Operation and Maintenance
Linux Operation and Maintenance
What are the methods to achieve time synchronization in Linux?What are the methods to achieve time synchronization in Linux?
Linux实现时间同步的方法的有两种,分别是:1、使用ntpdate从时间服务器来更新时间,不需要自己做任何配置;2、使用ntp来搭建自己的时间服务器。

【推荐课程:Linux系统】
由于硬件的原因,机器或多或少的跟标准时间对不上,误差几秒到几分钟不等。对于服务器来说时间不准会有很多麻烦。例如支付的时候,无法下单,游戏无法登录等。接下来将在文章中为大家分享Linux系统中如何实现时间同步,希望对大家有所帮助
方法一:用ntpdate从时间服务器更新时间
如果linux系统没有ntpdate这个命令,可以输入以下代码进行安装
yum install ntp
安装完了之后,你不要做什么配置,也不需要,直接测试一下
vi /etc/ntp.conf add below: server 1.cn.pool.ntp.org server 3.asia.pool.ntp.org server 2.asia.pool.ntp.org
restart service and sync the time
[root@localhost ~]# ntpdate time.nist.gov 22 Oct 21:11:43 ntpdate[5014]: adjust time server 207.200.81.113 offset -0.018788 sec
如果显示上面的内容说明同步成功了,然后在crontab里面加上以下内容。
*/10 * * * * ntpdate time.nist.gov #域名或IP
每隔十分钟同步一次。推荐几个时间服务器。
time.nist.gov
time.nuri.net
0.asia.pool.ntp.org
1.asia.pool.ntp.org
2.asia.pool.ntp.org
3.asia.pool.ntp.org
方法二、用ntp搭建自己的时间服务器
上面是利用别人的时间服务器来同步时间,这些时间服务器都是比较权威的。当我们自己搭建时间服务器就不用crontab来定时去跑。
1、安装时间服务器ntp
yum install ntp
2、配置ntp
[root@localhost ~]# cat /etc/ntp.conf |awk '{if($0 !~ /^$/ && $0 !~ /^#/) {print $0}}'
restrict default ignore //默认不允许修改或者查询ntp,并且不接收特殊封包
restrict 127.0.0.1 //给于本机所有权限
restrict 192.168.1.0 mask 255.255.255.0 notrap nomodify //给于局域网机的机器有同步时间的权限
server time.nist.gov prefer //设置时间服务器,加prefer表示优先
server 0.asia.pool.ntp.org
server 1.asia.pool.ntp.org
server 2.asia.pool.ntp.org
server 127.127.1.0 # local clock
fudge 127.127.1.0 stratum 10
driftfile /var/lib/ntp/drift
keys /etc/ntp/keys3、启动 ntp
[root@localhost ~]# /etc/init.d/ntpd start
4、查看并测试
[root@localhost ~]# netstat -upnl |grep ntpd //查看时程 [root@localhost ~]# ntpq -pn //查看同步的服务器IP remote refid st t when poll reach delay offset jitter ============================================================================== 50.77.217.185 .INIT. 16 u - 64 0 0.000 0.000 0.000 202.90.158.4 .INIT. 16 u - 64 0 0.000 0.000 0.000 202.71.100.89 .INIT. 16 u - 64 0 0.000 0.000 0.000 202.134.1.10 .INIT. 16 u - 64 0 0.000 0.000 0.000 *127.127.1.0 .LOCL. 10 l 18 64 377 0.000 0.000 0.001 [root@localhost ~]# ntpstat //同步的结果 synchronised to local net at stratum 11 time correct to within 12 ms polling server every 512 s
remote:即NTP主机的IP或主机名称。注意最左边的符号,如果由“+”则代表目前正在作用钟的上层NTP,如果是“*”则表示也有连上线,不过是作为次要联机的NTP主机。
refid:参考的上一层NTP主机的地址
st:即stratum阶层
when:几秒前曾做过时间同步更新的操作
poll:下次更新在几秒之后
reach:已经向上层NTP服务器要求更新的次数
delay:网络传输过程钟延迟的时间
offset:时间补偿的结果
jitter:Linux系统时间与BIOS硬件时间的差异时间
推荐第一种方法,虽然搭建个时间服务器,比较简单的,但是我觉得没有这个必要。如果用别人的时间服务器,每隔10分钟同步一次,可以精确到毫秒。
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