I ran a R console on our server, and the process took much longer time than I expected. Thus I was trying close it by ctrl+z, it didn't work. Finally I just closed the terminal. But the process is still there when I check with top commands. I used kill, but won't kill the process. The top command output: PID   USER     PR   NI  VIRT    RES    SHR  S  %CPU %MEM  TIME+ COMMAND     27448 zhenyang  20   0 20.133g 0.020t 3.840g R 100.0 21.3  72:00.06 R I checked the website and someone says it might be ctrl+z put the process in background, but fg command won't work. Anyone help? 
can't kill a process running on server
kill