[Nix-dev] Ad hoc vs. declarative package management

[Amy de Buitléir]

I'm curious to understand why this works just fine (as a user)...

    nix-env -i xev
    nix-env -i konsole

...but if I put those packages in /etc/nixos/configuration.nix...

  environment.systemPackages = with pkgs; [
    cabal2nix
    dmenu2
    dzen2
    gnumake
    haskellngPackages.xmonad
    haskellngPackages.xmonad-contrib
    haskellngPackages.xmonad-extras
    haskellngPackages.ghc
    haskellngPackages.cabal-install
    konsole # causes an error
    gitAndTools.gitFull
    meld
    unison
    unzip
    wget
    xev # causes an error
    xsel
  ];

... I get errors (see below). Is this a bug, or are there some limitations
on which packages I can install declaratively?

[amy at wombat9000:~/Downloads]$ sudo nixos-rebuild switch
building Nix...
building the system configuration...
error: undefined variable ‘konsole’ at "/etc/nixos/configuration.nix":47:5
(use ‘--show-trace’ to show detailed location information)


[amy at wombat9000:~/Downloads]$ sudo nixos-rebuild switch
building Nix...
building the system configuration...
error: undefined variable ‘xev’ at "/etc/nixos/configuration.nix":53:5
(use ‘--show-trace’ to show detailed location information)