lsof -wni tcp:3000
Then you should see the ruby process and you can run
kill -9 processid
you should be good to run the process now
rails s thin
running multiple processes doesn't seem like a good idea and from what i've read many people agree. I've noticed many memory leaks with rails unfortunately so I couldn't imagine having two processes running. I know with one overtime my page refreshes increasingly become slower because of the data being stored on memory.