On 2/11/2015 11:12 PM, David chen wrote: > Hi guys, > Thanks for your reply. > I originally used the following command to synchronize time: > ntpdate 192.168.0.191 > but got the error: ntpdate[16715]: the NTP socket is in use, exiting > So i used the way of stopping ntpd service. > Now I have known that using command "ntpdate -u 192.168.0.191" can solve the above error, and also know using ntpdate command is an improper way, i.e. should use ntpd service instead of ntpdate command. > But i have still a problem that why ntpdate command can cause backward clock? 192.168.0.191 is a valid ntpd server, its clock should not go backward, why the clock gotten by its client can go backwards? what ntp server is your ntpd synchronized to, and what is its time reference? if that 192.168.0.191 is your internal name server, you should edit /etc/ntp.conf and replace all teh server statements with one, 'server 192.168.0.191', then restart ntpd and get rid of your cron job. wait about an hour, and try `ntpstat` -- john r pierce 37N 122W somewhere on the middle of the left coast