[Nix-dev] how to install nilfs-utils ?

[Michael Raskin]

>I am trying to install nilfs-utils.
>
>According to the wiki ( http://nixos.org/wiki/Install/remove_software ), I can
>install a package by 'nix-env -i <package> for one user, or I can install it
>for all users by adding it to environment.systemPackages . The second way does
>not work for me for nilfs-utils. If I put
>
>  environment.systemPackages = with pkgs; [
>     wget httpfs2
>     nilfs-utils
>  ];
>
>in /etc/nixos/configuration.nix, then nix complains:
>
>$ nixos-rebuild build
>building Nix...
>building the system configuration...
>error: undefined variable `nilfs-utils'
>
>but other packages like wget or httpfs2 are fine.
>Also 'nix-env -i nilfs-utils' works fine.
>
>What is wrong with putting nilfs-utils in environment.systemPackages ?
>Does it have something to do with the hyphen in the name, or is nilfs-utils a
>special kind of package ? In the latter case, how can one tell ?
>How can it be installed for all users ?

«nix-env -i» deals with evluated package names
«nix-env -iA» and «systemPackages» deal with attribute names (most are
specified in all-packages.nix).

The difference is more or less the difference between a variable name 
and its value.

nilfs-utils is an old package (added before Nix allowed dashes inside 
variable names) and it haven't been updated for a while. So it is listed
in all-packages.nix using attribute name nifs_utils.

The simplest way to find out is currently looking at al-packages.nix
in pkgs/top-level directory at nixpkgs repository.