which NixOS should be built. This is useful in NixOS network
specifications, because it allows machines in the network to have
different types, e.g.,
{
machine1 =
{ config, pkgs, ... }:
{ nixpkgs.system = "i686-linux";
... other config ...
};
machine2 =
{ config, pkgs, ... }:
{ nixpkgs.system = "x86_64-linux";
... other config ...
};
}
It can also be useful in distributed NixOS tests.
svn path=/nixos/trunk/; revision=24823
be set from the NixOS configuration. For instance, you can say
nixpkgs.config.firefox.enableGeckoMediaPlayer = true;
environment.systemPackages = [ pkgs.firefox ];
but the more interesting application is to apply global overrides to
Nixpkgs throughout NixOS, e.g.
nixpkgs.config.packageOverrides = pkgs:
{ glibc = pkgs.glibc27;
gcc = pkgs.gcc42;
};
would build the whole system with Glibc 2.7 and GCC 4.2. (There are
some issues with "useFromStdenv" in all-packages.nix that need to be
fixed for packages in the stdenv bootstrap though.)
The implementation of this option is kind of evil though due to the
need to prevent a circularity between the evaluation of
nixpkgs.config and the "pkgs" module argument.
svn path=/nixos/trunk/; revision=16866
