Hi nazar,
i had followed these steps to restore a stock img i had found on these forums:
http://community.wd.com/t5/WD-My-Cloud/Rebuild-your-My-Cloud-or-upgrade-the-HDD-on-it/td-p/675109
when i restore the .img in ubuntu, i think it over writes the whole disk if im not mistaken.
Are you saying that with your method, in case i brick my drive, i have the .img made according to your steps, i could simply use “dd” again to write my .img to the two raid partition and that will,
1- restore my disk’s rootfs
2- It will not over write the data partitions etc…