In Linux, the commands used for clock viewing and setting mainly include date, hwclock, and clock. Clock and hwclock are similar in usage, except that clock commands support both x86 hardware systems and Alpha hardware systems.
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. Clock and hwclock are similar in usage, except that clock commands support both x86 and Alpha hardware systems.
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
# Clock -- show
Set hardware Time
# Hwclock -- set -- date = "07/07/06" (month/day/year hour: minute: Second)
# 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.
How does one modify the system time and time zone in Linux:
Modify the time zone:
1>
Find the corresponding time zone file/usr/share/zoneinfo/Asia/Shanghai
Replace the current/etc/localtime file with this file.
Or find the server that you think is the standard time, and then
# Scp root@xxx.xxx.xxx.xxx:/etc/localtime
2>
Modify the/etc/sysconfig/clock file:
ZONE = "Asia/Shanghai"
UTC = false
ARC = false
Modification date and time:
1>
Use date to modify the date and time
# Date-s 08/24/2006
# Date-s 13:02:00
2>
Synchronizes the BIOS clock and forces the system time to be written to CMOS.
# Clock-w
In addition, use # hwclock-r to view Bois time
# Tzselect can be used to interactively modify the time zone
Linux system time zone modification
1. view the current time zone
# Vi/etc/sysconfig/clock
2. modify the time zone
Method (1) # tzselect method (2 Limited to RedHat Linux and CentOS) # timeconfig
3. copy the corresponding time zone file to replace the default time zone of the system.
# Cp/usr/share/zoneinfo/$ Main time zone/$ time zone/etc/localtime: # cp/usr/share/zoneinfo/Asia/Shanghai/etc/localtime
4. write the current time into the BIOS for permanent effect (to prevent failure after restart)
# Hwclock