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Running Kubernetes on Photon OS

The procedure describes how to break the services up between the hosts.

The first host, photon-master, is the Kubernetes master. This host runs the kube-apiserver, kube-controller-manager, and kube-scheduler. In addition, the master also runs etcd. Although etcd is not needed on the master if etcd runs on a different host, this guide assumes that etcd and the Kubernetes master run on the same host. The remaining host, photon-node, is the node and runs kubelet, proxy, and docker.

1 - System Information

Hosts:

photon-master = 192.168.121.9
photon-node = 192.168.121.65

2 - Prepare the Hosts

The following packages have to be installed. If the tdnf command returns “Nothing to do,” the package is already installed.

  • Install Kubernetes on all hosts (both photon-master and photon-node).

    tdnf install kubernetes
    
  • Install iptables on photon-master and photon-node:

    tdnf install iptables
    
  • Open the tcp port 8080 (api service) on the photon-master in the firewall

    iptables -A INPUT -p tcp --dport 8080 -j ACCEPT
    
  • Open the tcp port 10250 (api service) on the photon-node in the firewall

    iptables -A INPUT -p tcp --dport 10250 -j ACCEPT
    
  • Install Docker on photon-node:

    tdnf install docker
    
  • Add master and node to /etc/hosts on all machines (not needed if the hostnames are 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 the hosts (master and node), so that it contains the following lines:

    # Comma separated list of nodes in the etcd cluster
    KUBE_MASTER="--master=http://photon-master:8080"
    
    # logging to stderr routes it to 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"
    

3 - Configure Kubernetes Services on the Master

Perform the following steps to configure Kubernetes services on the master:

  1. 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=""
    
  2. Start the appropriate services on master:

    for SERVICES in etcd kube-apiserver kube-controller-manager kube-scheduler; do
        emctl restart $SERVICES
        emctl enable $SERVICES
        emctl status $SERVICES
    done
    
  3. To add the other node, create the following node.json file on the Kubernetes master node:

    {
        "apiVersion": "v1",
        "kind": "Node",
        "metadata": {
            "name": "photon-node",
            "labels":{ "name": "photon-node-label"}
        },
        "spec": {
            "externalID": "photon-node"
        }
    }
    
  4. Create a node object internally in your Kubernetes cluster by running the following command:

    $ kubectl create -f ./node.json
    
    $ kubectl get nodes
    NAME                LABELS              STATUS
    photon-node         name=photon-node-label     Unknown
    

Note: The above example 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 the Kubernetes master node.

4 - Configure the Kubernetes services on Node

Perform the following steps to configure the kubelet on the node:

  1. Edit /etc/kubernetes/kubelet to appear like this:

    ###
    # 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="--kubeconfig=/etc/kubernetes/kubeconfig"
    
    # Add your own
    #KUBELET_ARGS=""
    
  2. Make sure that the api-server end-point located in /etc/kubernetes/kubeconfig, targets the api-server in the master node and does not fall into the loopback interface:

    apiVersion: v1
    clusters:
    - cluster:
        server: <ip_master_node>:8080
    
  3. 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
    
  4. Check to make sure that the cluster can now see the photon-node on photon-master and that its status changes to Ready.

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

    If the node status is NotReady, verify that the firewall rules are permissive for Kubernetes.

    • 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
    

Result

You should have a functional cluster. You can now launch a test pod. For an introduction to working with Kubernetes, see Kubernetes documentation.