OpenMPI MCA parameters can be set in several ways. Some MCA parameters configure hardware, while other configure warnings. Depending on whether the parameters need to be per-user, per-hardware, etc. it may be useful to set some in a file, and others in the environment variables, and still others on the command line.
OpenMPI looks for a file at ~/.openmpi/mca-params.conf to set MCA parameters. The environment variables have a higher priority, and the command line has the highest priority as is intuitive.
The mca-params.conf syntax is like:
btl_openib_warn_no_device_params_found = 0
The environment variables would be set in ~/.bashrc or similar like: