If set to false, mkDerivation will throw an exception if a package has
an unfree license. ‘release-lib.nix’ uses this to enforce that we
don't build unfree packages as part of the Nixpkgs channel. Since
this is set through Nixpkgs' ‘config’ argument, it's more finegrained
than $HYDRA_DISALLOW_UNFREE.
modules) together in an attribute set returned by the function
"kernelPackagesFor" that takes a kernel as argument. For instance,
kernelPackages_2_6_23 is the result of calling this function with
kernel_2_6_23.
This is necessary in NixOS to make it easier to override the kernel:
it's not enough to just specify a different kernel (via the
boot.kernel option), but you also need matching nvidiaDriver, aufs,
iwlwifi, etc. Having a single attribute set that contains all
kernel-related packages makes this much easier.
* The kernel now has a passthru attribute "features" that allows NixOS
expressions to test whether a kernel has certain features. For
instance, the externel "iwlwifi" kernel module package should only
be built on kernels < 2.6.24, as kernels >= 2.6.24 have iwlwifi
support integrated. So the NixOS expressions can do the test
"kernel.features ? iwlwifi" to see if the iwlwifi package should be
built.
Kernel patches can declare additional features. E.g., the fbsplash
patch adds a "fbSplash" feature.
svn path=/nixpkgs/trunk/; revision=11881
