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Kubernetes (k3s) Terraform installer for Hetzner Cloud

This Terraform module creates a Kubernetes Cluster on Hetzner Cloud infrastructure running Ubuntu 20.04. The cluster is designed to take advantage of the Hetzner private network, and is equiped with Hetzner specific cluster enhancements.

Cluster size and instance types are configurable through Terraform variables.

Install

Prerequisites

  • Terraform must be installed
  • Bash must be installed
  • SSH should be installed and configured with an SSH Key and Agent (Recommended)
  • Having kubectl installed is recommended

Note that you'll need Terraform v0.12 or newer to run this project.

Hetzner Cloud API Token

Before running the project you'll have to create an access token for Terraform to connect to the Hetzner Cloud API.

read -sp "Hetzner Cloud API Token: " TF_VAR_hcloud_token # Enter your Hetzner Cloud API Token (it will be hidden)
export TF_VAR_hcloud_token

Usage

Create a main.tf file in a new directory with the following contents:

variable "hcloud_token" {
  type = string
}

provider "hcloud" {
  token = var.hcloud_token
}

# Create a new SSH key
resource "hcloud_ssh_key" "default" {
  name = "Terraform Example"
  public_key = file("~/.ssh/id_rsa.pub")
}

module "cluster" {
  source  = "cicdteam/k3s/hcloud"
  version = "0.1.2"
  hcloud_token = var.hcloud_token
  ssh_keys = [hcloud_ssh_key.default.id]
}

output "master_ipv4" {
  depends_on  = [module.cluster]
  description = "Public IP Address of the master node"
  value       = module.cluster.master_ipv4
}

output "nodes_ipv4" {
  depends_on  = [module.cluster]
  description = "Public IP Address of the worker nodes"
  value       = module.cluster.nodes_ipv4
}

That's all it takes to get started!

Pin to a specific module version using version = "..." to avoid upgrading to a version with breaking changes. Upgrades to this module could potentially replace all master and worker nodes resulting in data loss. The terraform plan will report this, but it may not be obvious.

Create an Hetzner Cloud Kubernetes cluster with one master and a node:

terraform apply

This will do the following:

  • provisions Hetzner Cloud Instances with Ubuntu 20.04 (the instance type/size of the master and the node may be different)
  • installs K3S components and supporting binaries
  • joins the nodes in the cluster
    • installs Hetzner Cloud add-ons:
      • CSI (Container Storage Interface driver for Hetzner Cloud Volumes)
      • CCM (Kubernetes cloud-controller-manager for Hetzner Cloud)
  • creates two bash scripts to setup/destroy new context in the kubectl admin config file for local kubectl

After applying the Terraform plan you'll see several output variables like the master public IP and nodes IPs.

terraform destroy -force

Be sure to clean-up any CSI created Block Storage Volumes, and CCM created NodeBalancers that you no longer require.

Addons Included

Hetzner Cloud cloud controller manager (CCM)

The Hetzner Cloud cloud controller manager integrates your Kubernets cluster with the Hetzner Cloud API. Read more about kubernetes cloud controller managers in the kubernetes documentation.

Features

  • instances interface: adds the server type to the beta.kubernetes.io/instance-type label, sets the external ipv4 and ipv6 addresses and deletes nodes from Kubernetes that were deleted from the Hetzner Cloud.
  • zones interface: makes Kubernetes aware of the failure domain of the server by setting the failure-domain.beta.kubernetes.io/region and failure-domain.beta.kubernetes.io/zone labels on the node.
  • Private Networks: allows to use Hetzner Cloud Private Networks for your pods traffic.
  • Load Balancers: allows to use Hetzner Cloud Load Balancers with Kubernetes Services

Container Storage Interface driver for Hetzner Cloud (CSI)

This is a Container Storage Interface driver for Hetzner Cloud enabling you to use Volumes within Kubernetes.

When a PV is deleted, the Hetzner Block Storage Volume will be deleted as well, based on the ReclaimPolicy.

Learn More about Persistent Volumes on kubernetes.io.