Dear members
about: mounting FFU file when running WinPE.
You might face error when you try to mount an FFU file on WinPE system.
When mounting FFU file the DISM process
- creates a VHD-file with random file-name in %TEMP% folder.
- applies the FFU-disk-image against the VHD-file.
- attaches the VHD file as virtual disk (w/o letter).
As you can guess, this VHD-file can grow up to several GB size.
By default, the %TEMP% folder on WinPE is on Drive [X:].
You might use ImDisk tool to have a RAM-drive where the %TEMP% folder is created.
In both cases disk-space is limited to some GB.
DISM returns Error when available disk space is used up.
Setting the DISM scratchspace parameter to available hard disk drive is not recognized by DISM.
Solution 1:
Presuming you have a RAM drive (NTFS) with %TEMP% folder and
an existing folder D:\Temp on hard disk drive with enough disk space.
Run MKLINK /D /J %TEMP% [D:\Temp]
It will create a symbolic link %TEMP% which redirects write access to the hard disk.
Now you are ready to mount FFU file to an empty filesystem folder (Mountpoint).
Example (using DISM v.10.0.17763.1):
A fresh installed win11 captured to FFU (6GB file size) mounted to disk in 192 sec. (VirtualBox + SSD)
Consuming 10GB disk space for the VHD file.
Note: The VHD file is deleted as soon as you unmount the FFU image.
When the image is mounted you can access the Mountpoint directly or apply a letter to the attached VHD-disk in disk management.
Now you can update files / delete / copy and paste as you like.
Of course the limit is disk space of [D:] (in our case).
As well you can apply DISM servicing commands against the mountpoint. (see Microsoft documents for details)
As said before:
If you capture a Windows system [C:], FFU files can be twice as large as WIM files, but it takes only a quarter of the time to create them.
Both ways of imaging offer about the same options to service the image.
Best regards T.