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Digital Ocean

In this tutorial, we'll create a Kubernetes v1.11.2 cluster on DigitalOcean with Container Linux.

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.

Controllers are provisioned to run an etcd-member peer and a kubelet service. Workers run just a kubelet service. A one-time bootkube bootstrap schedules the apiserver, scheduler, controller-manager, and coredns on controllers and schedules kube-proxy and flannel on every node. A generated kubeconfig provides kubectl access to the cluster.

Requirements

Digital Ocean Account and Token
Digital Ocean Domain (registered Domain Name or delegated subdomain)
Terraform v0.11.x and terraform-provider-ct installed locally

Terraform Setup

Install Terraform v0.11.x on your system.

$ terraform version
Terraform v0.11.7

Add the terraform-provider-ct plugin binary for your system.

wget https://github.com/coreos/terraform-provider-ct/releases/download/v0.2.1/terraform-provider-ct-v0.2.1-linux-amd64.tar.gz
tar xzf terraform-provider-ct-v0.2.1-linux-amd64.tar.gz
sudo mv terraform-provider-ct-v0.2.1-linux-amd64/terraform-provider-ct /usr/local/bin/

Add the plugin to your ~/.terraformrc.

providers {
  ct = "/usr/local/bin/terraform-provider-ct"
}

Read concepts to learn about Terraform, modules, and organizing resources. Change to your infrastructure repository (e.g. infra).

cd infra/clusters

Provider

Generate a Personal Access Token with read/write scope from the API tab. Write the token to a file that can be referenced in configs.

mkdir -p ~/.config/digital-ocean
echo "TOKEN" > ~/.config/digital-ocean/token

Configure the DigitalOcean provider to use your token in a providers.tf file.

provider "digitalocean" {
  version = "0.1.3"
  token = "${chomp(file("~/.config/digital-ocean/token"))}"
  alias = "default"
}

provider "local" {
  version = "~> 1.0"
  alias = "default"
}

provider "null" {
  version = "~> 1.0"
  alias = "default"
}

provider "template" {
  version = "~> 1.0"
  alias = "default"
}

provider "tls" {
  version = "~> 1.0"
  alias = "default"
}

Cluster

Define a Kubernetes cluster using the module digital-ocean/container-linux/kubernetes.

module "digital-ocean-nemo" {
  source = "git::https://github.com/poseidon/typhoon//digital-ocean/container-linux/kubernetes?ref=v1.11.2"
  
  providers = {
    digitalocean = "digitalocean.default"
    local = "local.default"
    null = "null.default"
    template = "template.default"
    tls = "tls.default"
  }

  # Digital Ocean
  cluster_name = "nemo"
  region       = "nyc3"
  dns_zone     = "digital-ocean.example.com"

  # configuration
  ssh_fingerprints = ["d7:9d:79:ae:56:32:73:79:95:88:e3:a2:ab:5d:45:e7"]
  asset_dir        = "/home/user/.secrets/clusters/nemo"
  
  # optional
  worker_count = 2
  worker_type  = "s-1vcpu-1gb"
}

Reference the variables docs or the variables.tf source.

ssh-agent

Initial bootstrapping requires bootkube.service be started on one controller node. Terraform uses ssh-agent to automate this step. Add your SSH private key to ssh-agent.

ssh-add ~/.ssh/id_rsa
ssh-add -L

Apply

Initialize the config directory if this is the first use with Terraform.

terraform init

Plan the resources to be created.

$ terraform plan
Plan: 54 to add, 0 to change, 0 to destroy.

Apply the changes to create the cluster.

$ terraform apply
module.digital-ocean-nemo.null_resource.bootkube-start: Still creating... (30s elapsed)
module.digital-ocean-nemo.null_resource.bootkube-start: Provisioning with 'remote-exec'...
...
module.digital-ocean-nemo.null_resource.bootkube-start: Still creating... (6m20s elapsed)
module.digital-ocean-nemo.null_resource.bootkube-start: Creation complete (ID: 7599298447329218468)

Apply complete! Resources: 54 added, 0 changed, 0 destroyed.

In 3-6 minutes, the Kubernetes cluster will be ready.

Verify

Install kubectl on your system. Use the generated kubeconfig credentials to access the Kubernetes cluster and list nodes.

