Our application runs on Ubuntu 12.04 Precise. On this server, we have both ntpdate and ntp. How to enable and disable the NTP service on-demand? I tried # sudo update-rc.d -f ntp remove/default and # sudo update-rc.d ntp enable/disable commands, but when I reboot server the ntp service starts running! I suspect ntpdate is starting ntp service on reboot. I removed ntpdate package from one of my experimental server, then ntp didn't start on reboot after issuing: # update-rc.d ntp disable Is there a way to control this? or is there way to permanently disable ntpdate?