Integrating DigitalOcean Cloud Controller with k0s in Your Kubernetes Cluster: A Guide

August 7, 2023

An image showing a computer cluster with multiple servers stacked in a data center. The image is intended to be the main graphic for a Medium article about Kubernetes.

Running your own Kubernetes cluster offers several advantages like more control over your environment, enhanced privacy and security, and the adaptability to tweak the cluster according to your requirements. On top of that it is also cheaper than a managed cluster.

k0s is a great tool to quickly setup Kubernetes clusters. If you combine it with a Cloud Controller Manager (CCM) it really makes life easier since Load Balancer and storage are automatically set up just like with a managed cluster. A Load Balancer is needed e.g. if you would like to use an Ingress Controller. An Ingress Controller is able to manage and direct external traffic to services within a Kubernetes cluster, which can then route the traffic to the appropriate pods.

Initially I wanted to use k3s and even found an outdated k3s tutorial but k3s kept producing weird errors e.g. when I tried to access the pod logs. With k0s I did not have any problems at all. That is why I created this guide and when faced with the challenge of choosing between k0s vs k3s, I will chose k0s.

This guide will walk you through the steps to establish a self-governed, single-node Kubernetes cluster on a DigitalOcean droplet with k0s, augmented with the capabilities of the DigitalOcean Cloud Controller Manager and Traefik Ingress Controller.

Prerequisites:

A DigitalOcean account and API token. If you use my referral link and spend more than 25$ on DigitalOcean, I will receive 25$.
A droplet configured on DigitalOcean. I recommend Ubuntu.
Access to the droplet via DigitalOcean console or SSH.
Swap file with 4GB and swappiness of 60

Step-by-Step Guide:

1. Connect to Your Droplet

Option 1: SSH

Use SSH to access your DigitalOcean droplet:

ssh -i /path/to/your/private/key root@<droplet-ip-address>

Replace /path/to/your/private/key with your private key file path and <droplet-ip-address> with your droplet's IP.

Option 2: DigitalOcean Console

Alternatively, utilize the built-in console by DigitalOcean. Head to the “Droplets” section in your DigitalOcean dashboard, select the droplet you wish to access, and click on “Console”.

2. Download k0s

Begin by downloading k0s, a compact, single-binary Kubernetes distribution:

curl -sSLf https://get.k0s.sh | sudo sh

3. Retrieve Your Droplet ID

To set the Droplet ID for the Kubernetes node, fetch the Droplet ID using DigitalOcean’s metadata service. The following command will store the ID in a variable called DROPLET_ID:

DROPLET_ID=$(curl http://169.254.169.254/metadata/v1/id)

4. Install and Start the k0s Controller

Install the k0s controller on the node by executing the next command. We do not need to make any changes to it since we stored the the Droplet ID in the variable DROPLET_ID:

k0s install controller --single --enable-cloud-provider=true --kubelet-extra-args="--provider-id=digitalocean://$DROPLET_ID"

k0s start

Ensure the correctness of your setup by running k0s status, which should display the status of your Kubernetes cluster.

5. Create a Kubernetes Secret for the DigitalOcean API Token

Create a secret in the kube-system namespace to store the DigitalOcean API token. Please replace digitalocean-api-token with your API token:

k0s kubectl -n kube-system create secret generic digitalocean --from-literal=access-token=digitalocean-api-token

6. Install the DigitalOcean Cloud Controller Manager

The DigitalOcean Cloud Controller Manager (CCM) facilitates nodes in discovering their droplet details and also supports services of type LoadBalancer:

k0s kubectl apply -f https://raw.githubusercontent.com/digitalocean/digitalocean-cloud-controller-manager/master/releases/v0.1.43.yml

7. Install the Helm Package Manager

Initially I had used the NGINX Ingress Controller but I turned out to be unreliable regarding websockets. Sometimes it forwarded websockets, sometimes it did not. I decided to use the Traefik Ingress Controller which turned out to be very reliable. To do so, one needs to install Helm first. Helm is a package manager for Kubernetes.

curl -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3

chmod 700 get_helm.sh

./get_helm.sh

8. Install kubectl

Install kubectl by following this guide. I would recommend to do it via apt.

Add the export line to ~/.bashrc via the following command:

echo 'export KUBECONFIG=/var/lib/k0s/pki/admin.conf' >> ~/.bashrc

Run the following command to apply the changes in the current terminal:

source ~/.bashrc

9. Install the Traefik Ingress Controller

Conclude by installing the Traefik Ingress Controller to oversee inbound traffic routing:

helm repo add traefik https://helm.traefik.io/traefik

helm repo update

helm install traefik traefik/traefik

Check if Traefik is part of the list when executing the command k0s kubectl get pods. If that is the case, check your DigitalOcean dashboard to verify that the Traefik Ingress Controller has successfully instantiated a Load Balancer.

10. Firewall Setup

Last but not least, we need to click on the Load Balancer Edit settings button in the DigitalOcean Dashboard to check to which ports on our droplet the Load Balancer forwards traffic (first click on the three dots to the right of the Load Balancer). You will see forwarding rules which may look similar to these:

TCP on port 80  TCP on port 30642

TCP on port 443 TCP on port 32608

Open the ports on the right (differ in every setup) in the Firewall settings which can be accessed via the Networking button.

Wrapping Up:

Kudos! You’ve adeptly set up a self-governed, single-node Kubernetes cluster on a DigitalOcean droplet with k0s, complemented by the DigitalOcean Cloud Controller Manager and the Traefik Ingress Controller.

This environment offers the perks of a self-managed Kubernetes cluster, such as heightened control, privacy, security, and customization, all while integrating effortlessly with DigitalOcean’s Load Balancers. This lets you effortlessly expose your software to the web.

Whether you’re in the phases of testing, development, or deployment, this setup ensures a sturdy and adaptable backdrop for your projects. Wishing you fruitful deployments!