[root@nixos:~]# nixos-install --show-trace
building the system configuration...
error: while evaluating the attribute ‘buildCommand’ of the derivation ‘nixos-system-slvt-17.09pre104410.65593e6’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/nixos/modules/system/activation/top-level.nix:105:7:
while evaluating ‘optionalString’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/strings.nix:138:26, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/nixos/modules/system/activation/top-level.nix:39:9:
while evaluating the attribute ‘system.modulesTree’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/attrsets.nix:199:44:
while evaluating anonymous function at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:73:45, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/attrsets.nix:199:52:
while evaluating the attribute ‘value’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:310:9:
while evaluating the option `system.modulesTree':
while evaluating the attribute ‘isDefined’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:342:5:
while evaluating ‘filterOverrides’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:417:21, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:326:18:
while evaluating ‘concatMap’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/lists.nix:96:18, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:423:8:
while evaluating ‘concatMap’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/lists.nix:96:18, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:321:17:
while evaluating anonymous function at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:321:28, called from undefined position:
while evaluating ‘dischargeProperties’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:384:25, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:322:62:
while evaluating ‘dischargeProperties’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:384:25, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:390:11:
while evaluating the attribute ‘content’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:465:14:
while evaluating the attribute ‘modulesTree’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/nixos/modules/system/boot/kernel.nix:165:5:
while evaluating the attribute ‘boot.extraModulePackages’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/attrsets.nix:199:44:
while evaluating anonymous function at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:73:45, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/attrsets.nix:199:52:
while evaluating the attribute ‘value’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:310:9:
while evaluating the option `boot.extraModulePackages':
while evaluating the attribute ‘mergedValue’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:337:5:
while evaluating anonymous function at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:337:32, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:337:19:
while evaluating ‘merge’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/types.nix:179:20, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:340:8:
while evaluating anonymous function at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/types.nix:180:35, called from undefined position:
while evaluating anonymous function at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/lists.nix:88:28, called from undefined position:
while evaluating anonymous function at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/types.nix:182:22, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/lists.nix:88:31:
while evaluating the attribute ‘optionalValue’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:344:5:
while evaluating ‘filterOverrides’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:417:21, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:326:18:
while evaluating ‘concatMap’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/lists.nix:96:18, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:423:8:
while evaluating ‘concatMap’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/lists.nix:96:18, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:321:17:
while evaluating anonymous function at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:321:28, called from undefined position:
while evaluating ‘dischargeProperties’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:384:25, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/modules.nix:322:62:
while evaluating the attribute ‘value’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/types.nix:186:40:
while evaluating the attribute ‘boot.kernelPackages.broadcom_sta’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/pkgs/top-level/all-packages.nix:11683:5:
while evaluating ‘callPackageWith’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/customisation.nix:95:35, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/pkgs/top-level/all-packages.nix:11683:20:
while evaluating ‘makeOverridable’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/customisation.nix:54:24, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/customisation.nix:99:8:
while evaluating anonymous function at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/pkgs/os-specific/linux/broadcom-sta/default.nix:1:1, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/lib/customisation.nix:56:12:
while evaluating ‘mkDerivation’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/pkgs/stdenv/generic/default.nix:111:5, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/pkgs/os-specific/linux/broadcom-sta/default.nix:14:1:
while evaluating ‘throwEvalHelp’ at /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/pkgs/stdenv/generic/default.nix:199:23, called from /tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/pkgs/stdenv/generic/default.nix:240:21:
Package ‘broadcom-sta-6.30.223.271-4.9.17’ in ‘/tmp/root/nix/store/b8jxvw7a7p7clljzj53bf2jm1vksv98m-nixos-17.09pre104410.65593e6/nixos/pkgs/os-specific/linux/broadcom-sta/default.nix:54’ has an unfree license (‘unfreeRedistributable’), refusing to evaluate.

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnfree = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnfree = true; }
to ~/.config/nixpkgs/config.nix.