安装NTP环境
[root@VMPS ~]#yum install ntp ntpdate -y
root@VMPS etc]#cp ntp.conf ntp.conf.bak修改配置文件
[root@ ~]#: cp /etc/ntp.conf /etc/ntp.conf.bak # 备份
[root@ ~]#: vi /etc/ntp.conf
#Permit time synchronization with our time source, but do not
#permit the source to query or modify the service on this system.
trict 127.0.0.1
restrict -6 ::1
#Hosts on local network are less restricted.
#restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
restrict 192.168.95.0 mask 255.255.255.0 nomodify notrap #允许客户端从此处获取时间
restrict -6 ::1
#Use public servers from the pool.ntp.org project.
#Please consider joining the pool (http://www.pool.ntp.org/join.html).
#server 0.centos.pool.ntp.org iburst
#server 1.centos.pool.ntp.org iburst
#server 2.centos.pool.ntp.org iburst
#server 3.centos.pool.ntp.org iburst
server ntp1.aliyun.com
server time1.aliyun.com
server 127.127.1.1 #local clock
fudge 127.127.1.0 stratum 10 #当server无法连接时，使用本地时间作为标准
restrict ntp1.aliyun.com nomodify notrap noquery
restrict time1.aliyun.com nomodify notrap noquery添加 iptables 规则
[root@ ~]#: vi /etc/sysconfig/iptables
1 # Firewall configuration written by system-config-firewall
2 # Manual customization of this file is not recommended.
...
12 -A FORWARD -j REJECT --reject-with icmp-host-prohibited
13 -A INPUT -m state --state NEW -m udp -p udp --dport 123 -j ACCEPT # 添加于此
14 COMMIT配置参数简介:
ignore: 关闭所有 ntp 联机服务
nomodify: 客户端可通过服务器同步时间,但不能修改服务器的时间
notrap: 拒绝特殊的 ntpdq 捕获消息
noquery: 拒绝 btodq/ntpdc 查询
server: 添加上游 ntp 服务器
重启 iptables
[root@ ~]# /etc/init.d/iptables restart
开启 ntp 服务
[root@ ~]#service ntpd restart
[root@ ~]#chkconfig ntpd on
[root@ ~]#ntpdate -u 192.168.11.11 #手动同步时间`查看 ntp 服务器
[root@VMPS ~]# ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
120.25.115.20 10.137.53.7 2 u 55 64 377 39.367 -1.623 1.201
203.107.6.88 100.107.25.114 2 u 57 64 377 44.616 -1.263 1.011
*LOCAL(1) .LOCL. 5 l 17 64 377 0.000 0.000 0.000CLIENT配置
Linux client
[root@vmps ~]# vim /etc/ntp.conf
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
#server 0.centos.pool.ntp.org iburst
#server 1.centos.pool.ntp.org iburst
#server 2.centos.pool.ntp.org iburst
#server 3.centos.pool.ntp.org iburst
server 192.168.95.2 #设置ntpserver地址即可
保存退出
[root@vmps ~]#service ntpd restart
[root@vmps ~]#chkconfig ntpd on
cisco client
2960(config)#ntp server 192.168.95.2
2960(config)#clock timezone GMT 8
2960#show clock
15:05:12.545 GMT Fri Apr 24 2020
2960#show ntp status