Solaris

Many of you are not understanding. jlliagre is correct but not getting through somehow.

A zombie process merely clogs up a process slot in the kernel process entry table. It has no resources tied up. It is waiting to return status to a parent (called reaping), and the parent has not called wait(). Some negligent parents never call wait.

If a parent exits before calling wait then the init process reaps the orphaned child process. It may spend a short while as a zombie.

[opinion]

I personally think the guy who created the idea of calling those processes a 'zombie' was creative and totally misguided. We all know that somehow zombies are evil. Therefore you have to get rid of them They must be vermin. Kill them all!

This is a case of the name providing non-existent negative attributes to something.
Zombies are okay. They are not as evil as the name implies.

[/opinion]

What you really need to do: fix the bad programming that creates them. Or hire good programmers.

Zombies DO NOT respond to signals because they lack the process context to do so.
Kill -9 sends a signal.

Commands like preap just remove them from the internal kernel table by forcing the naughty parent process to call wait. Plus, it is OKAY to have a few zombies. It gives some programmers a chance to worry about something harmless, and bug the sysadmin.
Sysadmins love to be bugged by users.

When you have loads of zombies and they persist for days, it is time to rewrite code, or spend all day calling preap (on Solaris).

I am employed, with a mortgage...and an endless commute...another form of zombie. Not necessarily evil...but unable to respond to signals in many, many ways. (Just ask the wife if my ears work...)

Very good explanation, jim_mcnamara. Perhaps we've met another form of the useless use of cat? Killing the dead?

Good article thanks.But I dont say to jlliagre is not correct ?

Not sure what means I'm not getting through. As I wrote, two zombies processes isn't a problem. They won't hurt the process table which has 32000 entries on Solaris and can be raised up to 999999. The only issue is cosmetic. I.e. zombies pollute ps and similar commands output. Reaping can fix that but the real issue is parent processes not handling their child's death, as I wrote too.