First, as a reminder, here is what the instructor's nbgrader_config.py file looks like:
In [ ]:
%%bash
cat nbgrader_config.py
After students have submitted their assignments, the instructor can view what has been submitted with nbgrader list --inbound:
In [ ]:
%%bash
nbgrader list --inbound
The instructor can then collect all submitted assignments with nbgrader collect and passing the name of the assignment (and as with the other nbgrader commands for instructors, this must be run from the root of the course directory):
In [ ]:
%%bash
nbgrader collect "Problem Set 1"
This will copy the student submissions to the submitted folder in a way that is automatically compatible with nbgrader autograde:
In [ ]:
%%bash
ls -l submitted
Note that there should only ever be one instructor who runs the nbgrader release and nbgrader collect commands (and there should probably only be one instructor -- the same instructor -- who runs nbgrader assign, nbgrader autograde and nbgrader formgrade as well). However this does not mean that only one instructor can do the grading, it just means that only one instructor manages the assignment files. Other instructors can still perform grading by accessing the formgrader URL.