Most Frequently Asked Questions.
Zombies are unreaped child processes.
They only eat a slot in the process table. Normally, this is not a problem, but it becomes troublesome on heavilly loaded machines running near the process limit, or in cases where a program spawns child processes often, but reaps rarely. This is usually a bug, and can lead to system crashes. When the parent exits, any unreaped processes will be reaped by init, but this can take a long time if the system is busy. Lots of zombies can be infuriating, because they can prevent you from running the commands you need to run to clean them up.