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Digital Ocean

In this tutorial, we'll create a Kubernetes v1.8.1 cluster on Digital Ocean.

We'll declare a Kubernetes cluster in Terraform using the Typhoon Terraform module. On apply, firewall rules, DNS records, tags, and droplets for Kubernetes controllers and workers will be created.

Controllers and workers are provisioned to run a kubelet. A one-time bootkube bootstrap schedules an apiserver, scheduler, controller-manager, and kube-dns on controllers and runs kube-proxy and flannel on each 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 v0.10.1+ and terraform-provider-ct installed locally

Terraform Setup

Install Terraform v0.10.1+ on your system.

$ terraform version
Terraform v0.10.1

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

wget https://github.com/coreos/terraform-provider-ct/releases/download/v0.2.0/terraform-provider-ct-v0.2.0-linux-amd64.tar.gz
tar xzf terraform-provider-ct-v0.2.0-linux-amd64.tar.gz
sudo mv terraform-provider-ct-v0.2.0-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

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

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"

  region   = "nyc3"
  dns_zone = "digital-ocean.example.com"

  cluster_name     = "nemo"
  image            = "coreos-stable"
  controller_count = 1
  controller_type  = "2gb"
  worker_count     = 2
  worker_type      = "512mb"
  ssh_fingerprints = ["d7:9d:79:ae:56:32:73:79:95:88:e3:a2:ab:5d:45:e7"]

  # output assets dir
  asset_dir = "/home/user/.secrets/clusters/nemo"
}

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

!!! warning terrafrom apply will hang connecting to a controller if ssh-agent does not contain the SSH key.

Apply

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

terraform init

Get or update Terraform modules.

$ terraform get            # downloads missing modules
$ terraform get --update   # updates all modules
Get: git::https://github.com/poseidon/typhoon (update)
Get: git::https://github.com/poseidon/bootkube-terraform.git?ref=v0.7.0 (update)

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.

$ KUBECONFIG=/home/user/.secrets/clusters/nemo/auth/kubeconfig
$ kubectl get nodes
NAME             STATUS    AGE       VERSION
10.132.110.130   Ready     10m       v1.8.1+coreos.0
10.132.115.81    Ready     10m       v1.8.1+coreos.0
10.132.124.107   Ready     10m       v1.8.1+coreos.0

List the pods.

NAMESPACE     NAME                                       READY     STATUS    RESTARTS   AGE
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-dns-1187388186-ld1j7                  3/3       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 version pinning, maintenance, and addons.

!!! note On Container Linux clusters, install the container-linux-update-operator addon to coordinate reboots and drains when nodes auto-update. Otherwise, updates may not be applied until the next reboot.

Variables

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. In this example, the cluster's apiserver would be accessible at nemo.do.example.com.

You'll need a registered domain name or subdomain registered in Digital Ocean Domains (i.e. DNS zones). You can set this up once and create many clusters with unqiue 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 carve out 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 -lf ~/.ssh/id_rsa.pub | awk '{print $2}'
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)

If you uploaded an SSH key to DigitalOcean (not required), find the fingerprint under Settings -> Security. Finally, if you don't have an SSH key, create one now.

Optional

Name Description Default Example
image OS image for droplets "coreos-stable" coreos-stable, coreos-beta, coreos-alpha
controller_count Number of controllers (i.e. masters) 1 1
controller_type Digital Ocean droplet size 2gb 2gb (min), 4gb, 8gb
worker_count Number of workers 1 3
worker_type Digital Ocean droplet size 512mb 512mb, 1gb, 2gb, 4gb
networking Choice of networking provider "flannel" "flannel"
pod_cidr CIDR range to assign to Kubernetes pods "10.2.0.0/16" "10.22.0.0/16"
service_cidr CIDR range to assgin to Kubernetes services "10.3.0.0/16" "10.3.0.0/24"

!!! warning Do not choose a controller_type smaller than 2gb. The 1gb droplet is not sufficient for running a controller and bootstrapping will fail.

!!! bug Digital Ocean firewalls do not yet support the IP tunneling (IP in IP) protocol used by Calico. You can try using "calico" for networking, but it will only work if the cloud firewall is removed (unsafe).