Linux server time synchronization

When the Linux server is running for a long time, there will be a certain error in the system time. Generally, you can use the date command to set the time. However, when doing complex operations such as database cluster sharding, there are requirements for the time difference between multiple machines. , then you need to use ntpdate for time synchronization.

Common commands for Linux time operations

date command

Usage:

date [-u] [-d datestr] [-s datestr] [--utc] [--universal] [--date=datestr] [--

set=datestr] [--help] [--version] [+FORMAT] [MMDDhhmm[[CC]YY][.ss]]

1.date: View the current time, the results are as follows:

[root@linuxprobe ~]# date

2016年 04月 29日 星期五 23:04:30 CST

2.date ‘%Y%M%D’ displays the current date according to the format, the results are as follows:

[root@linuxprobe ~]# date "+%Y-%m-%d %H:%M:%S"

2016-04-29 23:30:12

3.date -s “xxx xx:xx:xx” Set system time

[root@linuxprobe ~]# date -s "20160429 15:30:00"


2016年 04月 29日 星期五 15:30:00 CST

The above commands are common operations of Linux system time. For specific commands, see: "This is how you should learn Linux" Chapter 2 Linux commands that novices must master.

Linux time synchronization

Let’s take a look at how we can set up multiple Linux machines in a unified and correct environment in a complex environment: pair-time synchronization
Command: utpdate time server ip
ntpdate -u xx.xx.xx.xx The results are as follows:

[root@linuxprobe ~]# ntpdate -u ntp.api.bz

29 Apr 15:26:27 ntpdate[2667]: step time server 61.153.197.226 offset -311.570389 sec
[root@linuxprobe ~]# date

2016年 04月 29日 星期五 15:26:32 CST

ps：若不加上-u参数， 会出现以下提示：no server suitable for synchronization found
-u：从man ntpdate中可以看出-u参数可以越过防火墙与主机同步；

ntp commonly used servers:

中国国家授时中心：210.72.145.44
NTP服务器(上海) ：ntp.api.bz
美国： time.nist.gov
复旦： ntp.fudan.edu.cn
微软公司授时主机(美国) ：time.windows.com
北京邮电大学 : s1a.time.edu.cn
清华大学 : s1b.time.edu.cn
北京大学 : s1c.time.edu.cn
台警大授时中心(台湾)：asia.pool.ntp.org

Time zone operation

Check time zone:

1.date “%Z”

[root@linuxprobe ~]# date "+%Z"
[root@linuxprobe ~]# CST

2. Use cat /etc/sysconfig/clock to view the current time zone

[root@linuxprobe ~]# cat /etc/sysconfig/clock
# The time zone of the system is 
defined by the contents of /etc/localtime.
# This file is only for evaluation by system-config-date, do not rely on its
# contents elsewhere.
ZONE="Asia/Shanghai"

Set time zone:

Copy the corresponding time zone file and replace the system default time zone file link method
[root@linuxprobe ~]# cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime
[root@linuxprobe ~]

#

ps ：/usr/share/zoneinfo为所有不通地区的时区位置
[root@linuxprobe ~]# ls /usr/share/zoneinfo/Asia/

Aden Bahrain Chungking Harbin Jerusalem Kuala_Lumpur Nicosia Qyzylorda Seoul Thimphu 
Yekaterinburg
……
Almaty Baku Colombo
Baghdad Chongqing Gaza Jayapura Krasnoyarsk Muscat Qatar Samarkand Thimbu Yakutsk

Write system time to hardware (bios)

1.hwclock

[root@linuxprobe ~]# hwclock

2016年04月29日 星期五 15时39分30秒 -0.375972 seconds

2.clock -w

[root@linuxprobe ~]# clock -w

[root@linuxprobe ~]#

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