[Nix-dev] disk setup for nixos installation

[Michael Raskin]

>On further reflection, I think I see how it almost might work using
>derivations.  Assume it is possible to have a derivation that is only
>considered to be built (hand-waving part here ...) if the required filesystem
>exists. Then that derivation depends on another that is only considered to be
>built if the necessary LVM volume exists, etc. . I still cannot see how to
>make the hand-waving part referentially transparent.
>
>I think nixos must have a solution to this problem, otherwise how can it
>install GRUB ?

NixOS way is to generate the needed scripts (preferably, the scripts 
can be safely run the second time after success) and run them.