Write Filter Support

Windows Embedded Standard includes a Write Filter feature that enables writes to disk to be redirected to RAM or a temporary volume. The image on the device is then consistently persisted and every session on that device, following a restart, is the same. Device Manager 2011 supports the following types of write filters:

If you receive a device from the device manufacturer with write filters disabled, use the FBWF Manager or EWF Manager command line tools to enable the write filters for the first time. For more information about FBWF Manager, see on MSDN. For more information about EWF Manager, see EWF Manager on MSDN. For more information about how to use a command-line tool with Configuration Manager, see Run Command Line in Configuration Manager Help.

You can use Device Manager 2011 to efficiently update software on managed client devices that have write filters enabled. The following list shows the three ways you can disable and then restore write filters in Device Manager 2011 during a software deployment:

Using custom scripts in packages to disable and restore write filters is optional. If you decide to use custom scripts, use Visual Basic Script and the EDM_WriteFilterAdvertisementFormatter WMI class. Modify the created task sequence to disable write filters, install the software package for the input package/program combination, and then restore write filters. You can also add code to create an advertisement from this task sequence.

During the software update process, Device Manager 2011 uses the following basic procedure. After Device Manager 2011 detects write filters, it saves configuration information. If Hibernate Once Resume Many (HORM) is used on the device, it is deactivated. The device displays a five-minute countdown to warn users that the device is going to be updated, and then disables write filters. Device Manager 2011 restarts the device from the operating system. The device is now locked and only users who have Administrator credentials can log on to the device.

Next, the software deployment starts. Depending on how you have scheduled the software deployment, there may be pauses during the process. When the software update is completed, Device Manager 2011 restores the write filters. If HORM was previously used on the device, Device Manager 2011 restores HORM. Device Manager 2011 restarts the device operating system. If HORM was not used in the past, the process is completed. If HORM has been restored, the device starts hibernation and will restart from the hibernation file when it is needed.

Adding Write Filter Support to Advertisements

Information about how to add write filter support to an advertisement using the New Advertisement with Write Filter Handling Wizard.

Deleting an Advertisement with Write Filter Support

Information about how to delete an advertisement with write filter support.

Adding Write Filter Support to Custom Task Sequences

Information about how to add write filter support to a custom task sequence.