一、描述

CentOS 7 配置ntp时，在ntp.conf中配置server 10.10.192.1 iburst与server 10.10.192.3 iburst,同时执行systemctl start ntpd启动对时服务，但是在第二天执行date查看时，服务器时钟仍然存在一天的误差，ntp对时居然无效。

[root@localhost ~]# date
2023-01-30 01:02:25
#实际时间是2023-01-31才对
#此处date显示的内容是因为执行过alias date="date '+%Y-%m-%d %H:%M:%S'"

二、排查过程：时区显示的问题

1. 从ntp配置方面排查了多次没有发现问题。

2. 查看/var/log/message中ntp日志，发现具有对时操作,ntp服务正常

Jan 30 01:02:11 localhost ntpd[10398]: 0.0.0.0 c012 02 freq_set kernel 0.000 PPM
Jan 30 01:02:11 localhost ntpd[10398]: 0.0.0.0 c011 01 freq_not_set
Jan 30 01:02:19 localhost ntpd[10398]: 0.0.0.0 c61c 0c clock_step +0.947240 s
Jan 30 01:02:19 localhost ntpd[10398]: 0.0.0.0 c614 04 freq_mode
Jan 30 01:02:20 localhost ntpd[10398]: 0.0.0.0 c618 08 no_sys_peer
Jan 30 01:17:41 localhost ntpd[10398]: 0.0.0.0 c612 02 freq_set kernel 2.066 PPM
Jan 30 01:17:41 localhost ntpd[10398]: 0.0.0.0 c615 05 clock_sync

3. 执行ntpstat查看状态,由于长时间对时，当前对时周期为1024秒

[root@localhost ~]# ntpstat 
unsynchronised
   polling server every 1024 s

4. 百思不得其解之时，上网寻求帮助，看到一篇文章提示，要注意时区是否一致。随后使用原始的date命令查看：

[root@localhost ~]# unalias date
[root@localhost ~]# date
Mon Jan 30 20:19:46 EST 2023

注意到上面的时区是”EST“，这是Eastern Standard Time东部标准时间，主要用于北美。我国用的时间是中国标准时间CST(China Standard Time)

三、问题解决：修改时间时区

查看当前系统设置的时区

ba[root@localhost ~]# ll /etc/localtime 
lrwxrwxrwx. 1 root root 38 2021-08-25 04:51:23 /etc/localtime -> ../usr/share/zoneinfo/America/New_York
[root@localhost ~]# echo $TZ

[root@localhost ~]# timedatectl 
      Local time: Mon 2023-01-30 20:33:31 EST
  Universal time: Tue 2023-01-31 01:33:31 UTC
        RTC time: Tue 2023-01-31 01:33:31
       Time zone: America/New_York (EST, -0500)
     NTP enabled: yes
NTP synchronized: yes
 RTC in local TZ: no
      DST active: no
 Last DST change: DST ended at
                  Sun 2022-11-06 01:59:59 EDT
                  Sun 2022-11-06 01:00:00 EST
 Next DST change: DST begins (the clock jumps one hour forward) at
                  Sun 2023-03-12 01:59:59 EST
                  Sun 2023-03-12 03:00:00 EDT
[root@localhost ~]# date -R
Mon, 30 Jan 2023 20:34:03 -0500
#可以通过timedatectl list-timezones查看系统当前支持的时区

设置时区

1. 声明变量，该方法仅是修改当前会话的时区，在重新登录时失效

[root@eas-heq61-12-12-46 ~]# export TZ="Asia/Shanghai"
[root@eas-heq61-12-12-46 ~]# date
Tue Jan 31 09:30:46 CST 2023

2. 使用命令：timedatectl ,永久有效

[root@localhost ~]# date
Mon Jan 30 20:36:53 EST 2023
[root@localhost ~]# timedatectl 
      Local time: Mon 2023-01-30 20:38:21 EST
  Universal time: Tue 2023-01-31 01:38:21 UTC
        RTC time: Tue 2023-01-31 01:38:21
       Time zone: America/New_York (EST, -0500)
     NTP enabled: yes
NTP synchronized: yes
 RTC in local TZ: no
      DST active: no
 Last DST change: DST ended at
                  Sun 2022-11-06 01:59:59 EDT
                  Sun 2022-11-06 01:00:00 EST
 Next DST change: DST begins (the clock jumps one hour forward) at
                  Sun 2023-03-12 01:59:59 EST
                  Sun 2023-03-12 03:00:00 EDT
[root@localhost ~]# timedatectl set-timezone Asia/Shanghai
[root@localhost ~]# date
Tue Jan 31 09:38:39 CST 2023
[root@localhost ~]# timedatectl 
      Local time: Tue 2023-01-31 09:38:47 CST
  Universal time: Tue 2023-01-31 01:38:47 UTC
        RTC time: Tue 2023-01-31 01:38:47
       Time zone: Asia/Shanghai (CST, +0800)
     NTP enabled: yes
NTP synchronized: yes
 RTC in local TZ: no
      DST active: n/a
[root@localhost ~]# ll /etc/localtime 
lrwxrwxrwx 1 root root 35 Jan 31 09:38 /etc/localtime -> ../usr/share/zoneinfo/Asia/Shanghai