parent process id of zombie process

[Shivkumar]

Hi,

Does all the zombie processes has parent process id of 1 ?

Thanks,
Shiv

[James R. Ferguson · Accepted solution]

Hi Shiv:

Stictly speaking a process with a parent pid (ppid) of one is an "orphan".

A zombie (prrocess) is a dead child process that has not yet been "reaped" by its parent. Reaping eliminates the zombie from the process table (which you will remember is limited in size by 'nproc'). This occurs when the parent process examines the child's exit status.

If proper coding techniques are followed, zombies are few and short-lived. The correct methods for 'fork'ing (creating) child processes add code for reaping by either paying attention to a SIGCHLD signal (signaling a child's end); or by explicitly setting SIGCHLD to IGNORE before forking a child.

It is a parent process's responsiblity to clean-up (reap) its dead children. The death of a parent before its children leads to 'orphan' processes where the orphan's parent becomes 'init'.

Regards!

...JRF...

[Arunvijai_4]

Hi Shiv,

Here are some good links to read,

http://aplawrence.com/SCOFAQ/FAQ_scotec6cantkill.html

http://en.wikipedia.org/wiki/Zombie_process


A zombie process is not the same as an orphan process. Orphan processes don't become zombie processes; instead, they are adopted by init (process ID 1), which waits on its children.


-Arun