@bug11 My concern with integrating / relying on duplicati is:
1 - it’s dependancy on .NET or Mono
2 - it doesn’t appear to be that actively developed, last stable was 2013 !! but 2.0 coming apparently (2016)
(2 updates to dev release in 2015-16 from web page news)
3 - has it’s own “duplicity inspired!” protocol.
Does look active on GitHub though.
I think a better bet for Rockstor integration would be something that used a well known and multi program supported protocol / lower level program such as duplicity itself, or actively maintained wrappers such as duplicity-backup GPLv3. That way one would always have duplicity compatible archives and all the freedoms that come with that.
I would vote duplicati server mode as more of a Rock-on than something to build in proper.
Just my opinion though.
I thought duplicati use to be windows only when I last saw it, has it always been open-source and cross platform?