Linux time settings

I used to set date all the time. This time, I finally got a full set by referring to the online materials.

Linux clock is divided into system clock and real time clock (RTC. The system clock is the current Linux kernel clock, and the hardware clock is the battery-powered clock on the motherboard. This hardware clock can be set in the BIOS. When Linux is started, the hardware clock reads the system clock settings, and then the system clock runs independently of the hardware.

All commands (including functions) in Linux use the system clock settings. In Linux, the commands used for clock viewing and setting mainly include date, hwclock, and clock. Among them, clock and hwclock use similar, just use one line, but clock commands not only support x86 hardware system, but also support alpha hardware system.

1. Date

View system time

# Date

Set system time

# Date -- set "07/07/06" (month/day/year hour: minute: second)

2. hwclock/clock

View hardware time

# Hwclock -- show

Or
# Clock -- show

Set hardware time

# Hwclock -- set -- date = "07/07/06" (month/day/year hour: minute: second)

Or
# Clock -- set -- date = "07/07/06" (month/day/year hour: minute: second)

3. Hardware time and System Time Synchronization

As mentioned earlier, when the system is restarted, the hardware time reads the system time for synchronization. However, if the system time is not restarted, you need to use the hwclock or clock command to synchronize data.

Hardware clock and system clock synchronization:
# Hwclock -- hctosys (HC indicates the hardware time, sys indicates the system time)

Or
# Clock -- hctosys

System clock and hardware clock synchronization:
# Hwclock -- systohc

Or
# Clock -- systohc

4. Time Zone settings

# 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.
#? Input 5, Asia

Please select a country.
1) Afghanistan 18) Israel 35) Palestine
2) Armenia 19) Japan 36) Philippines
3) Azerbaijan 20) Jordan 37) Qatar
4) Bahrain 21) Kazakhstan 38) Russia
5) Bangladesh 22) Korea (North) 39) Saudi Arabia
6) Bhutan 23) Korea (South) 40) Singapore
7) Brunei 24) Kuwait 41) Sri Lanka
8) Cambodia 25) Kyrgyzstan 42) Syria
9) China 26) Laos 43) Taiwan
10) Cyprus 27) Lebanon 44) Tajikistan
11) East Timor 28) Macau 45) Thailand
12) Georgia 29) Malaysia 46) Turkmenistan
13) Hong Kong 30) Mongolia 47) United Arab Emirates
14) India 31) Myanmar (Burma) 48) Uzbekistan
15) Indonesia 32) Nepal 49) Vietnam
16) 33) Oman 50) Yemen
17) Iraq 34) Pakistan
#? Enter 9, China

Please select one of the following time zone regions.
1) East China-Beijing, Guangdong, Shanghai, etc.
2) Heilongjiang
3) Central China-Gansu, Guizhou, Sichuan, Yunnan, etc.
4) Tibet & most of Xinjiang Uyghur
5) Southwest Xinjiang Uyghur
#? Enter 1, Beijing time

The following information has been given:

China
East China-Beijing, Guangdong, Shanghai, etc.

Therefore TZ = 'Asia/Shanghai' will be used.
Local time is now: Fri Jul 7 10:32:18 CST 2006.
Universal Time is now: Fri Jul 7 02:32:18 UTC 2006.
Is the above information OK?
1) Yes
2) No
#? Enter 1, OK

If you do not need the tzselect command, you can modify the time zone of the file.

# Vi/etc/sysconfig/clock
Zone = Asia/Shanghai (query the files under/usr/share/zoneinfo)
UTC = false
Arc = false

# Rm/etc/localtime

# Ln-SF/usr/share/zoneinfo/Asia/Shanghai/etc/localtime

Restart.