$ export KUBECONFIG=/home/user/.secrets/clusters/nemo/auth/kubeconfig
$ kubectl get nodes
NAME             STATUS    AGE       VERSION
10.132.110.130   Ready     10m       v1.11.2
10.132.115.81    Ready     10m       v1.11.2
10.132.124.107   Ready     10m       v1.11.2

List the pods.

NAMESPACE     NAME                                       READY     STATUS    RESTARTS   AGE
kube-system   coredns-1187388186-ld1j7                   1/1       Running   0          11m
kube-system   kube-apiserver-n10qr                       1/1       Running   0          11m
kube-system   kube-controller-manager-3271970485-37gtw   1/1       Running   1          11m
kube-system   kube-controller-manager-3271970485-p52t5   1/1       Running   0          11m
kube-system   kube-flannel-1cq1v                         2/2       Running   0          11m
kube-system   kube-flannel-hq9t0                         2/2       Running   1          11m
kube-system   kube-flannel-v0g9w                         2/2       Running   0          11m
kube-system   kube-proxy-6kxjf                           1/1       Running   0          11m
kube-system   kube-proxy-fh3td                           1/1       Running   0          11m
kube-system   kube-proxy-k35rc                           1/1       Running   0          11m
kube-system   kube-scheduler-3895335239-2bc4c            1/1       Running   0          11m
kube-system   kube-scheduler-3895335239-b7q47            1/1       Running   1          11m
kube-system   pod-checkpointer-pr1lq                     1/1       Running   0          11m
kube-system   pod-checkpointer-pr1lq-10.132.115.81       1/1       Running   0          10m

Going Further

Learn about maintenance and addons.

!!! note 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.

Variables

Check the variables.tf source.

Required

Name	Description	Example
cluster_name	Unique cluster name (prepended to dns_zone)	nemo
region	Digital Ocean region	nyc1, sfo2, fra1, tor1
dns_zone	Digital Ocean domain (i.e. DNS zone)	do.example.com
ssh_fingerprints	SSH public key fingerprints	["d7:9d..."]
asset_dir	Path to a directory where generated assets should be placed (contains secrets)	/home/user/.secrets/nemo

DNS Zone

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.

resource "digitalocean_domain" "zone-for-clusters" {
  name       = "do.example.com"
  # Digital Ocean oddly requires an IP here. You may have to delete the A record it makes. :(
  ip_address = "8.8.8.8"
}

!!! tip "" 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.

SSH Fingerprints

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,

ssh-keygen -E md5 -lf ~/.ssh/id_rsa.pub | awk '{print $2}'
MD5:d7:9d:79:ae:56:32:73:79:95:88:e3:a2:ab:5d:45:e7

If you use ssh-agent (e.g. Yubikey for SSH), find the fingerprint with,

ssh-add -l -E md5
2048 MD5:d7:9d:79:ae:56:32:73:79:95:88:e3:a2:ab:5d:45:e7 cardno:000603633110 (RSA)

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.

Optional

Name	Description	Default	Example
controller_count	Number of controllers (i.e. masters)	1	1
worker_count	Number of workers	1	3
controller_type	Droplet type for controllers	s-2vcpu-2gb	s-2vcpu-2gb, s-2vcpu-4gb, s-4vcpu-8gb, ...
worker_type	Droplet type for workers	s-1vcpu-1gb	s-1vcpu-1gb, s-1vcpu-2gb, s-2vcpu-2gb, ...
image	Container Linux image for instances	"coreos-stable"	coreos-stable, coreos-beta, coreos-alpha
controller_clc_snippets	Controller Container Linux Config snippets	[]	example
worker_clc_snippets	Worker Container Linux Config snippets	[]	example
pod_cidr	CIDR IPv4 range to assign to Kubernetes pods	"10.2.0.0/16"	"10.22.0.0/16"
service_cidr	CIDR IPv4 range to assign to Kubernetes services	"10.3.0.0/16"	"10.3.0.0/24"
cluster_domain_suffix	FQDN suffix for Kubernetes services answered by coredns.	"cluster.local"	"k8s.example.com"

Check the list of valid droplet types or use doctl compute size list.

!!! warning Do not choose a controller_type smaller than 2GB. Smaller droplets are not sufficient for running a controller and bootstrapping will fail.

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