Time synchronization date;hwclock-r

1.

Date displays the system time

Date-s 10:10:10 set system time

When date-s "10:00:00 on 2018-8-8" sets the system time, if you still need to set a date, wrap the date and time values in double quotation marks

Hwclock or clock displays the hardware time. Time in BIOS on motherboard

A command to see the time date;hwclock-r

# hwclock-w writes the system time to the system hardware

Hwclock-s writes the hardware time to the system time:

two.

Stand-alone school time (can only be connected to the Internet)

Available network time servers:

Time.windows.com

Tock.stdtime.gov.tw

Ntp.api.bz

Ntpdate 0.cn.pool.ntp.org

Ntpdate ntp1.aliyun.com

Time synchronization, Linux system needs to install ntpdate

Check whether ntpdate: rpm-qa is installed | grep ntpdate

If not, run the following command: yum install ntpdate

Time synchronization method (server is rarely used):

[root@clent ~] # ntpdate time.windows.com or

[root@clent ~] # / usr/sbin/ntpdate time.windows.com

Crontab scheduling tasks

Time synchronization tasks are executed regularly, so we use crontab-e to add timing tasks

# / 1 * root ntpdatetime.nuri.net;hwclock-w

That is, synchronize the internet time every other hour.

Or

You can see the writing format of scheduled tasks through the vi / etc/crontab command

/ 5 / usr/sbin/ntpdate time.windows.com # synchronize every 5 minutes

Or

/ 5 ntpdate time.windows.com # synchronize every 5 minutes

Crontab-l: lists the contents of the current user's crontab file

Note:

Solve the the NTP socket is in use, exiting problem

[root@esx4 ~] # service ntpd stop

The system time is inconsistent with the hardware time (correct, but the system time is wrong). Hwclock-s writes the hardware time to the system time failure.

Hwclock-w {Save clock} solve the problem!

3. The server uses time to synchronize the server

4. Modify system time profile

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

# Open the clock file and change the relevant content to the following content: UTC=true ARC=falseZONE= "Asia/Shanghai"

Restart the system

[root@localhost ~] # reboot