Comment 10 for bug 403109

I'm having the same problem. Deja-dup kept on failing to backup saying that there was not enough space left, while my backup hard drive contains more than enough free space (808GB versus 461GB needed to backup). It only became apparent to me that deja-dup meant that my main hard drive was out of disk space when Ubuntu gave my a warning saying that my hard disk was nearly full. The deja-dup .cache folder took up 26GB.

It would indeed be nice if a more descriptive error message was displayed and/or if deja-dup indicates how much disk space it needs on the main hard drive before starting the backup. I'll use Dražen Lučanin's workaround for now.