Dealing with Zombie Process on Linux
I am going to start by defining what is a Zombie Process
Well a Zombie Process is the actually the state of the process when the child dies before the parent process. In this case the structural information of the process is kept in the process table.
Danger !!!
Processes in Zombie State don’t use up any system resources. (Actually, each one uses a very tiny amount of system memory to store its process descriptor.) However, each zombie process retains its process ID (PID). If zombies are accumulating at a very quick rate the entire pool of available PIDs will eventually become assigned to zombie processes, preventing other processes from launching.
In any case, a few zombie processes hanging around are no problem – although they do indicate a bug with their parent process on your system.
How to remove or get rid of Zombie Processes ?
You can't kill a Zombie Process the normal way as it does not exist.
One way is by sending the SIGCHLD signal to the parent process. This signal tells the parent process to execute the wait() system call and clean up its zombie children.
Example of the command:
kill -s SIGCHLD 
But also we can
Example of the command: (ps aux | grep -w Zs)
[root@host]# ps aux | grep -w Zs
oracle 3142 0.0 0.0 0 0 ? Zs Jan05 0:00 [Oracle Tutorials]
oracle 3219 0.0 0.0 0 0 ? Zs Jan05 0:00 [Oracle Tutorials]
root 15129 0.0 0.0 61252 760 pts/4 S+ 12:36 0:00 grep -w Zs
oracle 17112 0.0 0.0 0 0 ? Zs 11:29 0:00 [sh]
oracle 17387 0.0 0.0 0 0 ? Zs 11:29 0:00 [sh]
oracle 30994 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 31303 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 31737 0.0 0.0 0 0 ? Zs Jan04 0:00 [sh]
oracle 31826 0.0 0.0 0 0 ? Zs Jan04 0:00 [sh]
oracle 31861 0.0 0.0 0 0 ? Zs Jan04 0:00 [sh]
oracle 31872 0.0 0.0 0 0 ? Zs Jan04 0:00 [sh]
oracle 32056 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 32062 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 47086 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 47316 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 47321 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 47481 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 47570 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 47582 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 47649 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 48010 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 48111 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 48196 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 48685 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 49630 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 49724 0.0 0.0 0 0 ? Zs Jan04 0:00 [Oracle Tutorials]
oracle 83350 0.0 0.0 0 0 ? Zs Jan05 0:00 [Oracle Tutorials]
oracle 83395 0.0 0.0 0 0 ? Zs Jan05 0:00 [Oracle Tutorials]
oracle 86877 0.0 0.0 0 0 ? Zs 09:12 0:00 [Oracle Tutorials]
oracle 87168 0.0 0.0 0 0 ? Zs 09:12 0:00 [Oracle Tutorials]
oracle 87338 0.0 0.0 0 0 ? Zs 09:12 0:00 [Oracle Tutorials]
oracle 87811 0.0 0.0 0 0 ? Zs 09:13 0:00 [Oracle Tutorials]
oracle 87994 0.0 0.0 0 0 ? Zs 09:13 0:00 [Oracle Tutorials]
oracle 89624 0.0 0.0 0 0 ? Zs 09:15 0:00 [Oracle Tutorials]
oracle 89836 0.0 0.0 0 0 ? Zs 09:15 0:00 [Oracle Tutorials]
oracle 90227 0.0 0.0 0 0 ? Zs 09:15 0:00 [Oracle Tutorials]
oracle 90458 0.0 0.0 0 0 ? Zs 09:16 0:00 [Oracle Tutorials]
oracle 92550 0.0 0.0 0 0 ? Zs 09:19 0:00 [Oracle Tutorials]
oracle 92554 0.0 0.0 0 0 ? Zs 09:19 0:00 [Oracle Tutorials]
oracle 99670 0.0 0.0 0 0 ? Zs 11:13 0:00 [Oracle Tutorials]
