copy a whole partition excluding specified.

Scenario:

I would want to copy my / to /mnt, and to avoid recursion exclude /mnt.

cp -avx / /mnt

If i use the above i believe it would run recursively, and end up in mess. So how to do it ?!
Basically this / is sda1, and /mnt is sda2 and sda1 is where only OS is available & currently booted.

Ultimately, my question is how to backup a path, by excluding a specific directory.

I cannot boot in Live CD and copy. Anybody have experience in doing this, and have some efficient way to do this ?

As man cp states, "x" means "stay on this file system" - meaning in turn that the command given ought to suffice.

Yep, cp -avx did the trick.

It is a simple confusion, thanks anyway.