https://linuxhandbook.com/system-has-not-been-booted-with-systemd/
Use
ps -p 1 -o comm=
command to see which system I'm using. Then change the command like the following.
(In my case, it was "init" after I typed the command)
Systemd commandSysvinit command
systemctl start service_name | service service_name start |
systemctl stop service_name | service service_name stop |
systemctl restart service_name | service service_name restart |
systemctl status service_name | service service_name status |
systemctl enable service_name | chkconfig service_name on |
systemctl disable service_name | chkconfig service_name off |