How can I detect the drive letter of a booted USB drive from script?

Question

I'm launching WinPE 2 from a bootable UFD, and I need to detect the drive letter in order to tell ImageX where to find the WIM. However, depending on the machine I'm imaging, there are different mounted drives.

I need a way to consistently mount the UFD at, say, P: or something. Is there a way to detect the letter of the drive from which the machine was booted, or another way to pass the location of my WIM file to a variable accessible from startnet.cmd?

Here's someone else with the same issue over at TechNet.

http://social.technet.microsoft.com/Forums/en-US/itprovistadeployment/thread/3e8bb8db-a1c6-40be-b4b0-58093f4833be?prof=required#

Solution 1

This VBScript will show a message for each removable drive (letter:description), could be easily modified to search for a particular drive and return the letter.

 
strComputer = "."
Set objWMIService = GetObject("winmgmts:\\" & strComputer & "\root\cimv2")

Set colDisks = objWMIService.ExecQuery("Select * from Win32_LogicalDisk where MediaType = 11")

For Each objDisk in colDisks
    Wscript.Echo objDisk.DeviceID & objDisk.Description
Next

Don't know if that helps at all.

Solution 2

It's a less generic solution than the others mentioned here, but there appears to be a specific way to determine which underlying volume a "RAM-drive-booted" Windows PE OS was booted from. From the documentation on Windows PE in the Windows Automated Installation Kit:

If you are not booting Windows Deployment Services, the best way to determine where Windows PE booted from is to first check for PEBootRamdiskSourceDrive registry key. If it is not present, scan the drives of the correct PEBootType and look for some kind of tag file that identifies the boot drive.

(The registry value in question sits under HKLM\SYSTEM\CurrentControlSet\Control.)