记一次chrony同步失败问题排查

先简单介绍一下chrony

chrony是linux7开始使用的时间同步服务，系统内置。比ntp更加快捷，简单

实际配置中总是出现各种问题，排除时，首先关闭selinux，关闭防火墙。

尝试过多次，最近一次成功的案例是，服务端的配置文件修改了三项

自己是自己的服务器

# Please consider joining the pool (http://www.pool.ntp.org/join.html).
server 192.168.102.11 iburst

开启同步许可
# Allow NTP client access from local network.
allow 192.168.102.0/24

开启同步层

# Serve time even if not synchronized to a time source.
local stratum 10

保存后，本地重启chronyd服务，客户端也重启chronyd服务。可以自动同步

含有服务端和客户端：服务名为 chronyd，客户端工具chronyc

配置文件 /etc/chron.conf

# Use public servers from the pool.ntp.org project.
# Please consider joining the pool (http://www.pool.ntp.org/join.html).
server 192.168.102.131 iburst

此项为时间源地址

修改后需要重启服务，然后用chronyc sources -v 查看同步情况

[root@student ~]# chronyc sources -v
210 Number of sources = 1

  .-- Source mode  '^' = server, '=' = peer, '#' = local clock.
 / .- Source state '*' = current synced, '+' = combined , '-' = not combined,
| /   '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
||                                                 .- xxxx [ yyyy ] +/- zzzz
||      Reachability register (octal) -.           |  xxxx = adjusted offset,
||      Log2(Polling interval) --.      |          |  yyyy = measured offset,
||                                     |          |  zzzz = estimated error.
||                                 |    |          
MS Name/IP address         Stratum Poll Reach LastRx Last sample               
===============================================================================
^? 192.168.102.131               0   8     0     -     +0ns[   +0ns] +/-    0ns

这是服务器不可达，时间未同步的反馈

[root@student ~]# chronyc sources -v
210 Number of sources = 1

  .-- Source mode  '^' = server, '=' = peer, '#' = local clock.
 / .- Source state '*' = current synced, '+' = combined , '-' = not combined,
| /   '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
||                                                 .- xxxx [ yyyy ] +/- zzzz
||      Reachability register (octal) -.           |  xxxx = adjusted offset,
||      Log2(Polling interval) --.      |          |  yyyy = measured offset,
||                                     |          |  zzzz = estimated error.
||                                 |    |          
MS Name/IP address         Stratum Poll Reach LastRx Last sample               
===============================================================================
^* 192.168.102.131               3   6    17    13  +5813ns[ +120us] +/-   41ms

这是正常同步的信息反馈

理论上，只要服务安装了，配置文件没错，重启过服务，关闭了selinux和firewalld，网络通，就会很对进行同步，此次却无法进行同步。

结果发现是客户端的chrony版本比服务端的chrony版本高导致，全部更新到最新版本后马上就同步了