nixpkgs/nixos/doc/manual/development/testing-installer.chapter.md

Testing the Installer

Building, burning, and booting from an installation CD is rather tedious, so here is a quick way to see if the installer works properly:

# mount -t tmpfs none /mnt
# nixos-generate-config --root /mnt
$ nix-build '<nixpkgs/nixos>' -A config.system.build.nixos-install
# ./result/bin/nixos-install

To start a login shell in the new NixOS installation in /mnt:

$ nix-build '<nixpkgs/nixos>' -A config.system.build.nixos-enter
# ./result/bin/nixos-enter