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I have Nginx installed; compiled via MacPorts, and configured to launch on start-up. When I go to the Disk tab of Activity Monitor after installing Mavericks, the nginx process(es) is listed with a kind of "Zombie," or sometimes "64 bit, Zombie." What does this mean?

Zombies on my Mac!

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    en.wikipedia.org/wiki/Zombie_process
    – CHM
    Oct 23, 2013 at 5:40
  • So no meaning relevant to disk usage, then? Then why is this column here and not, say, under the CPU and Memory tabs? Oct 23, 2013 at 5:48
  • Are these the only two processes listed under Disk? Was nginx listed anywhere else and tagged as zombie?
    – CHM
    Oct 23, 2013 at 6:06
  • For whatever reason, the Disk tab is the only place that has a "Kind" column like that, even though I think it would make more sense under CPU. In fact, wasn't that column there in 10.8? I seem to remember seeing it out Skype as still 32-bit before the upgrade as well. Oct 24, 2013 at 1:04
  • I'm sorry, can't help you on that one. I went from 10.6.8 to 10.9.
    – CHM
    Oct 25, 2013 at 0:22

1 Answer 1

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According to wikipedia, a zombie process is a process that has completed executing, but still has an entry in the process table. In other words, a zombie process has finished executing, but it hasn't been cleaned up yet.

When a process finishes, its return code needs to be returned to the parent process. Normally, this happens immediately, so you don't see the zombie process. However, sometimes, the parent process doesn't cooperate, and the zombie stays in the process table indefinitely.

If you want to get rid of a zombie process, you have three options:

  1. Wait. Hopefully it'll clear up on its own.
  2. Send a SIGCHLD to the zombie's parent. If it's behaving correctly, it'll fetch the return code of the zombie process, and the system can then reap the zombie process.
  3. Kill the parent process. When you kill a process, its children are adopted by init, which will clean everything up for you.
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    So why are these appearing under the "Disk" tab? Apr 17, 2014 at 16:35
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    Indeed. It does seem like an odd place for it. You can show the "Kind" column in the CPU/Memory tabs, but it's only shown by default in the "Disk" tab. As you mentioned above, the CPU and Memory tabs would be more appropriate places for them. Apr 30, 2014 at 9:36
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    @GarrettAlbright would you prefer it if processes arbitrarily hid themselves depending on the tab you're in?
    – Alexander
    Aug 3, 2014 at 2:50

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