ntp服务器搭建

/etc/ntp.conf

#使用阿里云NTP服务器，建议使用多个，距离近的、不同地区的。

server 120.25.115.19
server 182.92.12.11

#设置使用本地时间作为时间源，将本地源的stratum设为8，如果大于10的话windows客户端貌似会放弃同步。
server 127.127.1.0
fudge 127.127.1.0 stratum 8

生产配置

[root@sisap ~]# grep -Ev "^[#]" /etc/ntp.conf

driftfile /var/lib/ntp/drift

restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

restrict 127.0.0.1
restrict -6 ::1

server 120.25.115.19 prefer
server 182.92.12.11

server 127.127.1.0
fudge 127.127.1.0 stratum 8

includefile /etc/ntp/crypto/pw

keys /etc/ntp/keys

logfile /var/log/ntp.log

常用命令

[root@locahost log]# ntpq -p

remote refid st t when poll reach delay offset jitter
==============================================================================
120.25.115.19 .INIT. 16 u - 64 0 0.000 0.000 0.000
182.92.12.11 .INIT. 16 u - 64 0 0.000 0.000 0.000
*LOCAL(0) .LOCL. 8 l 11 64 17 0.000 0.000 0.000

调试：

[root@localhost local]# ntpdate -d 10.1.1.10
25 May 14:34:38 ntpdate[11180]: ntpdate 4.2.6p5@1.2349-o Fri Jul 24 10:56:18 UTC 2015 (1)
Looking for host 10.1.1.10 and service ntp
host found : wat.gaad.com
transmit(10.1.1.10)
receive(10.1.1.10)
transmit(10.1.1.10)
receive(10.1.1.10)
transmit(10.1.1.10)
receive(10.1.1.10)
transmit(10.1.1.10)
receive(10.1.1.10)
10.1.1.10: Server dropped: strata too high
server 10.1.1.10, port 123
stratum 16, precision -23, leap 11, trust 000
refid [10.1.1.10], delay 0.02570, dispersion 0.00002
transmitted 4, in filter 4
reference time: 00000000.00000000 Mon, Jan 1 1900 8:05:43.000
originate timestamp: deb22d17.2b1b4cdf Fri, May 25 2018 14:35:03.168
transmit timestamp: deb22cfe.c04d2fb3 Fri, May 25 2018 14:34:38.751
filter delay: 0.02579 0.02597 0.02580 0.02570
  0.00000 0.00000 0.00000 0.00000
filter offset: 24.41716 24.41700 24.41713 24.41714
  0.000000 0.000000 0.000000 0.000000
delay 0.02570, dispersion 0.00002
offset 24.417147

25 May 14:34:38 ntpdate[11180]: no server suitable for synchronization found

把本地加入，然后将 stratum 调整为 8，就可同步。不清楚怎么阿里云的NTP层级这么低都是16了。