Starting multiple Cassandra nodes on the same machine involves setting loop back aliases and some configuration fiddling.
Lucky for you Sylvain Lebresne made this handy tool in python which does the job for you.
to run as a service you need a script like this http://www.bajb.net/2012/01/cassandra-service-script/
I haven’t tried this, I just run Cassandra in the foreground of a screen session.
How to configure linux service for Cassandra or start multiple Cassandra nodes from a single node?
Thanks very muh!