I want to sell off some of my excess bandwidth from the VPS, but to do that I'll need to monitor how much bandwidth each customer is using. Each customer will have their own vhost file, so obviously their own DocumentRoot, so is there any way to monitor how much traffic that directory is getting?
Lxadmin is a cheap VPS control panel which supports administration, reselling and customer access. You should try it out to monitor bandwidth.
I want to do it all myself; making the control panel myself, I mean. I found cband, which seems to do okay