We'll declare a Kubernetes cluster using the Typhoon Terraform module. Then apply the changes to create controller droplets, worker droplets, DNS records, tags, and TLS assets.
Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and `calico` (or `flannel`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
Read [concepts](/architecture/concepts/) to learn about Terraform, modules, and organizing resources. Change to your infrastructure repository (e.g. `infra`).
Login to [DigitalOcean](https://cloud.digitalocean.com) or create an [account](https://cloud.digitalocean.com/registrations/new), if you don't have one.
Generate a Personal Access Token with read/write scope from the [API tab](https://cloud.digitalocean.com/settings/api/tokens). Write the token to a file that can be referenced in configs.
```sh
mkdir -p ~/.config/digital-ocean
echo "TOKEN" > ~/.config/digital-ocean/token
```
Configure the DigitalOcean provider to use your token in a `providers.tf` file.
Flatcar Linux publishes DigitalOcean images, but does not yet upload them. DigitalOcean allows [custom images](https://blog.digitalocean.com/custom-images/) to be uploaded via URLor file.
[Download](https://www.flatcar-linux.org/releases/) the Flatcar Linux DigitalOcean bin image. Rename the image with the channel and version (to refer to these images over time) and [upload](https://cloud.digitalocean.com/images/custom_images) it as a custom image.
```tf
data "digitalocean_image" "flatcar-stable-2303-4-0" {
Reference the [variables docs](#variables) or the [variables.tf](https://github.com/poseidon/typhoon/blob/master/digital-ocean/flatcar-linux/kubernetes/variables.tf) source.
Initial bootstrapping requires `bootstrap.service` be started on one controller node. Terraform uses `ssh-agent` to automate this step. Add your SSH private key to `ssh-agent`.
[Install kubectl](https://kubernetes.io/docs/tasks/tools/install-kubectl/) on your system. Obtain the generated cluster `kubeconfig` from module outputs (e.g. write to a local file).
Clusters create DNS A records `${cluster_name}.${dns_zone}` to resolve to controller droplets (round robin). This FQDN is used by workers and `kubectl` to access the apiserver(s). In this example, the cluster's apiserver would be accessible at `nemo.do.example.com`.
You'll need a registered domain name or delegated subdomain in DigitalOcean Domains (i.e. DNS zones). You can set this up once and create many clusters with unique names.
If you have an existing domain name with a zone file elsewhere, just delegate a subdomain that can be managed on DigitalOcean (e.g. do.mydomain.com) and [update nameservers](https://www.digitalocean.com/community/tutorials/how-to-set-up-a-host-name-with-digitalocean).
DigitalOcean droplets are created with your SSH public key "fingerprint" (i.e. MD5 hash) to allow access. If your SSH public key is at `~/.ssh/id_rsa`, find the fingerprint with,
Digital Ocean requires the SSH public key be uploaded to your account, so you may also find the fingerprint under Settings -> Security. Finally, if you don't have an SSH key, [create one now](https://help.github.com/articles/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent/).
Check the list of valid [droplet types](https://developers.digitalocean.com/documentation/changelog/api-v2/new-size-slugs-for-droplet-plan-changes/) or use `doctl compute size list`.
