When I type top in my terminal, I see a process with status "D" (Dead?) and one with "Z" (Zombie?). What does these two mean exactly? And how are they different?

I then want to kill them. So I type "kill (PID of those 2 processes)". But when I top again, I still see these 2 processes, with the same PID! I tried many times to kill them by using the "kill" command as well as typing "k" in top, but none can help me to kill the processes. What should I do? I just want those 2 processes being killed!

Thanks for any help offered!

Have you tried kill -9 [pid]? Some zombie processes cannot be killed until the system is rebooted.

I've tried many different signals including -s 9, -s 1 , -s 15, -s 6, -s 20.

But the process is still here. Whats the next step I can perform?

in my experience... reboot.

A 'D' process in top is not dead; it's a process that's using hardware (the 'D' stands for 'disk', but it could actually be using the network card or any number of other hardware devices instead).

All processes (either programs or threads) are started by another process, which is called its parent. If a process outlives its parent, then it is called a zombie. Zombies are not by definition a bad thing to have, but most programs will tidy up their child processes when the exit, so zombies are worth looking into if they hang around.


If kill -9 doesn't kill the process, nothing will.

It means that the process has some resources open, and won't close them, so the scheduler cannot remove it. This is most likely caused by a bug in some kernel module. Very occasionally, there are ways to forcibly remove resources, eg by unmounting a filesystem the program is holding open, but this relies on knowing what the resource is.

You can sometimes find relevant error messages in /var/log/messages, or by running dmesg, but sometimes not.

The best thing to do, unless you can find a way to diagnose the problem further, is to upgrade your kernel as soon as upgrades become available on your system.

If you do find more information, then report it to the maintainers of your distribution, and they will fix it in a later kernel release; by upgrading you are hoping that someone else has had the same problem (possibly with different symptoms) and tracked it down.

Thanks very much! Your replies help me to learn much more about the status of processes!