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.
Add the [terraform-provider-ct](https://github.com/poseidon/terraform-provider-ct) plugin binary for your system to `~/.terraform.d/plugins/`, noting the final name.
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.
Reference the [variables docs](#variables) or the [variables.tf](https://github.com/poseidon/typhoon/blob/master/digital-ocean/container-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. Use the generated `kubeconfig` credentials to access the Kubernetes cluster and list nodes.
On Container Linux clusters, install the `CLUO` addon to coordinate reboots and drains when nodes auto-update. Otherwise, updates may not be applied until the next reboot.
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 Digital Ocean 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`.
