alpine k0s cluster with terraform and libvirt

My development cluster with libvirt and terraform

Prerequisites

• libvirt with qemu
• terraform
• terraform-provider-libvirt
• alpine-make-vm-image
• k0sctl

alpine-make-vm-image needs root permissions. Currently doas is used for this.

User should be in libvirt group.

The libvirt network default is used. It is assumed that the DNS server for this is listening on 192.168.122.1.

The ssh key $HOME/.ssh/id_ed25519 is used for root logins. If this is password protected you should add the key with:

eval $(ssh-add ~/.ssh/id_ed25519)

How to configure the cluster

The file variables.tf has some variables for the cluster:

variable	explanation
memory	amount of RAM (in megabytes) for ach virtual machine.
vcpu	number of virtual CPUs for each virtual machine.
controller_nodes	number of controllers in the kubernetes cluster
worker_nodes	number of workers for the controller node

How to build the cluster

Run make. This will:

1. build vm-image/alpine-cloud.img
2. use terraform apply to spin up the virtual machines and feed them with a seed.iso image with cloud-init config (currently only hostname is set)
3. generate a nodelist.txt with the list of virtual machines hostnames
4. use dig to query the 192.168.122.1 DNS server for the ip address of the virtual machines.
5. generate a k0sctl.yaml config with the list of IP addresses.
6. execute k0sctl to spin up the cluster
7. generate a kubeconfig file for kubectl or Lens.

How to connect to the kubernetes cluster

To use the generated kubeconfig run:

export KUBECONFIG=$PWD/kubeconfig

Now you can connect to the cluster with kubectl:

kubectl get nodes