I need to find a way of controlling the rsa key used when open-mpi uses ssh to access hosts.  By default, ssh uses the

    ~/.ssh/id_rsa

However, I need to set the key used without messing around with users' .ssh directories.  It appears that in a default installation of open-mpi, ~/.ssh is specfied is mca_base_param_file_path.  Can I change the ssh directory used by setting this mca param? Or is there some other way of specifying the id_rsa file (other than changing ssh config files).

More generally, is there anything posted that states in detail what mca_base_param_file_path controls? 

I've found a reference to it in the FAQ: "The MCA parameter (mca_base_param_file_path) specifies the path to search for AMCA files with relative paths. By default this is $SYSCONFDIR/amca-param-sets/:$CWD."   From this description, it doesn't like setting mca_base_param_file_path will solve my problem.

thanks