Linux: Terminating a Zombie Process in Linux Environments

What is a Zombie Process:
It is a process that ended but not all of it is Immediately removed from the memory as its process descriptor stays in memory.

What should be the normal Behavior of a Process:
When a process ends, the process's status becomes EXIT_ZOMBIE and the process's parent is notified that its child process has died with the SIGCHLD signal.

The parent process is then supposed to run the wait() for the system call to read the dead process's exit status and other information. After wait() is called, the zombie process is removed from memory. This happens quickly, so you do not see zombie processes accumulating on your system. But in cases where we see several zombie processes accumulating, this is a situation where the program code is not efficient.

How to Find a Zombie Processes:
Running the command top
Running the command ps -ef | grep defunct
How to Terminate Accumulating Zombie Processes:
Most of the time, the zombie processes have the same parent process ID.

There are two methods to remove the process:

• Send the SIGCHLD signal to the parent process.

kill -s SIGCHLD <PPID>

kill -s SIGCHLD 2201

• Kill the zombie parent process

kill -9 <PPID>

kill -9 2201