I sent the instructions to red_sun99 by email as well. I'm happy to help via chat/desktop sharing as well when required
The steps are as described below (all under Linux or Linux running in VirtualBox):
* Install java if you don't have it www.java.com
* Install the novacom driver, using Jason's Universal novacom installer (it will ask you to download a webos doctor file, you could select the 2.2.4 Verizon for Pre3). http://universal-novacom-installer.googlecode.com/files/Universal%20Novacom%20Installer.jar
* Install the Palm SDK from https://cdn.downloads.palm.com/sdkdownloads/18.104.22.1689/sdkBinaries/Palm_webOS_SDK-Win-2.1.0-519-x64.exe
In Linux Terminal run the following commands:
git clone git://git.webos-internals.org/tools/meta-doctor.git
when it gives "done", type:
cd meta-doctor (PRESS ENTER)
mkdir downloads (PRESS ENTER)
Get this file: http://downloads.help.palm.com/webosdoctor/rom/manta/p224r0d12192011/wdmantaverizon/webosdoctorp224mantaverizon.jar, it's a webos doctor 2.2.4 for a Verizon Pre3, it should work for this as we only need one file to boot the Pre3, save it in meta-doctor/downloads, rename it to webosdoctorp224manta-verizon-2.2.4.jar (not 100% sure about the filename, could also be webosdoctorp224manta-vzw-2.2.4.jar or something else)
Plug in your Pre3 (charge mode) and type:
make DEVICE=pre3 CARRIER=verizon memboot backup (PRESS ENTER)
You will get the uncompressing messages, then your Pre3 will reboot to enter a recovery mode, then you should get some unmounting messages, followed by Cloning messages, and at last some mounting messages. After that your Pre3 should reboot again
This should be more than enough.
There will be a directory inside the clones directory, there's the place where the backup will be.