在我们重新启动 chrony 服务一周之前，我们的集群中已有机器，并且我们检查所有机器上的时间
慢性重启后，所有机器上的时间都正常
2 天后，我们注意到在某些机器上我们的时间差异超过 1 小时
我们看到的是当我们运行 chronyd 服务时，我们从输出中看到：Can't synchronise: no selectable sources
full details
systemctl status chronyd
● chronyd.service - NTP client/server
Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2019-11-01 19:12:36 UTC; 1 day 15h ago
Process: 36664 ExecStartPost=/usr/libexec/chrony-helper update-daemon (code=exited, status=0/SUCCESS)
Process: 36660 ExecStart=/usr/sbin/chronyd $OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 36663 (chronyd)
CGroup: /system.slice/chronyd.service
└─36663 /usr/sbin/chronyd
Nov 02 20:50:01 server_524,sys65.com chronyd[36663]: Forward time jump detected!
Nov 02 20:50:01 server_524,sys65.com chronyd[36663]: Can't synchronise: no selectable sources
Nov 02 20:53:14 server_524,sys65.com chronyd[36663]: Selected source 193.34.2.90
Nov 02 20:53:14 server_524,sys65.com chronyd[36663]: System clock wrong by -6895.552231 seconds, adjustment started
Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.
我们还进行了以下验证，如下所示
但我们没有抓住时间改变的根本原因，有什么建议可能是什么原因吗？
chronyc -n tracking ; date
Reference ID : 193.34.2.90 (193.34.2.90)
Stratum : 7
Ref time (UTC) : Sun Nov 3 09:23:51 2019
System time : 2563.336425781 seconds fast of NTP time
Last offset : +0.000040391 seconds
RMS offset : 0.000760717 seconds
Frequency : 30.168 ppm slow
Residual freq : +0.016 ppm
Skew : 0.907 ppm
Root delay : 0.335443 seconds
Root dispersion : 0.427117 seconds
Update interval : 70.4 seconds
Leap status : Normal
Sun Nov 3 10:07:29 UTC 2019
我们将 hwclock 与机器上的时间进行比较
date ; hwclock
Sun Nov 3 10:40:18 UTC 2019
Sun 03 Nov 2019 10:45:39 AM UTC -0.907261 seconds
chrony的配置是：
more /etc/chrony.conf
# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
server 193.34.2.90 iburst
# Ignore stratum in source selection.
stratumweight 0
# Record the rate at which the system clock gains/losses time.
driftfile /var/lib/chrony/drift
# Enable kernel RTC synchronization.
rtcsync
# In first three updates step the system clock instead of slew
# if the adjustment is larger than 10 seconds.
makestep 10 3
# Allow NTP client access from local network.
#allow 192.168/16
# Listen for commands only on localhost.
bindcmdaddress 127.0.0.1
bindcmdaddress ::1
# Serve time even if not synchronized to any NTP server.
#local stratum 10
keyfile /etc/chrony.keys
# Specify the key used as password for chronyc.
commandkey 1
# Generate command key if missing.
generatecommandkey
# Disable logging of client accesses.
noclientlog
# Send a message to syslog if a clock adjustment is larger than 0.5 seconds.
logchange 0.5
logdir /var/log/chrony
log measurements statistics tracking
更加理智：
1）
chronyc -n sources
210 Number of sources = 1
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^* 193.34.2.90 6 6 377 15 +6522ns[ +94us] +/- 603ms
2）
timedatectl
Local time: Sun 2019-11-03 11:01:13 UTC
Universal time: Sun 2019-11-03 11:01:13 UTC
RTC time: Sun 2019-11-03 11:08:26
Time zone: Etc/UTC (UTC, +0000)
NTP enabled: yes
NTP synchronized: no
RTC in local TZ: yes
DST active: n/a
Warning: The system is configured to read the RTC time in the local time zone.
This mode can not be fully supported. It will create various problems
with time zone changes and daylight saving time adjustments. The RTC
time is never updated, it relies on external facilities to maintain it.
If at all possible, use RTC in UTC by calling
'timedatectl set-local-rtc 0'.
