From NixOS Wiki

I fixed the syntax in the section on "How can I manage software with nix-env like with configuration.nix?" but it still doesn't work for me and there are lines of code there that are not explained (so probably should be bu I don't understand).


     inherit ((import <nixpkgs/nixos> {}).config.system.path)
     pathsToLink ignoreCollisions postBuild;
     extraOutputsToInstall = [ "man" ];


What does all that mean? And is it compulsory? If I leave it in I get this:

``` $ nix-env -iA userPackages -f '<nixpkgs>' installing 'user-packages' error: file 'nixos-config' was not found in the Nix search path (add it using $NIX_PATH or -I), at /home/dsyer/.nix-defexpr/channels/nixpkgs/nixos/default.nix:1:60 (use '--show-trace' to show detailed location information ```

If I remove it I get:

``` $ nix-env -iA userPackages -f '<nixpkgs>' installing 'user-packages' building '/nix/store/59z3yxcxnm2cs2922gwnjk882v5n9rk9-user-environment.drv'... error: packages '/nix/store/fjm4sqv4ms737c7jsv36l3y8b320vqfg-git-2.25.1/share/man/man7/gittutorial-2.7.gz' and '/nix/store/5yxbj5d6w10rrxi9r33954qayxyipykf-git-2.25.1/share/man/man7/gittutorial-2.7.gz' have the same priority 5; use 'nix-env --set-flag priority NUMBER INSTALLED_PKGNAME' to change the priority of one of the conflicting packages (0 being the highest priority) builder for '/nix/store/59z3yxcxnm2cs2922gwnjk882v5n9rk9-user-environment.drv' failed with exit code 1 error: build of '/nix/store/59z3yxcxnm2cs2922gwnjk882v5n9rk9-user-environment.drv' failed ```