nixos-servers

Nix definitions to configure our servers at home.

Acknowledgements

• deploy-rs: NixOS deploy tool with rollback functionality
• disko: declarative disk partitioning
• dns.nix: A Nix DSL for defining DNS zones
• flake-utils: Handy utilities to develop Nix flakes
• nixos-hardware: Hardware-specific NixOS modules. Doing the heavy lifting for our Raspberry Pi
• kubenix: declare and deploy Kubernetes resources using Nix
• nixhelm: Nix-digestible Helm charts
• sops-nix: Sops secret management for Nix

Installation

Prerequisites

1. Install the Nix package manager or NixOS (link)
2. Enable flake and nix commands (link)

Bootstrapping

We bootstrap our servers using nixos-anywhere. This reformats the hard disk of the server and installs a fresh NixOS. Additionally, it deploys an age identity, which is later used for decrypting secrets.

⚠️ This will wipe your server completely ⚠️

1. Make sure your have a Secret service running (such as Keepassxc) that provides the age identity.
2. Ensure you have root SSH access to the server.
3. Run nixos-anywhere: nix run '.#bootstrap' <servername> <hostname>

Deployment

To deploy all servers at once: nix run 'nixpkgs#deploy-rs' -- '.#' -k To deploy only one server: nix run 'nixpkgs#deploy-rs' -- -k --targets '.#<host>'

Deploying to Kubernetes

To deploy to the Kubernetes cluster, first make sure you have an admin account on the cluster. You can generate this using nix run '.#gen-k3s-cert' <username> <servername> ~/.kube, assuming you have SSH access to the master node. This puts a private key, signed certificate and a kubeconfig in the kubeconfig directory

We are now ready to deploy to the Kubernetes cluster. Deployments are done through an experimental Kubernetes feature called ApplySets. Each applyset is responsible for a set number of resources within a namespace.

If the cluster has not been initialized yet, we must bootstrap it first. Run these deployments:

• nix run '.#bootstrap-default'
• nix run '.#bootstrap-kube-system'

Now the cluster has been initialized and we can deploy applications. To explore which applications we can deploy, run nix flake show. Then, for each application, run nix run '.#<application>'.

Known bugs

Rsync not available during bootstrap

The rsync command was removed from recent NixOS ISO which causes nixos-anywhere to fail when copying extra files. See this issue. Solution is to execute nix-env -iA nixos.rsync on the host.