Try This...

Run bash from GRUB

https://unix.stackexchange.com/questions/34462/why-does-linux-allow-init-bin-bash

add rw init=/bin/bash

Fork bomb (bash version)

https://unix.stackexchange.com/questions/283496/why-do-these-bash-fork-bombs-work-differently-and-what-is-the-significance-of
https://askubuntu.com/questions/159491/why-did-the-command-make-my-system-lag-so-badly-i-had-to-reboot

CAUTION

set user limits first with

user01@machine01 ~ $ ulimit -u
31104
user01@machine01 ~ $ ulimit -u 10
user01@machine01 ~ $ ulimit -u
10

:(){ : | : & }; :

:() is a function name with the open and close parenthesis representing no parameters. The body of this function is within the braces {}.
: | : is a recursive call since : is the name of the function. The function gets called twice and is piping input from one call to the other.
& backgrounds the previous function call so that it will not die.
; finishes the function declaration.
: Calls the function just defined.

Urgent remediation

Alt+SysRq+K will stop all processes on current tty.
Alt+SysRq+RK on X server terminal

To Do’s

Mount initrd and investigate content…

investgate kthread… (the father of all threads…)