Date: Fri, 31 May 2002 13:48:04 +0930 From: Greg 'groggy' Lehey <grog@FreeBSD.org> To: "Jack L. Stone" <jackstone@sage-one.net> Cc: freebsd-questions@freebsd.org Subject: Re: What Zombie? Message-ID: <20020531134804.D6654@wantadilla.lemis.com> In-Reply-To: <3.0.5.32.20020530223305.01c537a8@mail.sage-one.net> References: <3.0.5.32.20020530223305.01c537a8@mail.sage-one.net>
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On Thursday, 30 May 2002 at 22:33:05 -0500, Jack L. Stone wrote:
> 4.5-RELEASE
>
> I just ran dd on two 40GB to backup the main HD-1 to HD-2. While running
> top to watch the dd, I noticed a "zombie" appeared listed at the summary in
> of processes. Got 54 processes, 1 running and that 1 zombie. Never seen it
> before. How can I find that zombie
$ 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.
Greg
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