simulation of multiple-processing on my Linux box
Linux boxes can always handle multi-processing (multiple programs), even multi-user (multiple users logged in at same time). You don't need rsh for that.
When you login, you are using a shell like Bash to interprete your commands.
rsh, or remote shell, is simply another shell that allows you to execute commands on a remote machine (rather than on your local one).
However, rsh is deprecated and ssh is often considered as a more secure alternative. ssh encrypts the connections between your machine and the remote machine. This makes sure no clear text passwords are sent over the network to the other machine.
So, my first suggestion would be to use ssh instead of rsh. It requires a little more setup (RSA keys, etc), but it's generally safer.
As for urpmi, I don't really use it, so I can't help you with that. But, judging from what you've posted, it seems that you were installing an rsh server, whereas there was already one on the system (the heimdal one).
Either remove the heimdal rshd (are you sure it's "removemedia" and not something like "remove"?) and install the other one afterwards, or stick to the heimdal rsh and discontinue the installation of the new one.
Please also give some more details as to what you want to accomplish exactly.