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DigitalOcean

In this tutorial, we'll create a Kubernetes v1.18.4 cluster on DigitalOcean with CoreOS Container Linux or Flatcar 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.

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.

Requirements

  • Digital Ocean Account and Token
  • Digital Ocean Domain (registered Domain Name or delegated subdomain)
  • Terraform v0.12.6+ and terraform-provider-ct installed locally

Terraform Setup

Install Terraform v0.12.6+ on your system.

$ terraform version
Terraform v0.12.21

Add the terraform-provider-ct plugin binary for your system to ~/.terraform.d/plugins/, noting the final name.

wget https://github.com/poseidon/terraform-provider-ct/releases/download/v0.5.0/terraform-provider-ct-v0.5.0-linux-amd64.tar.gz
tar xzf terraform-provider-ct-v0.5.0-linux-amd64.tar.gz
mv terraform-provider-ct-v0.5.0-linux-amd64/terraform-provider-ct ~/.terraform.d/plugins/terraform-provider-ct_v0.5.0

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

cd infra/clusters

Provider

Login to DigitalOcean or create an account, if you don't have one.

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 = "1.20.0"
  token = "${chomp(file("~/.config/digital-ocean/token"))}"
}

provider "ct" {
  version = "0.5.0"
}

Flatcar Linux Images

Flatcar Linux publishes DigitalOcean images, but does not yet upload them. DigitalOcean allows custom images to be uploaded via URLor file.

Download the Flatcar Linux DigitalOcean bin image. Rename the image with the channel and version (to refer to these images over time) and upload it as a custom image.

data "digitalocean_image" "flatcar-stable-2303-4-0" {
  name = "flatcar-stable-2303.4.0.bin.bz2"
}

Set the os_image in the next step.

Cluster

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

module "nemo" {
  source = "git::https://github.com/poseidon/typhoon//digital-ocean/container-linux/kubernetes?ref=v1.18.4"

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

  # configuration
  os_image         = data.digitalocean_image.flatcar-stable-2303-4-0.id
  ssh_fingerprints = ["d7:9d:79:ae:56:32:73:79:95:88:e3:a2:ab:5d:45:e7"]

  # optional
  worker_count = 2
}

Reference the variables docs or the variables.tf source.

ssh-agent

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.

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.nemo.null_resource.bootstrap: Still creating... (30s elapsed)
module.nemo.null_resource.bootstrap: Provisioning with 'remote-exec'...
...
module.nemo.null_resource.bootstrap: Still creating... (6m20s elapsed)
module.nemo.null_resource.bootstrap: Creation complete (ID: 7599298447329218468)

Apply complete! Resources: 42 added, 0 changed, 0 destroyed.

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

Verify

Install kubectl on your system. Obtain the generated cluster kubeconfig from module outputs (e.g. write to a local file).

resource "local_file" "kubeconfig-nemo" {
  content  = module.nemo.kubeconfig-admin
  filename = "/home/user/.kube/configs/nemo-config"
}

List nodes in the cluster.

$ export KUBECONFIG=/home/user/.kube/configs/nemo-config
$ kubectl get nodes
NAME               STATUS  ROLES   AGE  VERSION
10.132.110.130     Ready   <none>  10m  v1.18.4
10.132.115.81      Ready   <none>  10m  v1.18.4
10.132.124.107     Ready   <none>  10m  v1.18.4

List the pods.

NAMESPACE     NAME                                       READY     STATUS    RESTARTS   AGE
kube-system   coredns-1187388186-ld1j7                   1/1       Running   0          11m
kube-system   coredns-1187388186-rdhf7                   1/1       Running   0          11m
kube-system   calico-node-1m5bf                          2/2       Running   0          11m
kube-system   calico-node-7jmr1                          2/2       Running   0          11m
kube-system   calico-node-bknc8                          2/2       Running   0          11m
kube-system   kube-apiserver-ip-10.132.115.81            1/1       Running   0          11m
kube-system   kube-controller-manager-ip-10.132.115.81   1/1       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-ip-10.132.115.81            1/1       Running   0          11m

Going Further

Learn about maintenance and addons.

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"
os_image Container Linux image for instances "custom-image-id", coreos-stable, coreos-beta, coreos-alpha
ssh_fingerprints SSH public key fingerprints ["d7:9d..."]

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 DigitalOcean Domains (i.e. DNS zones). You can set this up once and create many clusters with unique names.

# Declare a DigitalOcean record to also create a zone file
resource "digitalocean_domain" "zone-for-clusters" {
  name       = "do.example.com"
  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-2gb" s-1vcpu-2gb, s-2vcpu-2gb, ...
controller_snippets Controller Container Linux Config snippets [] example
worker_snippets Worker Container Linux Config snippets [] example
networking Choice of networking provider "calico" "flannel" or "calico"
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"

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.