disable/enable webmin

EXAMPLE 1

WEBMIN
Disable:
    sudo update-rc.d webmin disable
Enable:
    sudo update-rc.d webmin enable

Restart(full with button) server after command run

USERMIN
Disable: sudo update-rc.d usermin disable 
Enable: sudo update-rc.d usermin enable

EXAMPLE 2

Disable Autostart:
sudo systemctl disable usermin
sudo systemctl stop usermin

Prevent Future Restarts:
sudo mv /etc/usermin/miniserv.conf /etc/usermin/miniserv.conf.backup