A rebuild script that commits on a successful build

configuration.nix

{
  config,
  pkgs,
  options,
  ...
}: let
  hostname = "oatman-pc"; # to alllow per-machine config
in {
  networking.hostName = hostname;

  imports = [
    /etc/nixos/hardware-configuration.nix
    (/home/oatman/dotfiles/nixos + "/${hostname}.nix")
  ];
}

nixos-rebuild.sh

#!/usr/bin/env bash
#
# I believe there are a few ways to do this:
#
#    1. My current way, using a minimal /etc/nixos/configuration.nix that just imports my config from my home directory (see it in the gist)
#    2. Symlinking to your own configuration.nix in your home directory (I think I tried and abandoned this and links made relative paths weird)
#    3. My new favourite way: as @clot27 says, you can provide nixos-rebuild with a path to the config, allowing it to be entirely inside your dotfies, with zero bootstrapping of files required.
#       `nixos-rebuild switch -I nixos-config=path/to/configuration.nix`
#    4. If you uses a flake as your primary config, you can specify a path to `configuration.nix` in it and then `nixos-rebuild switch —flake` path/to/directory
# As I hope was clear from the video, I am new to nixos, and there may be other, better, options, in which case I'd love to know them! (I'll update the gist if so)

# A rebuild script that commits on a successful build
set -e

# Edit your config
$EDITOR configuration.nix

# cd to your config dir
pushd ~/dotfiles/nixos/

# Early return if no changes were detected (thanks @singiamtel!)
if git diff --quiet '*.nix'; then
    echo "No changes detected, exiting."
    popd
    exit 0
fi

# Autoformat your nix files
alejandra . &>/dev/null \
  || ( alejandra . ; echo "formatting failed!" && exit 1)

# Shows your changes
git diff -U0 '*.nix'

echo "NixOS Rebuilding..."

# Rebuild, output simplified errors, log trackebacks
sudo nixos-rebuild switch &>nixos-switch.log || (cat nixos-switch.log | grep --color error && exit 1)

# Get current generation metadata
current=$(nixos-rebuild list-generations | grep current)

# Commit all changes witih the generation metadata
git commit -am "$current"

# Back to where you were
popd

# Notify all OK!
notify-send -e "NixOS Rebuilt OK!" --icon=software-update-available

I have a laptop with only two cores and - since everytime I started a rebuild it would freeze my desktop - I implemented the simplest throttling mechanism to tell nixos-rebuild to use only half of the available cores (snippet below)

# Detect processors
procs="$(nproc)"
if [ -z "${procs:-}" ]; then
	echo "No processors detected! Assuming 2..."
	procs="2"
fi

hprocs="$(( procs / 2 ))"
echo "Detected ${procs} processors, using ${hprocs} of them"

nixos-rebuild switch --max-jobs "${hprocs}" #...