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 '13 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? – Garrett Albright Oct 23 '13 at 5:48
  • Are these the only two processes listed under Disk? Was nginx listed anywhere else and tagged as zombie? – CHM Oct 23 '13 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. – Garrett Albright Oct 24 '13 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 '13 at 0:22

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? – Garrett Albright Apr 17 '14 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. – bennettp123 Apr 30 '14 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 - Reinstate Monica Aug 3 '14 at 2:50

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