I don't know, please tell me how can I know that?
this will give you a bunch of statistics about the system, including that's running and how much CPU it is taking.
to find out how many processes of nodejs are running i would recommend using#> ps aux |grep node
this will spit our information about all processes that have "node" in their command line. you'll probably get a few false positives but you should be able to identify how many of those are nodebb easily enough.