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Configuring Kubernetes on Fedora via Ansible

Configuring Kubernetes on Fedora via Ansible offers a simple way to quickly create a clustered environment with little effort.

Table of Contents

Prerequisites

  1. Host able to run ansible and able to clone the following repo: kubernetes
  2. A Fedora 21+ host to act as cluster master
  3. As many Fedora 21+ hosts as you would like, that act as cluster nodes

The hosts can be virtual or bare metal. Ansible will take care of the rest of the configuration for you - configuring networking, installing packages, handling the firewall, etc. This example will use one master and two nodes.

Architecture of the cluster

A Kubernetes cluster requires etcd, a master, and n nodes, so we will create a cluster with three hosts, for example:

master,etcd = kube-master.example.com
    node1 = kube-node-01.example.com
    node2 = kube-node-02.example.com

Make sure your local machine has

  • ansible (must be 1.9.0+)
  • git
  • python-netaddr

If not

yum install -y ansible git python-netaddr

Now clone down the Kubernetes repository

git clone https://github.com/kubernetes/contrib.git
cd contrib/ansible

Tell ansible about each machine and its role in your cluster

Get the IP addresses from the master and nodes. Add those to the ~/contrib/ansible/inventory file on the host running Ansible.

[masters]
kube-master.example.com

[etcd]
kube-master.example.com

[nodes]
kube-node-01.example.com
kube-node-02.example.com

Setting up ansible access to your nodes

If you already are running on a machine which has passwordless ssh access to the kube-master and kube-node-{01,02} nodes, and 'sudo' privileges, simply set the value of ansible_ssh_user in ~/contrib/ansible/group_vars/all.yaml to the username which you use to ssh to the nodes (i.e. fedora), and proceed to the next step...

Otherwise setup ssh on the machines like so (you will need to know the root password to all machines in the cluster).

edit: ~/contrib/ansible/group_vars/all.yml

ansible_ssh_user: root

Configuring ssh access to the cluster

If you already have ssh access to every machine using ssh public keys you may skip to setting up the cluster

Make sure your local machine (root) has an ssh key pair if not

ssh-keygen

Copy the ssh public key to all nodes in the cluster

for node in kube-master.example.com kube-node-01.example.com kube-node-02.example.com; do
  ssh-copy-id ${node}
done

Setting up the cluster

Although the default value of variables in ~/contrib/ansible/group_vars/all.yml should be good enough, if not, change them as needed.

edit: ~/contrib/ansible/group_vars/all.yml

Configure access to kubernetes packages

Modify source_type as below to access kubernetes packages through the package manager.

source_type: packageManager

Configure the IP addresses used for services

Each Kubernetes service gets its own IP address. These are not real IPs. You need only select a range of IPs which are not in use elsewhere in your environment.

kube_service_addresses: 10.254.0.0/16

Managing flannel

Modify flannel_subnet, flannel_prefix and flannel_host_prefix only if defaults are not appropriate for your cluster.

Managing add on services in your cluster

Set cluster_logging to false or true (default) to disable or enable logging with elasticsearch.

cluster_logging: true

Turn cluster_monitoring to true (default) or false to enable or disable cluster monitoring with heapster and influxdb.

cluster_monitoring: true

Turn dns_setup to true (recommended) or false to enable or disable whole DNS configuration.

dns_setup: true

Tell ansible to get to work!

This will finally setup your whole Kubernetes cluster for you.

cd ~/contrib/ansible/

./setup.sh

Testing and using your new cluster

That's all there is to it. It's really that easy. At this point you should have a functioning Kubernetes cluster.

Show kubernetes nodes

Run the following on the kube-master:

kubectl get nodes

Show services running on masters and nodes

systemctl | grep -i kube

Show firewall rules on the masters and nodes

iptables -nvL

Create /tmp/apache.json on the master with the following contents and deploy pod

{
  "kind": "Pod",
  "apiVersion": "v1",
  "metadata": {
    "name": "fedoraapache",
    "labels": {
      "name": "fedoraapache"
    }
  },
  "spec": {
    "containers": [
      {
        "name": "fedoraapache",
        "image": "fedora/apache",
        "ports": [
          {
            "hostPort": 80,
            "containerPort": 80
          }
        ]
      }
    ]
  }
}
kubectl create -f /tmp/apache.json

Check where the pod was created

kubectl get pods

Check Docker status on nodes

docker ps
docker images

After the pod is 'Running' Check web server access on the node

curl http://localhost

That's it !

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