Type the following command to install ntp:
# yum install -y ntp
Turn on service:
# chkconfig ntpd on
Synchronize the system clock with 0.pool.ntp.org server:
# ntpdate pool.ntp.org
Start the NTP:
# /etc/init.d/ntpd start
安装和配置CentOS时钟同步服务,布布扣,bubuko.com
原文：http://www.cnblogs.com/sourceforge/p/centos-ntp.html