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There are these similar questions like mine already: How do I mount the EFI partition on Windows 8.1 so that it is readable and writeable?

But, my trouble is that these methods are not working for mounting an EFI partition located on a flash drive on my Windows 10 (Version: 1709, Build: 16299.309) PC.

Following is a screenshot of the message I get in a command prompt using the diskpart utility:

command prompt window running diskpart

What would be a workaround here?

Scott - Слава Україні
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Subho
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2 Answers2

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I found a way for it to work using mountvol by issuing mountvol /? first.

The output will have some hint at the end and in my case it was:

Possible values for VolumeName along with current mount points are:

\\?\Volume{38d5d60e-5760-43bc-85ac-25f3452b2e2f}\
    *** NO MOUNT POINTS ***

\\?\Volume{5f7cfdd0-dc43-0c6f-e24a-85ed1e43d782}\
    E:\

\\?\Volume{b08ddf00-9937-413c-82e9-c0e55525e46f}\
    *** NO MOUNT POINTS ***

\\?\Volume{07434f9f-e9d4-11e9-84c3-7085c2c582c4}\
    *** NO MOUNT POINTS ***

\\?\Volume{07434fa0-e9d4-11e9-84c3-7085c2c582c4}\
    D:\

\\?\Volume{45ce4d69-be26-4a9e-bc11-d850c69875ec}\
    C:\

After some tries (you can test one by one), the command that worked for me is:

mountvol h: \\?\Volume{07434f9f-e9d4-11e9-84c3-7085c2c582c4}\

Then find a way to access H:, which shows up: open Task Manager > File > Run New Task, and browse to it.

JW0914
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Lan Nguyen
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    It works, thx! You can find the correct Volume ID with WinObj.exe (from Sysinternals). Click on GLOBALS?? on the left and sort by SymLinks in the right window. In the column Names you find something like Harddisk0Partition2 and just above the corresponding Volume ID. – seizu Sep 04 '20 at 15:50
  • I did just like seizu did but instead copy the GUID from mountvol then paste to search, it will show up the harddisk and partition, then choose the one you need. – raspiduino Feb 06 '22 at 03:10
  • This works but doesn't allow you to copy or delete any of the data on the partition. – Squashman Dec 27 '22 at 02:14
  • Ok. I figured it out. You need to access the mounted volume from a program with elevated privileges. So you can either just go directly to X: from the cmd prompt and use robocopy or launch any other Windows Explorer type program as admin. – Squashman Dec 27 '22 at 05:37
2

You can do it easily using Windows PowerShell without using any third-party apps.

Lets assume disk number is 4 and EFI partition number is 1.

  1. Open PowerShell with Admin privileges.

  2. Use the following syntax with a respectable drive letter and a partition number.

    Add-PartitionAccessPath -DiskNumber 4 -PartitionNumber 1 -AccessPath "Z:"

This will mount the EFI volume "Z". (you can't access the volume using windows explorer without Admin privileges , So use third-party apps like 7Zip File manager(run as Administrator) etc..)

Lalith J.
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