Compaq 6720t HP 6720t Mobile Thin Client Administrator Reference Guide - Windo - Page 19

Enhanced Write Filter (EWF), Using the Enhanced Write Filter (EWF) command line control utility

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2 Enhanced Write Filter (EWF) The Enhanced Write Filter (EWF) provides a secure environment for your computer by protecting it from undesired flash memory writes (the operating system and functional software components reside in flash memory). The write filter also extends the life of the computer by preventing excessive flash write activity. Instead of allowing writes directly to the flash memory, it intercepts all flash writes and caches them. In order to save changes to system configuration settings, you must disable the write filter cache or perform the -commit command during the current boot session. Otherwise, the new settings will be lost when the computer is shut down or restarted. If you do not want to make permanent changes, you can enable the write filter. The write filter cache contents are not lost when you log off and on again (as the same or different user). You can disable the write filter cache after the new logon and still retain the changes. After you disable the write filter, all future writes during the current boot session are written to the flash with no further caching until the computer is restarted. You can also enable/disable the write filter using the command line. NOTE: Always enable the write filter after you have made all of your permanent changes. NOTE: Only an account with administrator privileges can enable, disable, or commit the enhanced write filter. Using the Enhanced Write Filter (EWF) command line control utility CAUTION: Terminal Administrators should use Microsoft® Windows NT® file security to prevent undesired usage of these commands. CAUTION: When using the -commit command, all of the temporary contents are permanently written to the flash memory. NOTE: Because the Enhanced Write Filter commands are executed on the next boot, you must restart the computer for the command to take effect. Windows® Embedded includes the EWF command line control utility. This utility enables you to issue a set of commands to the EWF driver, report the status of each protected volume overlay, and report the format of the overall EWF configurations. Using the Enhanced Write Filter (EWF) command line control utility 9

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2
Enhanced Write Filter (EWF)
The Enhanced Write Filter (EWF) provides a secure environment for your computer by protecting it from
undesired flash memory writes (the operating system and functional software components reside in
flash memory). The write filter also extends the life of the computer by preventing excessive flash write
activity. Instead of allowing writes directly to the flash memory, it intercepts all flash writes and caches
them.
In order to save changes to system configuration settings, you must disable the write filter cache or
perform the
-commit
command during the current boot session. Otherwise, the new settings will be lost when the computer
is shut down or restarted. If you do not want to make permanent changes, you can enable the write filter.
The write filter cache contents are not lost when you log off and on again (as the same or different user).
You can disable the write filter cache after the new logon and still retain the changes.
After you disable the write filter, all future writes during the current boot session are written to the flash
with no further caching until the computer is restarted. You can also enable/disable the write filter using
the command line.
NOTE:
Always enable the write filter after you have made all of your permanent changes.
NOTE:
Only an account with administrator privileges can enable, disable, or commit the enhanced
write filter.
Using the Enhanced Write Filter (EWF) command line
control utility
CAUTION:
Terminal Administrators should use Microsoft® Windows NT® file security to prevent
undesired usage of these commands.
CAUTION:
When using the
-commit
command, all of the temporary contents are permanently written to the flash memory.
NOTE:
Because the Enhanced Write Filter commands are executed on the next boot, you must restart
the computer for the command to take effect.
Windows® Embedded includes the EWF command line control utility. This utility enables you to issue
a set of commands to the EWF driver, report the status of each protected volume overlay, and report
the format of the overall EWF configurations.
Using the Enhanced Write Filter (EWF) command line control utility
9