“DOS Devices” to directory (aka permanent SUBST) not honored after Windows 21H1 update

Previously, a device mapping had been established using HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerDOS Devices to add an alias from D: to C:Build. This approach discussed in the wikipedia SUBST article and similar.

After updating to Windows 21H1 this registry setting was removed1, and even after re-adding the setting, the “D:” device is not being enumerate in Explorer, powershell, or bash-git (mingw).

After the installation the “DOS Devices” registry section has been updated1 to add a the registry key shown below. However, this does not seem to take effect. How can I restore this ‘permanent subst’ functionality to a directory target?

Name   Value
D:     \??C:Build
  • 1https://www.satsignal.eu/software/Win-10-notes.html notes that the “DOS Devices” are deleted and have to be manually added back (in Windows 10 build 2004). It makes no mention of this functionality being removed. I have re-added the DOS Devices entry back and the mapped drive is still not appearing.

  • Using WinObj (from Winternals) shows the correct Name and Symbolic Link Target in GLOBAL?? for “D:”.

  • The “C:Build” directory exists with standard permissions (eg. SYSTEM full control, Authenticated Users all-but full control, Users with read access).

  • This was an in-place update of Windows 10; pre-20H2.