Kubernetes installation with kubeadm

In my previous post, I presented an easy way how to deploy Kubernetes cluster with Rancher. Kubernetes is hard to install without using third party tools, but luckily they released an official tool for simple deployment kubeadm. Please note that kubeadm is still in Alpha and not ready for production use, but it is good enough to play with on development environments. Kubernetes installation with kubeadm really simplifies deployment procedure and it is easy to use. Also, I find it very stable during my testing. kubeadm is a part of Kubernetes distribution starting with 1.4.0 release, but it does not track same release process at the moment. I’m expecting it to be ready for Kubernetes 1.6.

In this post, I will show you how to use kubeadm tool and some tips for installing Kubernetes on Vagrant environment. Everything is done manually for a better understanding of the process, but it could be easily automated with some configuration management tool like SaltStack. Here is Vagrantfile I used to run 3 VMs:

I also added additional network interface for Kubernetes cluster networking and a simple shell command to update hosts file during provisioning. This is required by Kubernetes networking to work when running on Vagrant because the first interface is NAT bridge and all nodes have the same IP address. After all VMs are up and running the first step is to add official Kubernetes repo and to install all required packages:

Repeat above step on all three VMs. When installed we can start cluster initialization on the master node:

A short explanation for all three command parameters:

  • --api-advertise-addresses to select which interface to use
  • --pod-network-cidr is required for flannel network
  • --token 8c2350.f55343444a6ffc46 if omitted token will be auto-generated

A note from official docs on networking with kubeadm:

You must install a pod network add-on so that your pods can communicate with each other. It is necessary to do this before you try to deploy any applications to your cluster, and before kube-dns will start up. Note also that kubeadm only supports CNI based networks and therefore kubenet based networks will not work.

Flannel networking without Etcd

In this example, I will use Flannel experimental feature to use Kubernetes API as a datastore instead of Etcd. Options used to start Flannel containers:

--iface=enp0s8 parameter is required if you have multiple NICs. Also, I added KUBERNETES_SERVICE_HOST= and KUBERNETES_SERVICE_PORT=6443 environment variables for flannel to be able to reach Kubernetes API. Otherwise flannel will try to reach Kubernetes API at, which for some reason is not accessible from agents. I’m not quite sure if this is a bug.

Now download and start Flannel network CNI:

After some time you should see all services running. Also DNS service should be running at this point:

Adding Kubernetes nodes

Adding a new Kubernetes node is easy. Just one command:

After a few minutes you should see that node is in ready state:

Adding Kubernetes dashboard

Run below command to start Kubernetes dashboard service:

Accessing Kubernetes dashboard or any other service from your localhost is easy. You just need to find NodePort of the service and to create forward rule on VirtualBox. Find NodePort for kubernetes-dashboard service:

An easy way to create a forward rule is with VBoxManage cli tool. List all running VMs:

Forward port 31531 from the above command to your localhost on port 9090. The rule can be created on any agent:

At this point you should be able to access Kubernetes dashboard on http://localhost:9090

If you have any questions please leave a comment. Also please check the limitations of kubeadm tool.

Updates with kubernetes v1.6.1:

kubeadm is in beta now and some commands have changed.

Cluster initialization:

You will also get the message:
Flannel RBAC:
Flannel config:
To join the agents you need to specify a port also:
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Alen Komljen

Building and automating infrastructure with Docker, Kubernetes, kops, Helm, Rancher, Terraform, Ansible, SaltStack, Jenkins, AWS, GKE and many others.
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