Note what MPI.lj says
You can install mpiexecjl with MPI.install_mpiexecjl() . The default destination directory is joinpath(DEPOT_PATH[1], "bin") , which usually translates to ~/.julia/bin , but check the value on your system.
Please do not hardwire this to /home/$USERNAME/.julia/bin
Use an environment variable, which means it is possible to use the Modules environment on HPC cyctems etc, to change where these are stored, or to have multiple Julia vversions co-existing on a system