Using Citrix App Layering (UniDesk) with FSLogix RRS feed

  • General discussion

  • Into what Layer should FSLogix be installed when into using Citrix App Layering (UniDesk)?

    • OS Layer = Lowest (FSLogix can be installed here, Include and Exclude Lists have to go here)
    • Platform Layer = Normal (FSLogix is normally installed here)
    • App Layer = Doesn't work well (FSLogix should NOT be installed here)


    How to adjust driver (frxdrvvt) altitude with UniDesk

    With the standard driver altitudes, the UniDesk filter driver (App Layering) can prevent file system calls getting to the FSLogix driver


    When calls for files are made in Windows, they enter the file system I/O stack. Filter drivers register with the filter manager for a chosen set of calls. They also register in a certain order according to the 'altitude' value assigned by Microsoft. Drivers registered at higher numbers see the calls coming down the stack first and if they handle the call, drivers at a lower altitude may never see the request.


    At the currently implemented altitudes, the UniDesk/App Layering driver loads above the FSLogix redirection driver (frxdrvvt). This means calls which frxdrvvt should handle if not excluded from being processed by the UniDesk filter driver never reach the FSLogix driver. To resolve this issue the altitude of the frxdrvvt driver can be adjusted to another value already assigned to FSLogix. Note: we are also investigating making this change permanent.


    The main symptom of this issue are that the VHD is created and formatted but no data is captured into the VHD. To resolve this please make the following change.


    To change the frxdrvvt altitude:

    • Edit HKLM\System\CurrentControlSet\Services\frxdrvvt\Instances\frxdrvvt\Altitude
    • Set the value to 138010 (Note: do not set this to any other value. Spurious results make occur. This value has been assigned to FSLogix by Microsoft)
    • Then reboot

    Monday, June 24, 2019 11:03 PM