A Simple OpenTofu and k3d Workflow

I use k3d to run local experiments. I recently streamlined the configuration and figured I would share the setup code and figured I would share the basic workflow.

Why?

k3d is a lightweight kubernetes distribution based on docker. With docker, I can isolate all the packages needed for a particular application. The benefit is twofold:

Reproducability
Package management

I can create a docker container for a particular experiment. If I'm no longer interested, I can simply delete the docker image and I can remove all the clutter associated with the project. If I need to move the codebase to a seperate machine, I have all the steps needed to reproduce the working code in the docker container. Now lets move on to the code.

Install Dependencies

First, follow this guide to install k3d on your machine. Make sure you also install opentofu, which is an open source variant of terraform.

Create Docker Registry

Now we have to have a place to register custom docker images. The simplest setup for me is to use k3d to manage a local registry:

k3d registry create myregistry.localhost --port 45777

Where myregistry can be any name for the docker registry and 45777 is any free port on the host machine.

Create k3d Cluster

Now we can create k3d cluster and point it to the local docker registry. I also mount a volume that contains the code for all my projects. This makes it easy to hot-reload changes versus packaging the application code directly in the docker container. You can find a list of all the command line flags here

k3d cluster create
  --registry-use k3d-myregistry.localhost:45777
  --volume /home/david/pkg:/pkg
  --port "8000:80@loadbalancer"
  mycluster

We will also need the kubernetes configuration created by k3d so that we can access the kubernetes API with opentofu. It is enough to write this data to a file and read it back in opentofu:

k3d kubeconfig write maestro -o kubeconfig

OpenTofu Setup

Now we can create the standard main.tf file used in all opentofu projects:

# main.tf

# specify the kubernetes provider
terraform {
    required_providers {
        kubernetes = {
            source = "hashicorp/kubernetes"
            version = "2.11.0"
        }
    }
}

# use configuration created by k3d
# we should have already written the config to filesystem
provider "kubernetes" {
  config_path = "${path.module}/kubeconfig"
}

Now we just initialize opentofu and apply the changes like we normally would:

tofu init
tofu apply

Fin

This is the basic setup to get opentofu talking to a k3d cluster. From here you can customize main.tf to include any specific changes that your cluster requires. I plan to do a future article where I go into depth streamlining any friction points. Happy hacking!