3）
tail -10 measurements.log
2019-11-03 09:20:19 193.34.2.90 N 6 111 111 1111 6 6 0.00 -8.100e-05 1.460e-04 1.477e-06 3.353e-01 4.268e-01
2019-11-03 09:21:30 193.34.2.90 N 6 111 111 1111 6 6 0.00 -7.400e-05 1.660e-04 1.477e-06 3.353e-01 4.279e-01
2019-11-03 09:22:40 193.34.2.90 N 6 111 111 1111 6 6 0.00 -9.400e-05 1.530e-04 1.477e-06 3.353e-01 4.290e-01
2019-11-03 09:23:51 193.34.2.90 N 6 111 111 1111 6 6 0.00 -3.800e-05 1.810e-04 1.478e-06 3.353e-01 4.300e-01
2019-11-03 09:25:01 193.34.2.90 N 6 111 111 1111 6 6 0.00 -1.900e-05 2.210e-04 1.477e-06 3.353e-01 4.311e-01
2019-11-03 09:26:11 193.34.2.90 N 6 111 111 1111 6 6 0.00 -9.500e-05 1.540e-04 1.477e-06 3.353e-01 4.321e-01
2019-11-03 09:27:21 193.34.2.90 N 6 111 111 1111 6 6 0.00 2.880e-04 9.430e-04 1.480e-06 3.353e-01 4.332e-01
2019-11-03 09:28:33 193.34.2.90 N 6 111 111 1111 6 6 0.00 -1.420e-04 1.500e-04 1.477e-06 3.353e-01 4.342e-01
2019-11-03 09:29:43 193.34.2.90 N 6 111 111 1111 6 6 0.00 -9.400e-05 1.340e-04 1.479e-06 3.353e-01 4.353e-01
2019-11-03 09:30:53 193.34.2.90 N 6 111 111 1111 6 6 0.00 -1.330e-04 2.190e-04 1.479e-06 3.353e-01 4.364e-01
4）
# tail -10 statistics.log
2019-11-03 09:25:01 193.34.2.90 5.007e-06 4.996e-06 5.989e-06 3.351e-08 3.524e-07 2.2e-02 5 0 5
2019-11-03 09:26:11 193.34.2.90 2.132e-05 8.896e-05 1.616e-05 4.535e-07 3.464e-06 1.3e+00 6 2 3
2019-11-03 09:27:21 193.34.2.90 4.463e-05 6.743e-06 4.529e-05 3.689e-07 2.964e-06 2.0e-02 5 0 4
2019-11-03 09:28:33 193.34.2.90 5.257e-05 1.377e-04 3.979e-05 9.986e-07 9.823e-06 2.3e-01 6 2 4
2019-11-03 09:29:43 193.34.2.90 4.778e-05 8.748e-05 3.340e-05 1.079e-06 8.638e-06 1.1e-02 5 1 3
==============================================================================================================
Date (UTC) Time IP Address Std dev'n Est offset Offset sd Diff freq Est skew Stress Ns Bs Nr
==============================================================================================================
2019-11-03 09:30:53 193.34.2.90 4.487e-05 1.285e-04 4.349e-05 1.598e-06 1.385e-05 6.8e-02 5 1 4
2019-11-03 09:32:03 193.34.2.90 3.720e-05 8.503e-05 3.075e-05 1.381e-06 2.748e-06 8.3e-03 5 0 5
5）
# tail -10 tracking.log
2019-11-03 09:25:01 193.34.2.90 7 -30.136 0.386 4.996e-06 N 1 5.989e-06 -2.562e+03
2019-11-03 09:26:11 193.34.2.90 7 -30.119 0.581 8.896e-05 N 1 1.616e-05 -2.556e+03
2019-11-03 09:27:21 193.34.2.90 7 -30.081 0.940 6.743e-06 N 1 4.529e-05 -2.550e+03
2019-11-03 09:28:33 193.34.2.90 7 -30.055 1.338 1.377e-04 N 1 3.979e-05 -2.544e+03
2019-11-03 09:29:43 193.34.2.90 7 -29.982 2.099 8.748e-05 N 1 3.340e-05 -2.539e+03
==================================================================================================
Date (UTC) Time IP Address St Freq ppm Skew ppm Offset L Co Offset sd Rem. corr.
==================================================================================================
2019-11-03 09:30:53 193.34.2.90 7 -29.879 3.249 1.285e-04 N 1 4.349e-05 -2.533e+03
2019-11-03 09:32:03 193.34.2.90 7 -28.764 3.389 8.503e-05 N 1 3.075e-05 -2.527e+03
6）
netstat -plaunt | egrep "chronyd"
udp 0 0 127.0.0.1:323 0.0.0.0:* 36663/chronyd
udp6 0 0 ::1:323 :::* 36663/chronyd