# Pastebin wlhYQEM9
darwin-rebuild switch
building the system configuration...
Password:
/nix/store/v7mf8wbmlqd3vkbbky9c3crpzr0225j2-darwin-system-19.09pre178484.8bc70c937b3+darwin4.0000000/activate-user: line 92: nix-instantiate: command not found
error: Changed <darwin-config> but target does not exist, aborting activation
Create ~/.nixpkgs/darwin-configuration.nix or set environment.darwinConfig:

    environment.darwinConfig = "***";

And rebuild using (only required once)
$ darwin-rebuild switch -I "darwin-config=***"