I'm using php5-fpm on ubuntu 12.04, and have separate pools and chroot locations for each domain hosted with nginx. However, I know that some system files need to be directly in the jail, but which ones do I need?

I know that dns resolution isn't working currently, and I have read a few articles that say I need to copy some of the system core files into the directory, but they never really go into details of which ones I actually need to copy into there.

I know there is something for dns, timezone (php seems to error for any time/date related functions).

And I was just wondering about the use of chroot in general. Is it even worth using it or would it be more secure to have a separate partition for each domain, or even just having a separate vm for each domain (which would cost more resources)?