Killing Zombie Processes

 
Zombie process

Zombie process is a dead process which not cleaned up properly so still has an entry to the process table. In fact when child process execution is completed but its not able to send the exit status to the parent process. Parent process still wait for the exist status from the child process. It is a good practice to clean/kill the defunct process.


1. How to find zombie process?

$ top -b1 -n1 | grep Z
or
$ ps aux | grep Z
or
$ ps aux | grep def

2. Find parent process of zombie process
$ ps -A -ostat,ppod | egrep '[zZ]' awk '{print $2}' | uniq | xargs ps -p
or
$ ps axo stat,ppid,pid,comm | grep -w defunct

3. send SIGCHLD process to parent process
$ kill -s SIGCHLD <PPID>
or
$ ps axo stat,ppid,pid,comm | awk '{ print $2}' | uniq | xargs kill -9
$ top -b1 -n1 | grep Z
or
kill -9 <PPID>

to kill

$ ps -af | grep def

kill the parent process

$ kill -9 <P-PID>