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This article shows you how to analyze the time management of the Linux system, the content is concise and easy to understand, it will definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

3.3 system time Management 3.3.1 time Classification

There are two kinds of clocks in Linux, such as hardware clock and system clock.

The hardware clock refers to the clock device on the motherboard, that is, the clock that can usually be set on the BIOS screen.

The system clock refers to the clock in kernel; all Linux-related instructions and functions are set to read the system clock

When Linux starts, the system clock reads the setting of the hardware clock, and then the system clock operates independently

After setting the system time with the date command, the hardware clock will not be modified, so after the system restart, the system time will still read the hardware time, which is why the date setting fails.

3.3.2 hardware modification time

Command: clock/hwclock

Parameters:

-r,-- show reads and prints the hardware clock (read hardware clock and print result)

-s,-- hctosys synchronizes the hardware clock to the system clock (set the system time from the hardware clock)

-w,-- systohc synchronizes the system clock to the hardware clock (set the hardware clock to the current system time)

1. View the hardware clock

[root@pc6 ~] # hwclock-r

Tuesday, May 22, 2018, 10:43:48-0.079097 seconds

Clock is the same as hwclock

[root@pc6] # type-a clock

Clock is / sbin/clock

[root@pc6 ~] # ll / sbin/clock

Lrwxrwxrwx. 1 root root July May 11 2017 / sbin/clock-> hwclock

two。 Synchronize system time to hardware clock

Check the system time, which is on November 2, 2018.

[root@xuegod65 ~] # date

Friday 02 November 2018 22:30:08 CST

View hardware time May 22, 2018

[root@xuegod65 ~] # hwclock

Tuesday, May 22, 2018, 10:56:35-0.921030 seconds

Update the system time to the hardware clock

[root@xuegod65] # hwclock-w

Verify that the hardware clock has been updated successfully

[root@xuegod65 ~] # hwclock

Friday, 02 November 2018 22:36:21-0.458489 seconds

3.3.2 modify system time

Command: date

Parameter: date-help

Modify system time

-s,-- set=STRING sets the time to the time described by the string

[root@xuegod63] # date-s "2018-11-2 22:30"

Friday 02 November 2018 22:30:00 CST

% F full date format, equivalent to% Y-%m-%d

[root@xuegod63 ~] # date "+% F"

2018-11-02

% y year last two digits (00-99)

% Y year

% m month (01.. 12)

% d monthly date (for example: 01)

% M minute (00.59)

% H hours (00-23)

% s seconds (00-60)

[root@xuegod63 ~] # date "+% Y%m%d"

20181102

# you can add the symbols you want before the day of the year

[root@xuegod63 ~] # date "+% Y-%m-%d% H:%M:%S"

2018-11-02 22:34:27

-d,-- date=STRING # displays the time described by a string instead of "current time"

[root@xuegod63 ~] # date-d "+ 1 months" +% F

2018-12-02

Synchronize network time to system time

[root@localhost ~] # ntpdate 210.72.145.44

27 Mar 11:11:24 ntpdate [4766]: adjust time server 210.72.145.44 offset 0.011401 sec

210.72.145.44 (IP domain name of the official time synchronization server of Xi'an time Service Center in China)

After synchronizing the network time to the system time, you can synchronize the system time to the hardware time with hwclock-w.

Modify time zone

It is possible that some systems still fail after restarting after performing the above two steps, so time zone modification is needed.

[root@localhost ~] # tzselect # follow the prompts to select the time zone

[root@localhost ~] # ln-sf / usr/share/zoneinfo/Asia/Shanghai / etc/localtime

Modify system time profile

[root@localhost ~] # / etc/sysconfig/clock

# Open the clock file and change the relevant content to the following

UTC=true

ARC=false

ZONE= "Asia/Shanghai"

Restart the system

[root@localhost ~] # reboot

The above content is how to analyze the time management of Linux system. Have you learned any knowledge or skills? If you want to learn more skills or enrich your knowledge reserve, you are welcome to follow the industry information channel.

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