Bypass EWF ?

Zorro_X · 08-14-2007, 04:28 PM

Hello,
I'm using EWF to protect CF disk. That works quite well ! But for debuggin purposes and persistent data of my embedded application, I need to bypass EWF to write 1 or 2 files (debug log & persistent data files).
I wonder if there is a way to do it using windows API. Some kind of "ewf commit and disable" command without doing a nasty "system" call ?
I'm using C++ (so using the C API).

In another hand, I know that you usually do partitionning of the CF and don't protect the partition where you want to write. I can do that, but it will be more interesting for me if i can bypass EWF.

Thank you in advance for your answers,

SFiorito · 08-14-2007, 07:50 PM

well, you can use EwfCommitFile in the EWF API but it only works on files that don't change in size. You can also search the OS forums for an old thread of mine where I describe creating a fixed size virtual disk that you can then write any number of files into. Since the virtual disk is fixed size you can then commit it and maintain state.

Otherwise you can use FBWF File Based Write Filter, but I haven't gotten around to write a tutorial for that.

Zorro_X · 08-15-2007, 01:23 AM

Thank you, i'll investigate those ways.

tn6478 · 08-15-2007, 12:54 PM

Quote: Originally Posted by SFiorito

well, you can use EwfCommitFile in the EWF API but it only works on files that don't change in size. You can also search the OS forums for an old thread of mine where I describe creating a fixed size virtual disk that you can then write any number of files into. Since the virtual disk is fixed size you can then commit it and maintain state.

Otherwise you can use FBWF File Based Write Filter, but I haven't gotten around to write a tutorial for that.

How do you excute those files to mount and unmount at shutdown and startup. Also if the files change the partition get screw?

erie · 08-27-2007, 10:04 PM

how about this?
http://msdn2.microsoft.com/en-us/library/ms912855.aspx

I dont know C but I think this might be helpfull.

erie · 08-27-2007, 10:17 PM

tn6478, you dont have to use code to persist data. I have used the Registry Filter component and it is easy to work with http://msdn2.microsoft.com/en-us/library/aa940857.aspx

A trick I use on my work images is to use a registry key to keep all the settings for the custom apps. If you want debug data, write custom events to the system event log. Next configure the registry filter to persist the event logs.

SFiorito · 08-28-2007, 05:14 PM

If you look at this thread: http://www.mp3car.com/vbulletin/winn...bling-ewf.html

You can download some tools I wrote to mount/unmount SDI files and commit the file to the EWF disk.

This site explains setting up Startup/Shutdown scripts using XP Group Policy: http://www.microsoft.com/resources/d....mspx?mfr=true

The SDI will not change in size so it will not corrupt the volume, but the contents can change with no problem.

stric · 08-29-2007, 03:11 AM

So if user would use one SDI partition on CF for settings, error logs, and other changable files ... how would that affect the life of CF card (I understand it would shorten it

, but how much).

What if you have 1GB SDI partition also for cam videos, updates and so on? What would that mean for CF's lifetime?

SFiorito · 08-29-2007, 07:16 AM

Clearly it wouldn't help it, but the the writes would happen once at a time instead of continuously. Also, if your system is set to sleep and only shutdown after a prolonged amount of time you may only write the SDI once or twice a day.

Obviously this isn't the best option, but if you have no other choice then it's a good alternative.