十單元補充：時間同步

#####4.如何同步系統時間######

1.服務端
yum install chrony -y   ##安裝服務
vim /etc/chrony.conf       ##主配置文件
 22 # Allow NTP client access from local network.
 23 allow 192.168/16    ##允許誰去同步我的時間

 29 # Serve time even if not synchronized to any NTP server.
 30 local stratum 10    ##不去同步任何人的時間，時間同步服務器級別

system restart chronyd
systemctl stop firewalld

2.客戶端
vim /etc/chrony.conf
  3 #server 0.rhel.pool.ntp.org iburst
  4 #server 1.rhel.pool.ntp.org iburst====>server ntpserverip iburst
  5 #server 2.rhel.pool.ntp.org iburst====>
  6 #server 3.rhel.pool.ntp.org iburst

systemctl restart chronyd

測試：
[root@foundation50 ~]# 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
||                                                /   xxxx = adjusted offset,
||         Log2(Polling interval) -.             |    yyyy = measured offset,
||                                  \            |    zzzz = estimated error.
||                                   |           |                         
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^? bogon                         0  10     0   10y     +0ns[   +0ns] +/-    0ns

###5.timedatectl命令###
timedatectl              status             ##顯示當前時間信息
                            set-time HH：mm：ss ##設定當前時間
                         set-timezone       ##設定當前時區
                         set-local-rtc 0|1  ##設定是否使用utc時間