nohup running process:
Using zsh:
$ command_running_forever ^Z zsh: suspended command_running_forever $ bg [1] + continued command_running_forever $ jobs [1] + running command_running_forever $ disown %1 $ logout
(For bash use disown -h %1)
Send signals:
kill -20 PID kill -18 PID
(You still needs to disown before closing a terminal)