We run a build system using PXE and Puppet which lets us reliably and quickly set up production and development environments on our servers and maintain their consistency.
Every now and again we need to wipe the MBR of a Linux box in order to reboot it so it can PXE boot and reinstall itself. I like to use this command:
dd if=/dev/zero of=/dev/sda bs=446 count=1
which fills up the start of the disk with 0s, a simple reboot will then kick the box and start the PXE cycle!