Zombie process in Linux

Logging into one of my Linux boxes, I noticed I had a zombie process.

Welcome to Ubuntu 20.04.3 LTS (GNU/Linux 5.4.0-88-generic x86_64)

  => There is 1 zombie process.

A zombie process is

Processes marked are dead processes (so-called "zombies") that remain because their parent has not destroyed them properly. These processes will be destroyed by init(8) if the parent process exits.

A zombie process has a process state code of Z (how fitting), so we can filter on zombie processes this way:

ps axo stat=,pid= | grep "^Z"
Z     139262

To get just the PID of the zombie process:

ps axo stat=,pid= | grep "^Z" | awk '{ print $2 }'

To find the parent process:

pstree -p -s 139262

And finally, to kill the zombie's parent process:

kill 1896502


ps(1) - Linux man page https://linux.die.net/man/1/ps