Write Filter & ThinMan Profile
Keep in mind that all configurations related to the Write Filter can be automatically distributed across multiple devices using ThinMan Profiles and Policies. For more details, refer to Use ThinMan Profile and Policy to send configuration automatically.
¶ What is the Purpose of the Write Filter?
The write filter is used to protect a device's disk or flash memory from unwanted writes and to minimize unnecessary activity on the flash memory. By redirecting I/O requests from running processes to temporary storage in RAM, the write filter keeps data accessible to users while the thin client is powered on. However, no permanent changes are saved to the flash memory during operation, allowing the device to return to its previous configuratio upon reboot.
This feature helps to extend the lifespan of flash memory and is especially useful in environments where memory stability and longevity are essential.
Windows Embedded uses a write filter which has to be disabled in order to allow permanently writing onto the disk. Remember that changing the write filter status needs a device reboot.
Microsoft Windows Unified Write Filter
For more information, read Microsoft Windows Unified Write Filter feature
Software Installation
Be sure to disable the write filter before installing new software on the thin client. Then, reboot the thin client to be sure the writing starts on a "clean" installation. Only the changes made after the reboot are saved on the DoM. Finally, enable the write filter (this will reboot the thin client) to protect the DoM from undesired writings.
Mutiple Software Installation
If you plan to install multiple software, disable the write filter. In this way any change is saved to the flash memory. Remember to enable the write filter once you have installed all the software.
Software Installation from ThinMan
When installing software from ThinMan on write filter protected devices; ThinMan will automatically enable/disable the write filter. For more information, read How to manually install third-party software on Windows Devices from ThinMan. You could also create a Scheduled Activities or an Event Activity from ThinMan.
¶ Write Filter configuration panel
The Write Filter is enabled by default on Praim Windows Embedded devices.
If you install Agile on a PC with Windows Enterprise or Windows Education license you will need to activate the Microsoft Write Filter in order to use the Write Filter feature.
Below it is shown the Write Filter configuration panel of the Agile Configurator.
You can Enable or disable the Write Filter by checking or un-checking the checkbox.
On the right side, you will find the information related to the write filter. To modify the write filter configuration click on Configure, it will open the window below.
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Drive: Volume where you want to activate the Write Filter protection.
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Maximum size: maximum amount of RAM allocated to the write filter.
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Warning threshold: threshold beyond which the system warns that the amount of memory allocated to the write-filter is running out.
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Critical threshold: threshold beyond which the system warns that the amount of memory allocated to the write-filter is exhausted.
Do not modify these parameters unless it is necessary
If you decide to modify the maximum size parameter, do it based on the thin client's RAM and depending on how much space you want to give the write filter's overlay. After modifying the parameters it is highly recommended to close the applications or restart the system.
¶ Excluded Files
Once the Unified Write Filter is active, it can be configured to exclude specific directories or files from the protection. In this case, the changes made to directories and files are saved directly to the hard disk. You can Add Directory or Add File to the exclusion list by clicking on the corresponding button. A file explorer is opened, select the file or the directory to exclude from the write filter and click on the button to confirm. Files and directories are added to the list. Reboot the device to accept the changes.
UWF Exclusion List - 4 Steps
To use the exclusion list follow these steps:
Disable the write filter and reboot the device
Create the files and the directories that you want to exclude from the write filter
Enable the write filter and reboot the device
Add the created files and directories to the exclusion list.
Some files and directories are always excluded, see below Exceptions for Praim Windows Embedded Devices.
Rebooting
If you change the status of the write filter or add directories or files to the exclusion list, you must restart the device for the changes to take effect. Agile will remind you that the modifications you made require a reboot of the device. You can proceed with the restart by clicking on the Reboot button.
¶ Exceptions for Praim Windows Embedded devices
To be sure that the system works under various circumstances some directory and some registry keys remain writable from the operating system even if the write filter is enabled. Above you find the list of File System Exceptions and Registry Exceptions defined by default in the Praim devices. In case of installation of Agile on other devices be sure that the write filter is correctly configured.
File System Exceptions
- %SystemDrive%\Program Files\Windows Defender
- %SystemDrive%\Windows\WindowsUpdate.log
- %SystemDrive%\Windows\Temp\MpCmdRun.log
- %SystemDrive%\ProgramData\Microsoft\Windows Defender
- %SystemDrive%\ProgramData\Praim\Logs
- %SystemDrive%\ProgramData\Praim\Profile
Registry Exceptions
- HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender
- HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones
- HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation
- HKEY_LOCAL_MACHINE\SOFTWARE\Praim