How to terminate a zombie process?

A zombie process is a process that has completed execution but still occupies an entry in the system's process table because its parent process has not yet read its exit status using the wait() system call.

To terminate a zombie process, the first step is to terminate its parent process. When the parent process terminates, the zombie process will be adopted by the init process (or its modern equivalent, such as systemd), which will perform the necessary wait() system call and remove the zombie from the process table.

Steps to terminate a zombie process:

Identify the PPID (parent process ID) of the zombie process.
```
# Find zombie processes and their PPID
ps aux | awk '{ print $8, $2, $4 }' | grep Z
```
The output will be approximately like this: Z 1234 5678, where 1234 is the PID of the zombie process, and 5678 is the PPID of the parent process.
Terminate the parent process. Use the PID of the parent process obtained in the previous step.
```
# Forcefully terminate the parent process
kill -9 <PPID_of_parent_process>
```
Use the SIGKILL (-9) signal to ensure the parent process is terminated, especially if the normal SIGTERM signal does not work.

After the parent process terminates, the system will automatically remove the zombie process. In rare cases, if the zombie process issue is caused by a deep kernel problem, a server reboot may be necessary.