Monday, January 25, 2016

How to kill a process in Linux if kill -9 has no effect



I imagine that kill -9 still just sends a signal to a process. If the process is not behaving well, I would imagine that kill -9 would have no effect. Indeed, today for the first time I saw kill -9 have no effect when sent to a stuck ruby process. So here is my question: Is there some harsher way to kill a process?



Answer



You have to reboot the machine. If kill -9 doesn't kill a process, that means it is stuck in the kernel. Unless you can figure out what it's stuck on and unstick it, there's nothing you can do. The reason it's stuck is that it is waiting for something and the logic necessary to cleanly stop waiting simply doesn't exist.



(The above assumes the process has already been reparented to init. Otherwise, its parent may be keeping it around. You may have to kill its parent.)


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