Where is checkpoint file written running mdrun with MPI-threads

GROMACS version: 2021.5
GROMACS modification: Yes compiled with -DGMX_THREAD_MPI=ON -DMPI_C_COMPILER=mpicc

I am getting an error that has been seen before but to get troubleshooting help from my Cluster admins I need to know where the checkpoint files are being written/read to when running with mpirun. This is the error that happen when you probably do not have permissions to the folder on the cluster nodes:

Source file: src/gromacs/mdlib/mdoutf.cpp (line 463)
MPI rank:    0 (out of 16)

File input/output error:
Cannot rename checkpoint file; maybe you are out of disk space?

I run with in a directory on my own LSF storage so I have access here

mpirun --wdir . -np 16 /usr/local/gromacs/bin/gmx mdrun -ntmpi 16 -ntomp 6 -npme 4 -ntomp_pme 1 -deffnm md_0_1 -nb gpu

So my admins need to know where might mpi be reading and writing from?