[Nix-dev] multiarch?

[Isaac Dupree]

Debian is working on a "multiarch" setup that allows packages for 
multiple architectures (e.g. i686-linux as well as x86_64-linux and even 
powerpc-linux) to be installed in the same system.  It seems that the 
Nix filesystem layout mostly supports this rather easily, even providing 
sharing between packages that were built under different architectures 
but actually had no differences there.  But do the tools? -- can we 
compile under a different architecture than the one we're "primarily" 
running on (I forget whether that's meaningful), and run that x86 
firefox binary?  Can we choose different ones in the boot process, and 
(where possible) switch between them at runtime?  Certainly the same 
partition might be booted from different computers at different times... 
  There is the enticing suggestion (I have no idea how practical) that 
with QEMU and perhaps some help from the kernel to streamline the 
process of running different executables, I could even have my x86(64) 
system provide powerpc-linux as a first-class dependency!

I suppose that one could provide a build hook to say, if needed, "build 
on one of the different architectures this computer can provide". But 
I'm not sure how much infrastructure, or even how much theory, is 
missing in order to actually make good use of such a system?

-Isaac