Dear forum members,
seems I bricked the EX2 with a wrong network configuration. The device is not available via network anymore, neither webinterface nor ssh. Also the router doesn’t show it as connected to the network. I tried to reset the EX2 pressing the reset button on its back (5s and 40s, as somewhere recommended in the forum), but it doesn’t help either. Is there any other way to restore the factory firmware?
Anyway, I tried some things on my own: I removed the hard disks from the EX2 and put it into my PC. I managed to create the RAID and mount the second raid (data) partition, it looks well. However, I wasn’t able to mount the first raid partition. I think the filesystem isn’t recognized properly. What kind of filesystem is it, is there a proprietary filesystem used? As far as I understood, this partition contains the system partition. In other threads  I read it is possible to restore the original firmware by pasting the firmware image into the first partition using dd. But this hint refers mainly to the MBL, whose firmware really contains a disk image (i.e. rootfs.img) with a size of ~2GB. Unfortunately the EX2 firmware available for download doesn’t contain such an image, since it contains just a single big executable/binary.
Next thing I tried was to build the EX2 firmware from source  by myself: (of course) it doesn’t build an image of the partition but a ‘WD-NAS-firmware’ executable, and (!) an ‘image.cfs’ file. Is it possible to restore the factory firmware by dd’ing this image.cfs on the first partition? As image is too small for the original partition image (~93M vs. ~2GB), can someone tell how to make this thing ‘fitting’.
Another alternative is to use the very original EX2 firmware image for dd. Maybe someone can point me to the place where I can get such an image from, or provide one? Or, at least tell me I’m totally off the track… Any help is really appreciated!