How to make UTC in a Linux system consistent with CST

Source: Internet
Author: User
Tags cst time local time

First, the basic concept

UTC is the Universal time coordinated abbreviation, which is defined and recommended by the International Radio Advisory Committee and is maintained by the International Time Bureau (BIH) in seconds-based time scales.
UTC is equivalent to the average sun on the Prime meridian (that is, longitude 0 degrees), which was previously expressed in Greenwich Mean Time (GMT).
GMT (Greenwich Mean time) is Greenwich mean when-astronomers use, ITPro to find out.

Coordinated World time (English: Coordinated Universal time, Law: Temps universel coordonné), also known as the world's Unification times, world standard Time, international coordination time. Abbreviations in English (CUT) and French (TUC) are not

With, as a compromise, referred to as UTC.

Beijing time is 8 hours earlier than UTC time, taking January 1, 1999 0000UTC as an example, UTC time is 0 points, Beijing time is January 1, 1999 8 o'clock in the morning the whole. So we were 8 hours apart on time.
At this time the BIOS time and the system time are of course inconsistent, one represents UTC time, and one represents the cst+8 time zone), that is, Shanghai.

In Linux, when viewing time with date:
Tue Sep 15:52:10 CST 2015.

World Coordination Time (Universal times COORDINATED,UTC):
Tue Sep 07:52:10 UTC 2015.

There are two kinds of time difference in GPS system, one is UTC, the other is LT (local time) is different from time zone, UTC is the time of 0 time zone, local time, such as Beijing for eight A.M. (East eight), UTC time Is

0 o'clock, the time is eight hours later than in Beijing, the calculation can be.

According to my personal understanding:
CST should refer to (China Shanghai TIME,CST East Eight time)--Personal understanding
UTC should mean (Universal time COORDINATED,UTC Standard)
Local time is now:tue Sep 15:52:10 CST 2015.
Universal time is now:tue Sep 07:52:10 UTC 2015.
These 2 times should actually be 8 hours apart.

Why? UTC is inconsistent with CST

After the initial installation of the CentOS Linux operating system, the time to click on the system is not consistent with the current time, the difference is 8 hours, although in the installation of the system, we choose the time zone is Shanghai

Zone= "Asia/shanghai", but the default BIOS time for CentOS Linux is UTC time

Second, how to make UTC consistent with CST

Domestic available NTP Server:

ping -t
Pinging [] with 32 bytes of data:
Reply from bytes=32 time=110ms TTL=46
Reply from bytes=32 time=109ms TTL=46
Reply from bytes=32 time=109ms TTL=46
ping -t
Pinging [] with 32 bytes of data:
Reply from bytes=32 time=48ms TTL=51
Reply from bytes=32 time=48ms TTL=51
Reply from bytes=32 time=49ms TTL=51

If you do not have an NTP server installed, you just need to execute the following command first:

Yum Install NTP

Synchronization time using the Ntpdate command is as follows:


Editing the time configuration file
1) #VI / etc / sysconfig / clock edit time profile
Zone= "Asia/shanghai"
UTC = false, hardware clock is not the same as UTC time

# diff /etc/sysconfig/clock  /etc/sysconfig/clock.bak


< UTC=false

< ARC=false


Under Linux, you can also set the current system time zone step by run by running the command Tzselect and then entering the number in front of the option.

[[email protected] home]$ tzselect

Please identify a location so that time zone rules can be set correctly.

Please select a continent or ocean.

 1) Africa

 2) Americas

 3) Antarctica

 4) Arctic Ocean

 5) Asia

 6) Atlantic Ocean

 7) Australia

 8) Europe

 9) Indian Ocean

10) Pacific Ocean

11) none - I want to specify the time zone using the Posix TZ format.

#? 5

2) #ntpdate #Alignment time


16 Sep 09:31:01 ntpdate[22530]: step time server offset 61936.560266 sec

After the above steps, our CentOS Linux system time and computer hardware time are finally CST time, and are all in Shanghai time zone.

3) #hwclock--SYSTOHC #Set hardware time to be consistent with system time and calibrate

After the above steps, our CentOS Linux system time and computer hardware time are finally CST time, and are all in Shanghai time zone.

Small knowledge:

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How to make UTC in a Linux system consistent with CST

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