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My NixOS K3S Cluster

My NixOS based K3S Cluster fully declarative and reproducable from empty disk to operating services, hosted on my personal Git Server. Feel free to look around. Be aware that not all configuration files are available in my public repository.

Overview

This repository provides the Infrastructure as Code (IaC) and GitOps State with the following core components:

  • NixOS: Linux distribution based on Nix to provide a declarative and reproducible (flakes) system.
  • K3S: Lightweight certified Kubernetes distribution.
  • Flux: GitOps Kubernetes Operator that ensures that my cluster state matches the desired state described in this repository.
  • Renovate: Automatically updates dependencies declared in my Git repository via pull requests.
  • SOPS: Tool for managing secrets.
  • Cilium: eBPF-based Networking, Observability and Security (CNI, LB, Network Policy, etc.).
  • Cert-Manager: Cloud native certificate management.
  • Gitea: Self-hosted Git Server.

Description

A single node k3s cluster which can be fully reproducibly deployed with a single command. At the same time the node contains the git server which represents the GitOps state of the cluster. To solve the chicken edge problem an additional git server is configured on operating system level which serves the infra repositories to have the cluster configurable even in case of configuration errors. For backup purpose i recommend to setup a mirror of the infra repositories inside the k3s git server to use the config driven k3s backup methods. While a local Git server is not required, I prefer to keep the entire stack under my own control.

In contrast to most public nixos system repositories, i use a separate nixos module repository and not a monorepository with all my systems. Since my systems have highly different release and update cycles, this makes it much easier to manage different system version states. A partial mirror of my nixos modules is available at niki-on-github/nixos-modules.

Setup

Install

Boot any linux iso (recomended is nixos minimal) on your server and run the following command on your local computer:

nix run '.#install-system' -- supermicro-k3s root@${IP}

Depending on the chosen linux iso you may have to set the root user password and enable the ssh server to make the server accessable via ssh. The command above is a wrapped script which fetches the encryption keys from my local hosted vault and use nixos-anywhere to deploy the system.

Note

On my supermicro board i can not boot the official nixos minimal iso. Selecting an enty in the live iso grub menu result in loading the default boot device. Workaround is to boot an arch linux iso and use the command from above, which automatically uses kexec to load nixos setup. Due to the storage limit we first have to execute mount -o remount,size=2G /run/archiso/cowspace on the arch linux live iso.

Update (System)

This is only necessarry when the NixOS system configuration in this repository has changed. All configuration insied the ./kubernetes directory will automaticaly applied by Flux and don't need manuall interaction with the cluster.

nix run '.#update-system' -- supermicro-k3s ${IP}

Fix Faulty Configuration

git remote add fallback http://${ip}:3000/r/nixos-k3s.git
git pull fallback main
# make required changes ...
git push fallback

Use branch protection in gitea for the recovery process to prevent force push to faulty config state when gitea recovery is applied in k3s.

Checklist

  • Branch Protection is activated on nixos gitea service until the recovery process is completed
  • Set spec.paused=true in ./kubernetes/templates/volsync-pvc/replication-source.yaml