Tips when rebooting to PXE or USB
When deploying a new unconfigured server, there are no configured disks from which to boot. Therefore, the system must boot from other media, such as a CD or DVD drive, from a USB port, or from the network using the Preboot Execution Environment (PXE). At times, the installation might reboot the server being deployed during the task sequence to complete initialization of a configuration, such as defining array disks.
When using a reboot computer standard action within the task sequence editor, the action requires a writeable partition, either to reboot into the existing operating system or to copy WinPE to the disk and reboot to WinPE again. If you assign a reboot task to a server and these conditions do not exist, the task sequence fails at that action. Without a valid boot partition, the machine cannot be rebooted in the middle of a task sequence.
If you use PXE and the server simply ends the task sequence and reboots on its own, Configuration Manager does not readvertise the PXE boot to the computer. The PXE advertisement must be reset if it is to run the same task sequence again. Therefore, the server will likely reboot into an unknown state and stop at a No Operating System prompt. You could assign a second task sequence to the server, but when the first task sequence ends, the second starts immediately, without a reboot between them.
If you used boot media such as CD, DVD, or a USB drive, the result is the same; the task fails when the reboot task runs because a valid boot partition does not exist. If you make the task sequence end instead of rebooting, the system reboots and starts the task sequence again. Without some sort of conditional flow control, the installation reruns the same tasks.