I use Déjà Dup to backup my Fedora 18 desktop. Déjà Dup being a graphical front-end to duplicity.
Recently these backups ceased to work, with Déjà Dup complaining that it didn't have sufficient space to continue. A quick investigation showed almost all of the 4GB of /tmp was being utilized. Obviously a deep flaw in the design of Déjà Dup, but in the meantime I needed to get the backups working once again.
What needs to be done is to set the variable TMPDIR to somewhere with more free space and then run Déjà Dup. In my case running this from the terminal was enough to get the backup working:
TMPDIR=/data/tmp /usr/bin/deja-dup --backup
For a more permanent solution put the TMPDIR variable in .profile