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Running Kubernetes on Photon

(Note: Modified Getting started Kubernetes docs accordingly to run Kubernetes on Photon)

Table of Contents

Prerequisites

  1. You need 2 or more machines with Photon installed.

Instructions

This is a getting started guide for Photon. It is a manual configuration so you understand all the underlying packages / services / ports, etc...

This guide will only get ONE node (previously minion) working.

The Kubernetes package provides a few services: kube-apiserver, kube-scheduler, kube-controller-manager, kubelet, kube-proxy. These services are managed by systemd and the configuration resides in a central location: /etc/kubernetes. We will break the services up between the hosts. The first host, photon-master, will be the Kubernetes master. This host will run the kube-apiserver, kube-controller-manager, and kube-scheduler. In addition, the master will also run etcd (not needed if etcd runs on a different host but this guide assumes that etcd and Kubernetes master run on the same host). The remaining host, photon-node will be the node and run kubelet, proxy and docker.

System Information:

Hosts:

photon-master = 192.168.121.9
photon-node = 192.168.121.65

Prepare the hosts:

  • Install Kubernetes on all hosts - photon-{master,node}.
tdnf install kubernetes
  • Install etcd and iptables on photon-master
tdnf install etcd iptables
  • Install docker on photon-node
tdnf install docker
  • Add master and node to /etc/hosts on all machines (not needed if hostnames already in DNS). Make sure that communication works between photon-master and photon-node by using a utility such as ping.
echo "192.168.121.9	photon-master
192.168.121.65	photon-node" >> /etc/hosts
  • Edit /etc/kubernetes/config which will be the same on all hosts (master and node) to contain:
# Comma separated list of nodes in the etcd cluster
KUBE_MASTER="--master=http://photon-master:8080"

# logging to stderr means we get it in the systemd journal
KUBE_LOGTOSTDERR="--logtostderr=true"

# journal message level, 0 is debug
KUBE_LOG_LEVEL="--v=0"

# Should this cluster be allowed to run privileged docker containers
KUBE_ALLOW_PRIV="--allow_privileged=false"

Configure the Kubernetes services on the master.

  • Edit /etc/kubernetes/apiserver to appear as such. The service_cluster_ip_range IP addresses must be an unused block of addresses, not used anywhere else. They do not need to be routed or assigned to anything.
# The address on the local server to listen to.
KUBE_API_ADDRESS="--address=0.0.0.0"

# Comma separated list of nodes in the etcd cluster
KUBE_ETCD_SERVERS="--etcd_servers=http://127.0.0.1:4001"

# Address range to use for services
KUBE_SERVICE_ADDRESSES="--service-cluster-ip-range=10.254.0.0/16"

# Add your own!
KUBE_API_ARGS=""
  • Start the appropriate services on master:
for SERVICES in etcd kube-apiserver kube-controller-manager kube-scheduler; do
	systemctl restart $SERVICES
	systemctl enable $SERVICES
	systemctl status $SERVICES
done

  • Addition of nodes:

  • Create following node.json file on Kubernetes master node:

{
    "apiVersion": "v1",
    "kind": "Node",
    "metadata": {
        "name": "photon-node",
        "labels":{ "name": "photon-node-label"}
    },
    "spec": {
        "externalID": "photon-node"
    }
}

Now create a node object internally in your Kubernetes cluster by running:

$ kubectl create -f ./node.json

$ kubectl get nodes
NAME                LABELS              STATUS
photon-node         name=photon-node-label     Unknown

Please note that in the above, it only creates a representation for the node photon-node internally. It does not provision the actual photon-node. Also, it is assumed that photon-node (as specified in name) can be resolved and is reachable from Kubernetes master node. This guide will discuss how to provision a Kubernetes node (photon-node) below.

Configure the Kubernetes services on the node.

We need to configure the kubelet on the node.

  • Edit /etc/kubernetes/kubelet to appear as such:
###
# Kubernetes kubelet (node) config

# The address for the info server to serve on (set to 0.0.0.0 or "" for all interfaces)
KUBELET_ADDRESS="--address=0.0.0.0"

# You may leave this blank to use the actual hostname
KUBELET_HOSTNAME="--hostname_override=photon-node"

# location of the api-server
KUBELET_API_SERVER="--api_servers=http://photon-master:8080"

# Add your own!
#KUBELET_ARGS=""
  • Start the appropriate services on the node (photon-node).
for SERVICES in kube-proxy kubelet docker; do 
    systemctl restart $SERVICES
    systemctl enable $SERVICES
    systemctl status $SERVICES 
done
  • Check to make sure now the cluster can see the photon-node on photon-master, and its status changes to Ready.
kubectl get nodes
NAME                LABELS              STATUS
photon-node          name=photon-node-label     Ready
  • Deletion of nodes:

To delete photon-node from your Kubernetes cluster, one should run the following on photon-master (Please do not do it, it is just for information):

kubectl delete -f ./node.json

You should be finished!

The cluster should be running! Launch a test pod.

You should have a functional cluster, check out 101!