Skip to main content

Linux: How To Identify a Zombie/Defunct Process and Clean It

Every process has a parent process and the parent processes are responsible for creating (forking) child processes and cleaning them from the process table after they finished their execution. When a process finishes its execution it leaves an exit status to be sent to the parent process, then it becomes a zombie.

In some cases, a process can not be cleaned from the Linux OS process table properly after finishing the execution. An increasing number of defunct processes may lead to a system outage because the size of the process table is limited.

If a zombie process exists, top command should show the number of them on the top/right corner of the screen:

top - 11:24:49 up 3 days, 18:23, 1 user, load average: 7.04, 6.72, 6.39
Tasks: 304 total, 3 running, 297 sleeping, 0 stopped, 4 zombie

To find a defunct process ps command can be used:

# ps -ef |grep -v grep |grep "Z\|defunct"
102 1485669 2953018 0 07:07 ? 00:00:00 [ssh] <defunct>

To clean it, SIGCHLD signal should be sent to the parent process.

# kill -s SIGCHLD 2953018

if sending a SIGCHLD signal doesn't work, you should kill/restart the parent process.

# kill -9 2953018


Popular posts from this blog

Creating Multiple VLANs over Bonding Interfaces with Proper Routing on a Centos Linux Host

In this post, I am going to explain configuring multiple VLANs on a bond interface. First and foremost, I would like to describe the environment and give details of the infrastructure. The server has 4 Ethernet links to a layer 3 switch with names: enp3s0f0, enp3s0f1, enp4s0f0, enp4s0f1 There are two bond interfaces both configured as active-backup bond0, bond1 enp4s0f0 and enp4s0f1 interfaces are bonded as bond0. Bond0 is for making ssh connections and management only so corresponding switch ports are not configured in trunk mode. enp3s0f0 and enp3s0f1 interfaces are bonded as bond1. Bond1 is for data and corresponding switch ports are configured in trunk mode. Bond0 is the default gateway for the server and has IP address Bond1 has three subinterfaces with VLAN 4, 36, 41. IP addresses are,, respectively. Proper communication with other servers on the network we should use routing tables. There are three

PowerShell Script for Switching Between Multiple Windows

Windows PowerShell has strong capabilities. I have a separate computer with a big lcd screen in which I am watching regularly some web based monitoring applications. So I need those application windows switch between on a timely basis. Then I wrote this simple powershell script to achieve this. You can change it according to your needs.