nix/nixos/common/services/snapper.nix

{ lib, pkgs, desktop, ... }: {
    environment.systemPackages = [ ]  ++ lib.optional (builtins.isString desktop) pkgs.snapper-gui;

    services.snapper = {
        snapshotRootOnBoot = true;
        cleanupInterval = "1d";
        snapshotInterval = "1h";
    };
}