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You can't access an EFI system partition with the Mountvol utility in a WinPE Environment

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This article provides a solution to an issue that you can't gain access to the Extensible Firmware Interface (EFI) system partition by using the mountvol /s command when you use the Mountvol utility (Mountvol.exe) in a WinPE Environment.

Applies to:   Windows 10 - all editions, Windows Server 2012 R2
Original KB number:   315943

Symptoms

If you use the Mountvol utility (Mountvol.exe) in a Windows Preinstall Environment (WinPE) on either a Windows XP-based or Windows Server 2003-based computer, you can't gain access to the Extensible Firmware Interface (EFI) system partition by using the mountvol /s command. For example, if you try to use the mountvol x: /s command, you may receive the following error message:

The system cannot find the file specified.

Cause

This behavior occurs because the Mountvol utility isn't supported in WinPE environments.

Resolution

To work around this behavior, use the Diskpart utility (Dispart.exe) instead of the Mountvol tool. To use the Diskpart utility:

  1. Select Start, select Run, type diskpart in the Open box, and then select OK.
  2. When the Diskpart utility starts, type select disk n at the prompt (where n is number for the mapped ESP disk), and then press ENTER.
  3. Type select partition
    n at the prompt (where n is number for the mapped ESP partition), and then press ENTER.
  4. Type assign letter= x at the prompt (where x is the drive letter that you want to assign), and then press ENTER.

After you follow these steps, you can access an EFI system partition by using the drive letter that you assign to the partition with the Diskpart utility.

Status

This behavior is by design.

Data collection

If you need assistance from Microsoft support, we recommend you collect the information by following the steps mentioned in Gather information by using TSS for deployment-related issues.