We should probably be trying to emulate a particular version of the
   operating system, in which case we'd have a version number to report,
   even if not the one a particular app would like to see.
   
   It's unlikely that an application other than an LKM is going to do
   what you describe above - on Linux, at least, you pretty much have to
   test for features because there are so many random releases out there.
   If you try to match on a particular version number, you are pretty
   much guaranteed to lose.


"in my world, where linux doesn't exist" ... we have this exact problem
with vendor software, that will *only* run on a particular release of
the host OS.


i'm now not sure if i like the "setuname" vs. the "sysctl for each
emulation" ideas.  perhaps both can be used ....