building with package directory over NFS

[Mayuresh <mayuresh%acm.org@localhost>]

My setup involves nfs mounted packages directory on a Linux qemu guest.
The mount looks like:

10.0.2.2:/usr/local/ubuntu/packages on /packages type nfs (<snip>

On the qemu host 10.0.2.2 the directory is owned by non-root user who
launches qemu. Would prefer to not launch qemu as root as far possible. In
/etc/exports -maproot maps remote root to the same non-root user.

Now, on the Linux guest, I build package as root, write access to packages
directory works, though I get the following error.

=> Creating binary package /packages/All/boost-jam-1.73.0.tgz
/bin/cp: failed to preserve ownership for
'/packages/All/boost-jam-1.73.0.tgz': Operation not permitted
*** Error code 1

What is needed for this to work? Unprivileged build with uid on host and
guest being same might be an option. But it's less flexible. Anything
better possible?

Mayuresh