global .vimrc?

> I set bg=dark in my ~/.vimrc file and everything is fine. The problem is
> that when I run "su -" and then run "vi" on a file I'm back to dark blue
> text on a black background. I looked for a global .vimrc file but can't
> find one. Any pointers?

Yeah, the global one is not a .vimrc, but vimrc. On my Gentoo box it can be
found in /usr/share/vim/vim62/