Linux uses NTP service management/synchronization server time_PHP tutorial

Linux uses NTP service to manage/synchronize server time

When there are multiple Web Servers and the time of each server needs to be consistent, then you can consider using NTP service.
1. First use ntpstat to check the current status of the NTP service.
#ntpstat
If the following content is output, it means that it has not started yet. You need to set the NTP service to start automatically when the server is restarted:
Unable to talk to NTP daemon. Is it running?
If the following content is output, it means that it has not started yet. Already working:
synchronised to NTP server (198.55.111.5) at stratum 3
time correct to within 238 ms
polling server every 64 s
If output: unsynchronised, need to restart (ntpd restart) to synchronize.
2. Use ntpq -p to view the NTP server list
#ntpq -p
remote refid st t when poll reach delay offset jitter
============== ================================================== ==============
*dns1.synet.edu. 202.118.1.46 2 u 46 64 377 19.924 11.896 5.692
dns2.synet.edu. 202.118.1.46 2 u 45 64 317 20.518 11.833 6.992
dns.sjtu.edu.cn .STEP. 16 u - 64 0 0.000 0.000 0.000
3. Manual synchronization time
#ntpdate
If the following content is output, it means ntp service It has been started, causing manual time synchronization to fail. You need to stop the ntp service first:
the NTP socket is in use. exiting
#service ntpd stop
#ntpdatecn.pool.ntp.org
If the following content is output , indicating that manual time synchronization is successful:
adjust time server xxx
Finally, remember to start the ntp service and let it update automatically.
4. Start NTP service
#service ntpd start
Starting ntpd: [ OK ]
Enable NTP to start at boot time with the chkconfig command.
5. Enable NTP auto-start
#chkconfig ntpd on
Verify that NTP is enabled with the following command.
6. Check NTP auto-start status
#chkconfig --list ntpd
ntpd 0:off1:off2:on3:on4 :on5:on6:off
Here ntpd is on in runlevels 2, 3, 4, and 5, which is correct.
7. Customized NTP server
Refer here.