How to install Kubernetes using Let’s Kube script

Published in

Containerum

4 min readJul 5, 2018

by Dmitry Timofeiev

Let’s Kube is a set of Ansible playbooks that bootstrap a Kubernetes cluster in a matter of minutes. Let’s Kube installs docker, etcd store, the core Kubernetes components (kubelet, kubectl, kubeadm, etcd), and calico — a network plug-in for network security.

In this guide we will install Ansible and then proceed to bootstrapping K8s with Let’s Kube.

Prerequisites

To run Let’s Kube you need to have 3 virtual machines with CentOS 7 and a machine with Git installed.

Install Ansible

If your machine runs on CentOS, then install Ansible from epel-release repo:

yum install epel-release

and then run:

yum install ansible

You can also build your own rpm package from source code:

$ git clone git://github.com/ansible/ansible.git — recursive
$ cd ./ansible
$ make rpm
$ sudo rpm -Uvh ./rpm-build/ansible-*.noarch.rpm

To install Ansible on Ubuntu run:

$ sudo apt-get install software-properties-common
$ sudo apt-add-repository ppa:ansible/ansible
$ sudo apt-get update
$ sudo apt-get install ansible

If you use Debian, first add the repo to edit /etc/apt/sources.list:

deb http://ppa.launchpad.net/ansible/ansible/ubuntu trusty main

Then run:

$ sudo apt-key adv — keyserver keyserver.ubuntu.com — recv-keys 93C4A3FD7BB9C367
$ sudo apt-get update
$ sudo apt-get install ansible

To install Ansible on other OS, refer to the official docs.

Let’s Kube

Preparation

First, clone the project repo from GitHub:

git clone https://github.com/containerum/letskube.git

Cd to the letskube directory and edit the inventory file:

[all]
m1 ansible_user=centos ansible_host=172.16.0.1 ansible_port=22 ip_internal=10.0.0.1
s1 ansible_user=centos ansible_host=172.16.0.2 ansible_port=22 ip_internal=10.0.0.2[masters]
m1[slaves]
s1[kubectl]
m1

In [all] set the hostname and credentials for accessing the remote machine:

ansible_user — user for authorization with ansible.
ansible_host — external IP address of the remote machine.
ansible_port — SSH port to establish connection.
ip_internal — internal IP address of the remote machine, if provided. Otherwise, leave it out.

As Ansible works with SSH, it is required to exchange ssh-keys between the nodes, disable password authorization, and enable authorization by key. It is also necessary to enable root access without password.

Launch the playbook

Launch Let’s Kube with:

anisble-playbook bootstrap.yaml -i inventory -v

The -i flag refers to the inventory file that stores the data for connection. The
-v flag enables logging.

The cluster will now setup automatically.

Smoke test the cluster

Go to the m1 node and print nodes:

kubectl get nodes
NAME STATUS ROLES AGE VERSION
m1 Ready master 10m v1.9.7
s1 Ready <none> 10m v1.9.7

Print the pods and make sure that all K8s system pods are running:

kubectl get pods — all-namespaces

What you should see:

NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system calico-kube-controllers-846c7bf5ff-jb2r8 1/1 Running 0 10m
kube-system calico-node-qjvwm 2/2 Running 0 10m
kube-system calico-node-sgc9j 2/2 Running 0 10m
kube-system calico-node-zjf5f 2/2 Running 0 10m
kube-system kube-apiserver-k1 1/1 Running 0 10m
kube-system kube-controller-manager-k1 1/1 Running 0 10m
kube-system kube-dns-6f4fd4bdf-sj79m 3/3 Running 0 10m
kube-system kube-proxy-4nldc 1/1 Running 0 10m
kube-system kube-proxy-8qw66 1/1 Running 0 10m
kube-system kube-proxy-cllk2 1/1 Running 0 10m
kube-system kube-scheduler-k1 1/1 Running 0 10m

Now deploy an application and expose its port to make sure it’s accessible from the outside. Let’s launch nginx:

kubectl run nginx — image nginx

What you should see:

deployment “nginx” created

Check if the pod is launched:

kubectl get pods — all-namespaces

In case it’s launched, you will see:

NAMESPACE NAME READY STATUS RESTARTS AGE
default nginx-8586cf59-zjlrp 1/1 Running 0 12s

If you launch pods without specifying the namespace, they are launched in the default namespace by default.

Now expose the port:

kubectl expose deploy nginx — port 8080 — target-port 80

Get the IP address of the deployment:

kubectl get pods -o wide -n default

You should get the IP address:

NAME READY STATUS RESTARTS AGE IP NODE
nginx-8586cf59-zjlrp 1/1 Running 0 19m 10.244.99.38 s1

Check availability by curling the printed address:

curl 10.244.99.38:80

In case the test is succesful, nginx should return:

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
 body {
 width: 35em;
 margin: 0 auto;
 font-family: Tahoma, Verdana, Arial, sans-serif;
 }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and working. Further configuration is required.</p><p>For online documentation and support please refer to
<a href=”http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href=”http://nginx.com/">nginx.com</a>.</p><p><em>Thank you for using nginx.</em></p>
</body>
</html>

Congratulations! You’ve just bootstrapped a Kubernetes cluster with Let’s Kube. If you like the script, you can support the project by giving it a ⭐ on the official repository. Also follow us on Twitter and join our Telegram chat to stay tuned!

Please, feel free to leave feedback and ask questions.

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