I've tried clonezilla live cd, and I got an image but in a kind of folder. I would need an .img file or something because afterwards I will use some images together, but that is other story.
I also used
dd if=/dev/sda of=~/disk1.img but it doesn't finish the image because the disk has 500GB and the image just about 100MB the first time and 2GB the second time, so I think that stops before finish for any reason I'm not aware of.
Do you know any way of doing an image of a disk?