Take a service that keeps starting when you boot ubuntu, you can disable it via:
sudo update-rc.d nessusd disable
in my case, it was nessusd that I wanted to disable, you replace it by whichever service you want to stop from starting when you boot ubuntu.
That command will prevent it from starting again the next time you boot Ubuntu, but it won't stop the service running right now. If you also want to stop the service, type:
sudo service nessusd stop