I want to learn from the output from command ps
usr@host:~$ ps -ef | head -5
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 16:43 ? 00:00:04 /sbin/init splash
root 2 0 0 16:43 ? 00:00:00 [kthreadd]
root 3 2 0 16:43 ? 00:00:00 [rcu_gp]
root 4 2 0 16:43 ? 00:00:00 [rcu_par_gp]
/sbin/init
is not hard to follow, utility init
start a big bang to splash elements, it is a command.
when it comes to [kthreadd], [rcu_gp], I do not find such utilities or command from the entire file system.
Are they commands?