randogoth d1321cf7ca docs: nixos-26.05 in adopt examples, document impermanence

Bump the wrapper-flake nixpkgs channel in the adopt/laptop examples to
nixos-26.05, and add the "Impermanence (optional)" section covering the
/persist subvolume, the required "nixos" fs label, and the default
persistence set.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

2026-08-28 12:38:06 +03:00

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Adopt Nanuqsaurus on an existing NixOS install (no repartitioning)

This repo intentionally does not ship a “one size fits all” nixosConfiguration for installed systems. Disk layouts, filesystems, initrd modules, and bootloader details are machine-specific and live in your local hardware-configuration.nix.

The recommended workflow is to create a small local wrapper flake that:

keeps your machine’s hardware-configuration.nix as the source of truth for mounts/boot,
imports nanuqsaurus as a feature/profile module from its URL,
keeps your personal changes in your own repo (or /etc/nixos).

1) Create a wrapper flake in `/etc/nixos`

On the target machine:

Ensure you have a hardware-configuration.nix (generated by nixos-generate-config).
Create /etc/nixos/flake.nix like this (adjust hostName and stateVersion):

{
  description = "Local wrapper for the nanuqsaurus profile";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-26.05";
    nanuqsaurus = {
      url = "git+https://codeberg.org/randogoth/nanuqsaurus.git";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    nixos-hardware = {
      url = "github:NixOS/nixos-hardware";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = inputs@{ nixpkgs, nanuqsaurus, nixos-hardware, ... }: {
    nixosConfigurations.nanuqsaurus = nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      # Optional: only needed if your local modules require access to flake inputs.
      specialArgs = { inherit inputs; };
      modules = [
        ./hardware-configuration.nix
        # Optional: pick the right hardware module for your machine.
        # Find your model at https://github.com/NixOS/nixos-hardware or use one of these generic profiles:
        #nixos-hardware.nixosModules.common-cpu-intel
        #nixos-hardware.nixosModules.common-cpu-amd
        #nixos-hardware.nixosModules.common-gpu-intel
        #nixos-hardware.nixosModules.common-gpu-amd
        #nixos-hardware.nixosModules.common-gpu-nvidia
        nanuqsaurus.nixosModules.nanuqsaurus
        # Optional: opt into Flox tooling + cache
        # nanuqsaurus.nixosModules.flox
        {
          # Optional: change the default admin username ("admin")
          nanuqsaurus.admin.username = "admin";
          # Optional: enable impermanence (requires a /persist Btrfs subvolume and mounts in hardware-configuration.nix)
          # nanuqsaurus.impermanence.enable = true;
          networking.hostName = "nanuqsaurus";
          system.stateVersion = "25.11";
        }
      ];
    };
  };
}

2) Switch to it

sudo nixos-rebuild switch --flake /etc/nixos#nanuqsaurus

Updating later

If you keep nanuqsaurus.url pointing at the repo, you can update with:
- nix flake update (in /etc/nixos), then
- sudo nixos-rebuild switch --flake /etc/nixos#nanuqsaurus
Keep all your machine-specific changes in the wrapper flake (additional modules, packages, services, etc.).

Impermanence (optional)

If you enable nanuqsaurus.impermanence.enable = true; you must:

Add a /persist mount (Btrfs subvolume) in hardware-configuration.nix.
Migrate state you care about into /persist before the first reboot.

Notes:

The rollback logic expects the root Btrfs volume label to be nixos.
Create the subvolume with btrfs subvolume create /mnt/persist and mount it as /persist.

The default persistence set includes:

/etc/nixos
/etc/ssh
/etc/cups
/var/lib/cups
/var/lib/libvirt
/var/lib/secureboot
/var/lib/tailscale
/var/lib/systemd
/var/lib/nixos
/etc/machine-id

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