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Date:      Wed, 12 Jun 2002 15:29:30 -0500
From:      "Jack L. Stone" <jackstone@sage-one.net>
To:        Layder <layder@ukr.net>, freebsd-stable@FreeBSD.ORG
Subject:   Re: Zombie processes
Message-ID:  <3.0.5.32.20020612152930.01044510@mail.sage-one.net>
In-Reply-To: <20020612225810.D2721-100000@cyanide.pro>

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At 11:00 PM 6.12.2002 +0300, Layder wrote:
>Processes in my box never gone. They become zombies and their
>quantity increased with time and than locks the system talking that
>cannot fork process. What can I do?
>My system is Celeron 500 with 64 MB RAM
>
Here was the advice I received a couple of weeks ago:
  $ ps alx | grep Z
   UID   PID  PPID CPU PRI NI   VSZ  RSS WCHAN  STAT  TT       TIME COMMAND
   1004 82075  6901 295  96  0     0    0 -      Z+    p5    0:00.00  (sh)

See the Z under STAT?  That show that the process is a zombie.

 and what does it mean...????

It means that the process has died, but hasn't been buried yet.  The
trouble with zombies is that you can't kill them, because they're
already dead :-) First the parent process (6901 in this example) must
wait for it and collect its status.

You have two choices here: 

1.  Ignore it, it's not holding on to too many resources.
2.  Kill the parent.  That may or may not be a good idea.  For
    example, in this case,

    $ ps lp6901
      UID   PID  PPID CPU PRI NI   VSZ  RSS WCHAN  STAT  TT       TIME COMMAND
     1004  6901  6620 127  20  0   848  102 opause S+    p5    5:42.68
observe dates

    This is a process I have on my machine which shows the dates
    around the world every 2 seconds.  Sure, I can kill it and restart
    it, but is there any point?  In this case, if I go back and look
    for that zombie, I'll find it's already gone: I've just caught a
    zombie in the stage before being buried.  In other cases, and
    especially if the program is causing lots of zombies, you may want
    to stop it.

Best regards,
Jack L. Stone,
Administrator

SageOne Net
http://www.sage-one.net
jackstone@sage-one.net

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