Zombie Process
A zombie, or defunct, process is a process that has terminated, but its parent process has not taken it out of the process table with the wait() family of system calls. This typically happens when a program forks/execs another program, but then doesn’t reap it properly. The easiest way to write the parent to properly reap its children is to setup a signal handler for SIGCHLD that calls wait().
See the man pages on your local system for signal and wait(2).
Zombie and defunct states of a process are different things. Zombie is created when a child dies and parent didn’t call wait. Defunct is created when parent dies before the child finishes.
Defunct processes can’t be killed since they are already dead. To make them disappear you have to kill their parent process…
It’s not possible to kill defunct processes.
A good way to kill lists of processes is:
$ ps axf | grep name-of-process | grep -v -grep | awk '{print "kill -9 ",$1}' | sh
