yum install ntp ntpdate
vi /etc/ntp.conf


允许查询的客户端网端
restrict 172.16.0.0 mask 255.255.0.0 nomodify notrap



chkconfig ntpd on
chkconfig ntpdate on
service ntpd start
service ntpdate start
iptables -I INPUT 行号 -m state --state NEW -m udp -p udp --dport 123 -j ACCEPT
service iptables save

在客户端测试
ntpq -p
ntpdate ntp.xxxx.com