Sane stable stateless NixOS setup

This is a fairly straightforward setup for making a NixOS system configuration stateless without relying on experimental Nix features.

This means:

• nix-channel is disabled
• Nixpkgs is managed with niv [^1]
• The same Nixpkgs is used for the system and all Nix commands
• This includes the Nixpkgs version, config and overlays

[^1]: Yes niv is a third-party tool, but it's essentially just a nice wrapper around nix-prefetch-url and co.

Usage

We're assuming that you just installed NixOS by going through the official installation docs.

Setup

1. Clone this repo to a local directory and enter it:

   nix-shell -p git --run \
    'git clone https://github.com/infinisil/sane-stable-nixos nixos'
   cd nixos

2. Add your initial NixOS configuration files, either
   • Move your existing configuration files into it:

     sudo mv /etc/nixos/* .

   • Generate new ones:

     nixos-generate-config --dir .

3. Pin Nixpkgs to the latest stable version using niv:

   nix-shell -p niv --run \
    'niv init --nixpkgs NixOS/nixpkgs --nixpkgs-branch nixos-23.11'

4. Remove all stateful channels:

   sudo rm -v /nix/var/nix/profiles/per-user/*/channels*

5. Rebuild:

   sudo ./rebuild switch

6. Log out and back in again.

Making changes

Here are some changes you can make:

• Change the NixOS configuration in ./configuration.nix
• Update the pinned Nixpkgs:

  niv update nixpkgs

• Upgrade to a newer release:

  niv update nixpkgs --branch nixos-23.11

• Change the Nixpkgs config by editing nixpkgs/config.nix
• Add Nixpkgs overlays to nixpkgs/overlays.nix
• Regenerate the hardware configuration:

  nixos-generate-configuration --dir .

To apply the changes, run

sudo ./rebuild switch

All options to ./rebuild are forwarded to nixos-rebuild.

After rebuilding, the changes are reflected in the system. Furthermore, all Nix commands on the system will also use the the same values.