Duplicatin a sub-site

Hi,

I want to duplicate a sub-domain subsite like sub.domain.com and create a second sub-domain sub-site llike sub2.domain.com. I want to the second copy sub-site to be completely identical including the theme, css file, plugins, their properties, existing posts and pages and stuff.

What is the best way to do this? Is there a plugin to be recommended?

Thanks,

Akasya