discovery token. The 3 at the end of the token specifies the number of nodes that are to be present while initiating the cluster. A minimum of these many number of nodes should be present in the cluster for it to be connected through fleet.
  • Replace the token generated above in line 7 of the cloud-config file.
• CoreOS instances can only be connected to via ssh and hence a public-key needs to be set up in the digital ocean dashboard. Use this link to learn how to setup ssh keys with digital ocean.
• In a similar manner create 2 more nodes.

2. Once the nodes are created you can securely connect to them using ssh. ssh -A core@public-ip-address
3. Once you are connected to the device you can clone this repository
   git clone https://github.com/jiteshmohan/kubernetes-do.git
4. Create a new directory /opt/bin/
sudo mkdir -p /opt/bin/
5. cd kubernetes-do
6. Copy all files from the folder executables into the /opt/bin/ directory.
   sudo cp executables/* /opt/bin/
7. Next you need to copy the service files to /etc/systemd/system/. However the files are separate for master and minion.

• On the master: sudo cp service-files/master/*.service /etc/systemd/system/
• On minion: sudo cp service-files/minion/*.service /etc/systemd/system/

8. Digital ocean creates a file /etc/environment when spawning the instance. The contents of this file are as follows:

   $ cat /etc/environment
   COREOS_PRIVATE_IPV4=<ip_addr>
   COREOS_PUBLIC_IPV4=<ip_addr>
   

   To this file add additional two lines in the case of the minion. The lines that need to be added are

   MASTER_PUBLIC_IPV4=<ip_addr>
   MASTER_PRIVATE_IPV4=<ip_addr>
   

9. Ensure that all the executable copied into /opt/bin have execute permissions.
10. Enable the services that we created.

    cd /etc/systemd/system
    sudo systemctl enable *
    

11. On master start the following services

    sudo systemctl restart flanneld
    sudo systemctl restart docker
    sudo systemctl restart kube-apiserver
    sudo systemctl restart kube-controller-manager
    sudo systemctl restart kube-scheduler
    sudo systemctl restart kube-proxy
    sudo systemctl restart kubelet

12. On the minions start the following services

    sudo systemctl restart flanneld
    sudo systemctl restart docker
    sudo systemctl restart kube-scheduler
    sudo systemctl restart kube-proxy
    sudo systemctl restart kubelet

13. After starting all the above services use

    systemctl status <service-name>

    to check the status of each service.
14. On the master run the following command to get the list of machines in the kubernetes cluster.

    kubectl get nodes

15. To access the Kubernetes dashboard perform the following steps

    cd
    git clone https://github.com/kubernetes/kubernetes.git
    cd kubernetes
    kubectl create -f cluster/addons/kube-ui/kube-ui-rc.yaml --namespace=kube-system
    kubectl create -f cluster/addons/kube-ui/kube-ui-svc.yaml --namespace=kube-system

16. To access the UI use the link https://<master-public-ip>:6443/ui/

Screencast

References

• https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-kubernetes-on-top-of-a-coreos-cluster
• https://www.digitalocean.com/community/tutorials/how-to-set-up-a-coreos-cluster-on-digitalocean
• http://kubernetes.io/v1.0/docs/user-guide/ui.html