> 	You can union mount another file system on top of it (or
> 	mount it under another filesystem) (See mount_union).
> 
> > How can I store the builded objects of a source tree in
> > a diffrent file system

A somewhat safer alternative is to mount a new filesystem under /usr/obj
(or symlink /usr/obj to a place where you have space), and run "make
obj" from /usr/src.  This will put all of the generated files under
/usr/obj.  If your sources are not in /usr/src, then you'll need to
modify /usr/share/mk/bsd.own.mk to match your configuration or set
BSDSRCDIR and BSDOBJDIR in your environment (to override those values).

-allen

-- 
              Allen Briggs - end killing - briggs@macbsd.com