So I have found myself in this situation more than once. I have a long running process running in a foreground, and i need to disconnect but dont want to loose the work already done by the process. The process is cpu intensive and thus is not responding to usual control+z. Here are steps you can take to force it into background and nohup it, making it possible to safely close the terminal window
open a new terminal window, find the process id of the long running process and do this
; suspend the process
kill -20
; or you can also use this
kill -stop
this should cause the process to be suspended in the original process. now you can background it. backgrounding it alone will not cause it continue running if the window is closed. you will need to disown it.
bg disown -h
the process is still suspended, so now resume it
; resume the process
kill -18
; or you can also use this
kill -cont
