CONFIGURING THE NTP CLIENT
++++++++++++++++++++++++

1) #yum install ntp **to get latest ntp**
2)#chkconfig --level 235 ntpd on **to let the ntp started upon boot of the OS**
3)#ntpdate 192.168.10.xx (my master ntp server)
4)#service ntpd start

please refer to this link:
http://www.thewebhostinghero.com/tutorials/synchronizing-system-clock-ntp.html

CONFIGURING THE NTP SERVER
++++++++++++++++++++++++

Please refer to this link:
http://www.cyberciti.biz/faq/rhel-fedora-centos-configure-ntp-client-server/

Thanks for the both links which help me much!