Netstat Zombies

[Tom Needs a Hat Mitchell]

On Mon, Mar 08, 2004 at 04:15:43AM -0800, edwarner99 at yahoo.com wrote:
> 
> I'm getting netstat zombies showing up from various
> programs like, mozilla 1.5, bash, sh, etc...
> 
> I searched bugzilla but couldn't find any reference.
> Any one experience this? I'm running the latest FC1
> kernel with all updates applied.

Can you give an example of what you are seeing and how 
you are seeing it. Also if you are trying to fix a problem.

I suspect that your zombies are simply normal processes that have yet
to deliver their exit status to their parent.  See the man pages for:

    wait                 (2)  - wait for process termination
    wait [builtins]      (1)  - bash built-in commands, see bash(1)
    wait3 [wait4]        (2)  - wait for process termination, BSD style
    wait4                (2)  - wait for process termination, BSD style
    waitpid [wait]       (2)  - wait for process termination
 and
    _Exit [_exit]        (2)  - terminate the current process
    _exit                (2)  - terminate the current process
    exit                 (3)  - End the application
    exit                 (3)  - cause normal program termination
    exit                 (n)  - End the application
    exit [builtins]      (1)  - bash built-in commands, see bash(1)

It is normal to see some zombie processes from time to time.  It is
not normal to see a thousand. If you or others background tasks with
"&" you may see these from other terminals only to have them vanish
when you look for them (with ps) on the terminal you launched them
from.  A side effect of ps is to cause a wait to be issued.  In this
case you are using netstat which may not have the same side effect.

Since bash is not the only shell it can be important to know what
shell is involved.  Some (sloppy) shell scripting styles can generate
lots of zombies.  Simply checking the exist status of subprocesses may
clean things up.  Scripts/subprocesses can be perl, php, sh, bash,
ksh, tcsh, csh, Netscape plug-in and mime handlers.....

Of interest, one of the things "init" does is to wait() (collect exit
status) on processes that it picks up for various reasons.  When you
logout, init may inherit the zombies and tidy up making problems with
user scripts invisible.


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