[linux] How to kill zombie process

I launched my program in the foreground (a daemon program), and then I killed it with kill -9, but I get a zombie remaining and I m not able to kill it with kill -9. How to kill a zombie process?

If the zombie is a dead process (already killed), how I remove it from the output of ps aux?

root@OpenWrt:~# anyprogramd &
root@OpenWrt:~# ps aux | grep anyprogram
 1163 root      2552 S    anyprogramd
 1167 root      2552 S    anyprogramd
 1169 root      2552 S    anyprogramd
 1170 root      2552 S    anyprogramd
10101 root       944 S    grep anyprogram
root@OpenWrt:~# pidof anyprogramd
1170 1169 1167 1163
root@OpenWrt:~# kill -9 1170 1169 1167 1163
root@OpenWrt:~# ps aux |grep anyprogram
 1163 root         0 Z    [anyprogramd]
root@OpenWrt:~# kill -9 1163
root@OpenWrt:~# ps aux |grep anyprogram
 1163 root         0 Z    [anyprogramd]

I tried:

ps aux | grep -w Z   # returns the zombies pid
ps o ppid {returned pid from previous command}   # returns the parent
kill -1 {the parent id from previous command}

this will work :)

You can clean up a zombie process by killing its parent process with the following command:

kill -HUP $(ps -A -ostat,ppid | awk '{/[zZ]/{ print $2 }')

I tried

kill -9 $(ps -A -ostat,ppid | grep -e '[zZ]'| awk '{ print $2 }')

and it works for me.

Sometimes the parent ppid cannot be killed, hence kill the zombie pid

kill -9 $(ps -A -ostat,pid | awk '/[zZ]/{ print $2 }')

Found it at http://www.linuxquestions.org/questions/suse-novell-60/howto-kill-defunct-processes-574612/

2) Here a great tip from another user (Thxs Bill Dandreta): Sometimes

kill -9 <pid>

will not kill a process. Run

ps -xal

the 4th field is the parent process, kill all of a zombie's parents and the zombie dies!

Example

4 0 18581 31706 17 0 2664 1236 wait S ? 0:00 sh -c /usr/bin/gcc -fomit-frame-pointer -O -mfpmat
4 0 18582 18581 17 0 2064 828 wait S ? 0:00 /usr/i686-pc-linux-gnu/gcc-bin/3.3.6/gcc -fomit-fr
4 0 18583 18582 21 0 6684 3100 - R ? 0:00 /usr/lib/gcc-lib/i686-pc-linux-gnu/3.3.6/cc1 -quie

18581, 18582, 18583 are zombies -

kill -9 18581 18582 18583

has no effect.

kill -9 31706

removes the zombies.