Also known as defunct or dead process In simple words a Zombie process is one that is dead but is present in the systems process table. Ideally it should have been cleaned from the process table once it completed its jobexecution but for some reason its parent process didnt clean it up properly after the execution.
In a just Linux world a process notifies its parent process once it has completed its execution and has exited. Then the parent process would remove the process from process table. At this step if the parent process is unable to read the process status from its child the completed process it wont be able to remove the process from memory and thus the process being dead still continues to exist in the process table hence called a Zombie.
In order to kill a Zombie process we need to identify it first. The following command can be used to find zombie processes.