Boot images have an option to enable a command shell while running in Windows PE. This is turned off by default for security reasons (since it would allow an end user to open a command shell during the re-imaging process) but can be enabled on the “Windows PE” property page.
Open the boot image’s properties dialog
On the Windows PE tab check the “Enable command support (testing only)” option
Update the boot image on the distribution points
Rebuild any media that uses the boot image (e.g. capture media, boot media, or stand-alone media)
When a task sequence is running in Windows PE you can open a command shell by pressing F8. As long as the command-shell is open the task sequence will not reboot the machine. This will give you a chance to verify network connectivity, diagnose driver issues, and view/copy the log files (see Client Log Files section below).