Mox and ikt have limited disk space on the local drive on a compute node. Hence a program which creates temporary files explictly (e.g. C tmpfile() etc.) or implicitly (e.g. python package install, python multiprocessing, MPI etc.) may return an error about no disk space on /tmp. If this happens, you can set the TMPDIR variable to a different location and then run the program.
For example if your group is xyz and userid is abc:
Below links have more information about the use of /tmp for MPI: