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Provisioning a desktop Kubernetes cluster within VirtualBox with Packer and Vagrant

Build a single-machine Kubernetes cluster for local development purposes. Master and single node reside on the same VirtualBox VM. skydns is included in the cluster, so service lookup by name works.

Prerequisites

To proceed, you must have the following tools installed and on your PATH:

You will also need an executable kubectl toward the end of these instructions. Download a Kubernetes release tarball and extract kubectl from it.

Build

Build a base CentOS7 image and layer Kubernetes on top of it

sh build-all.sh

As part of its action, this script downloads the ISO image for CentOS7. The first time you run it may take 20-30 minutes, depending on your network. This ISO image is cached, so subsequent runs will take significantly less time.

Tweaking the Kubernetes configuration

Cluster configuration is easily modified by changing configs in kubernetes-configs/, followed by rebuilding the Kubernetes bits through Packer and Vagrant.

In kubernetes-configs/, config, apiserver, controller-manager, kubelet and proxy all map directly to systemd configs for the respective systemd Kubernetes services. apiserver.crt and apiserver.key are the TLS bits to secure the API master, and the yaml files are skydns config.

Persistent changes to the Kubernetes configuration do not require a full rebuild of the underlying CentOS box:

$ rm -rf artifacts/centos71-kubernetes box/virtualbox/centos71-kubernetes-x64-1.0.0.box
$ vagrant global-status | grep centos-7.1-x64 | awk '{print "vagrant destroy --force " $1}'  | sh
$ vagrant box remove --force centos71-kubernetes

$ packer build centos71-kubernetes-virtualbox.json

$ vagrant up --provider=virtualbox

Smoketesting the cluster

Smoke test the cluster by creating a trivial process in a busybox container, then exec into that container to do an nslookup on the Kubernetes system service.

sh smoketest.sh

When the cluster has settled, you should see this output from the nslookup command the smoketest launches

Every 2.0s: kubectl --kubeconfig=kubernetes-configs/kubeconfig exec busybox nslookup kubernetes        

Server:    192.168.0.53
Address 1: 192.168.0.53

Name:      kubernetes
Address 1: 192.168.0.1

Cleanup the smoketest busybox container

kubectl --kubeconfig=kubernetes-configs/kubeconfig delete pod busybox

Installing a capable kubeconfig

Here is the kubeconfig that lets you interact with this cluster without having to specify options to kubectl. Put this in $HOME/.kube/config:

apiVersion: v1
clusters:
- cluster:
    server: http://localhost:8080
  name: vbox
contexts:
- context:
    cluster: vbox
  name: vbox
current-context: vbox
kind: Config
preferences: {}

kubectl cluster-info
Kubernetes master is running at http://localhost:8080
KubeDNS is running at http://localhost:8080/api/v1/proxy/namespaces/kube-system/services/kube-dns