Common Write Filter Exclusions (Standard 8)
12/1/2014
Review sample code and information for common Write Filter exclusions in Windows Embedded 8 Standard (Standard 8).
Some services and features write information to a device’s persistent volume, and expect that information to be present across device restarts. These services and features generally are not aware of the existence of write filters on a system, so you may need to configure your write filter to allow for specific file and registry exclusions in order for these services and features to work correctly.
This topic lists registry and file exclusions that can help enable some common services and features to work correctly when write filters are enabled.
Customer Experience Improvement Program (CEIP)
When you choose to participate in the CEIP, your computer or device automatically sends information to Microsoft about how you use certain products. Information from your computer or device is combined with other CEIP data to help Microsoft solve problems and to improve the products and features customers use most often.
CEIP data is stored in files that have a .sqm file name extension. To make sure that the CEIP data in the .sqm files is available on a device that has write filters enabled, you can add file and folder exclusions for the .sqm files and folders.
To locate the .sqm files and folders on your device, search for .sqm files by using File Explorer. Alternately, at a command prompt with administrator rights at the root of the drive, type the following command to obtain a list of .sqm files on the device:
dir *.sqm /s
Add file and folder exclusions as required for any .sqm files located on your device.
Add registry exclusions for the following registry keys:
- HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\SQMClient\Windows\CEIPEnable
- HKEY_LOCAL_MACHINE\Software\Microsoft\SQMClient\Windows\CEIPEnable
- HKEY_LOCAL_MACHINE\Software\Microsoft\SQMClient\UploadDisableFlag
Background Intelligent Transfer Service (BITS)
Background Intelligent Transfer Service (BITS) downloads or uploads files between a client and server and provides progress information related to the transfers.
Add file exclusions for the following folders and files:
- % ALLUSERSPROFILE%\Microsoft\Network\Downloader
Add registry exclusions for the following registry keys:
- HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\BITS\StateIndex
Windows Explorer
When write filters are active and you attempt to delete an excluded file or folder in Windows Explorer, the system attempts to move the file or folder to the Recycle Bin. This causes an error, because you cannot move files that are not filtered to a location that is write filter protected.
To work around this, you can disable the Recycle Bin. Alternatively, the user can press Ctrl+Shift and then left-click on the file to directly delete the excluded file, bypassing the Recycle Bin, or the user can delete the excluded file directly from command line.
Networks
When you use write filters on your device, you can add file and registry exclusions to enable your device to join wired and wireless networks. The following file and registry exclusions may be required on your device.
Client Group Policy Object (GPO) registry keys:
- Wireless: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Wireless\GPTWirelessPolicy
- Wired: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WiredL2\GP_Policy
GPO policy files:
- Wireless: C:\Windows\wlansvc\Policies
- Wired: C:\Windows\dot2svc\Policies
Interface profile registry keys:
- Wireless: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\wlansvc
- Wired: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\dot3svc
Interface policy file:
- Wireless: C:\ProgramData\Microsoft\wlansvc\Profiles\Interfaces\{<Interface GUID>}\{<Profile GUID>}.xml
- Wired: C:\ProgramData\Microsoft\dot3svc\Profiles\Interfaces\{<Interface GUID>}\{<Profile GUID>}.xml
Services registry keys:
- Wireless: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Wlansvc
- Wireless: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\WwanSvc
- Wired: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\dot3svc
Daylight Savings Time (DST)
When you use write filters on your device, you can add registry exclusions to persist daylight savings time (DST) settings on your device.
If you are using Unified Write Filter (UWF) on your device, add the following registry exclusions:
- HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones
- HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation
If you are using Enhanced Write Filter (EWF) or File-Based Write Filter (FBWF) on your device, add the following registry exclusion:
- HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal
For more information about daylight savings time (DST) settings on your device, see Write Filters and Automatic Adjustment of Daylight Saving Time.