zombie process via 'top' command is not visible

junust · 04-07-2010, 03:25 AM

Hello,
I got indication of zombie process via top command

Code:

Tasks: 321 total,   1 running, 319 sleeping,   0 stopped,   1 zombie

BUT

I don't have 'Z' indication on 'Status' column

How could it possible to identify this process ?

Thx

EricTRA · 04-07-2010, 03:44 AM

Hi,

Maybe it's not shown because top doesn't list all on the screen. You can toggle ordering by status by pressing the 'w' character. Try that and see if the Z gets listed. Otherwise you can try using ps -aux which also shows the status of a process.

Kind regards,

Eric

junust · 04-07-2010, 04:29 AM

Actually, my problem was '-w Z' option on GREPing process

Code:

ps auxw | awk '{ print $8 " " $2 }' | grep -w Z

cause it look like

Code:

Zs 27844

But this was really helpful for me

Quote:

sometimes zombie processes have the string <defunct> at the end in the output of top

Code:

ps auxw | grep defunct

oracle  27844  0.1  0.0  0   0 ? Zs    Mar29  21:49 [oracle]<defunct>

EricTRA · 04-07-2010, 04:37 AM

Hello,

Correct! Below a quote from an article on TuxRadar.com:

Quote:

A defunct process is one that was started by another process (the parent), but has finished without the parent waiting for completion.
This can happen if the parent process has hung or crashed.

Defunct processes are also known as zombies, and listed with a 'Z' status in the output from ps. They're not quite as destructive as the living dead, as they consume almost no system resources, but on a system that's always turned on, such as a server, they can become equally distracting. The key to killing a defunct process is to first kill the parent, which will be listed in the output of ps with the addition of -l for long output. Parent processes can be identified under the PPID column, as opposed to the PID column for the process ID. These are identifiers attached to each process running on your system. They can be killed using another common shell command, kill -9, followed by the PPID. Obviously this will stop the parent task, so first make sure it's not essential. Once the parent process has been killed, the system init process should send the correct signal to the defunct process, which should terminate automatically.

Kind regards,

Eric

colucix · 04-07-2010, 06:16 AM

A little note: with ps you can choose the information to retrieve from processes using the -o option. In this way it's easy to parse them based on your needs. For example:

Code:

$ ps -eo pid,state,comm | awk '$2 == "Z"'
27844 Z oracle

junust · 04-07-2010, 08:55 AM

Good to know, thanks to all