Comment 3 for bug 1895353

Try this:
# ulimit -n 65536
# duplicity ...your options...

If that works, set it globally via one of the solutions on the net. Google "linux too many file handles". I am not familiar with your distro, so find the solution closest.

Also, so I can rule out one problem I've encountered from downstream distros, please check the duplicity directory for the file 'gpginterface.py', then check line 696 for threaded_waitpid(). I had to modify the original to harvest the fileid's of completed processes. Some distro's will make the mods back to the original in error, something I've never understood.