CentOS System setup time, time zone, settings, and time synchronization

One, time zone

1, view or modify the system time method is as follows:

The code is as follows	Copy Code
#date View System time #date-S modification time, see the following example #date-S 05/16/2010 (set the system date to May 16, 2010) #date-S 12:40:22 (set system time to 12:40:22)

Execution after modification: clock-w, forcing time to be written to COMs

2. Modify the time zone method: (Write the asia/shanghai-Shanghai time zone to the current time zone)

The code is as follows	Copy Code
Cp-f/usr/share/zoneinfo/asia/shanghai/etc/localtime

Tip Whether to overwrite, enter Y return, and then
Date
View time zone and time (CST, China time zone)

3, set the time synchronization method (the following to run as root user)

Use Ntpdate calibration time, not installed, first install NTP

The code is as follows

Copy Code

Yum Install Ntp-y Use Windows Server to synchronize standard time Ntpdate time.windows.com The ntpdate time.windows.com can be added to the crontab to synchronize regularly. Transport crontab: Crontab–e Found: -bash:crontab:command not found Minimized version is not with crontab Install Crontab: Yum Install Cronie-y To see if the installation was successful: Crontab-l No crontab for root indicates successful installation Set to boot up: Chkconfig--level 2345 Crond on Start crontab: Service Crond Start Set automatic sync every 23:59 Crontab-e * * * * ntpdate time.windows.com

Modify Time Zone

The code is as follows	Copy Code
Cp/usr/share/zoneinfo/asia/shanghai/etc/localtime

Time zone information exists under/usr/share/zoneinfo/, the local time zone information exists/etc/localtime, using the tab skill, you can modify the time zone arbitrarily
Tzselect, interactive command, but it seems not too good, or use the above bar.

Second, time

Concept: Linux time has two

System time: Also called software time (SYS), the number of seconds from January 1, 1970 to the current time
Bois time: Also called hardware time (HC)

Show time

[Root@localhost ~]# Date;hwclock-r
Friday, October 19, 2012 23:39:44 CST
October 19, 2012 Friday 23:39 45 sec -0.317993 seconds

Set time

1, Date-s
Date-s 20121019

Date-s 23:40:00

You can use this if you don't have a network.

2, Ntpdate

Do not install ntpdate can yum:

Yum Install-y ntpdate

Join Scheduled Tasks and sync clocks every 10 minutes

Crontab-e
0-59/10 * * * */usr/sbin/ntpdate time.windows.com | Logger-t NTP

In this way, we can solve the problem of inaccurate time in the CentOS system.

Date-s//Set the current time, only root permission to set, others can only view.
Date-s 20061010//set to 20061010, this will set the specific time to empty 00:00:00
Date-s 12:23:23//Set specific time, do not make changes to date
Date-s "12:12:23 2006-10-10″//so you can set all the time