Author here. It's mainly for k8s resources; but if you install operators like external-dns or something like crossplane into your cluster, you can manage infra too.
What alternative to terraform would one use to set up the whole cluster before provisioning any resources?
I currently have a custom script that is a mix between terraform and ansible that sets up a proxmox cluster, then a k3s cluster and a few haproxys with keepalived on top. Granted, maybe not the most standard setup.
Do you have a complex Ansible setup? For the few bespoke VMs I need, I've been able to get away with cloud init so far - but they're explicitly set up to be reasonable to nuke and recreate - if they had more personality and needed to be more managed as pets - I would probably need to reach for something like Ansible - or see if I could build images (vm or Docker).
But then with images I'm on the hook for patching... Not simply auto-patching via apt...
I use the cluster-api provider for Proxmox running in an ephemeral cluster (usually kind) to bootstrap the Kubernetes cluster to a point where Flux gets installed and it takes over managing itself. I then throw the kind cluster away as I no longer need it.
I've considered dropping terraform (openTofu) for our k8s resources since k8s is stateful anyway.
But that would complicate synchronization with resources outside of k8s, like tailscale, DNS, managed databases, cloud storage (S3 compatible) - and even mapping k8s ingress to load_balancer and external DNS.
So far I feel that everything in terraform is the most simple and reasonable solution - mostly because everything can be handled by a single tool and language.
Consider CDK8s (Typescript or Go) or Jsonnet. We evaluated Cue and the two aforementioned options and ended up with CDK8s using Typescript and it's incredibly powerful.
