Interesting. Thanks for the clarification. I don't know if /usr/lib/hue is still a good idea for user code but like you said it is the Hue home directory. Maybe running as root makes more sense? On HDFS /user/root may already exist? The downside being that logging into Hue you won't be able to see the input/output files.

The sandbox in general makes running custom MapReduce interesting because of the users and groups.