Network boot with changes written to local disk

I'd like a few different virtual machines to boot from a single shared base distribution, but write changes to their local disks. I'm wondering if anyone has attempted this and what technology they've used. NFS? iSCSI? OverlayFS?

Any pointers/guides/howtos that you've come across would be appreciated as I've only done a very simple PXE boot before where I had single PXE client and single server.

thanks,
Biff.