Due to hardware reasons, the root standard time of the machine is more or less inconsistent, and the error varies from a few seconds to a few minutes a month. For the server time is not accurate, there will be a lot of trouble. For example, when paying, the order cannot be placed, the game cannot be logged in, etc. It doesn't matter what PC you use, you can just change it manually.
One, use ntpdate to update the time from the time server
If your linux system does not have the ntpdate command at all
yum install ntp
After the installation is complete, you don't need to do any configuration, and you don't need it, just test it directly
[root@localhost ~]# ntpdate time.nist.gov
22 Oct 21:11:43 ntpdate[5014]: adjust time server 207.200.81.113 offset -0.018788 sec
If the above content indicates that the synchronization is successful. Then add the following in crontab.
*/10 * * * * ntpdate time.nist.gov #domain or IP
Sync every ten minutes. Several time servers are recommended.
time.nist.gov
time.nuri.net
0.asia.pool.ntp.org
1.asia.pool.ntp.org
2.asia.pool.ntp.org
3.asia.pool.ntp.org
Second, use ntp to build your own time server
Above, we use other people's time servers to synchronize the time. These time servers are relatively authoritative. When we build our own time server, we don't need crontab to run regularly.
1. Install time server ntp
yum install ntp
2, configure ntp
View Copy Print?
[root@localhost ~]# cat /etc/ntp.conf |awk '{if($0 !~ /^$/ && $0 !~ /^#/) {print $0}}'
restrict default ignore //By default, no modification or query of ntp is allowed, and special packets are not received
restrict 127.0.0.1 //Give all permissions to this machine
restrict 192.168.1.0 mask 255.255.255.0 notrap nomodify //Give the machine on the LAN the permission to synchronize the time
server time.nist.gov prefer //Set the time server, plus prefer means priority
server 0.asia.pool.ntp.org
server 1.asia.pool.ntp.org
server 2.asia.pool.ntp.org
server 127.127.1.0 # local clock
fudge 127.127.1.0 stratum 10
operation file / var / lib / ntp / operation
keys /etc/ntp/keys
3, start ntp
[root@localhost ~]# /etc/init.d/ntpd start
4. Check and test
View Copy Print?
[root@localhost ~]# netstat -upnl |grep ntpd //View the schedule
[root@localhost ~]# ntpq -pn //View the synchronized server IP
remote refid st t when poll reach delay offset jitter
==============================================================================
50.77.217.185 .INIT. 16 u - 64 0 0.000 0.000 0.000
202.90.158.4 .INIT. 16 u - 64 0 0.000 0.000 0.000
202.71.100.89 .INIT. 16 u - 64 0 0.000 0.000 0.000
202.134.1.10 .INIT. 16 u - 64 0 0.000 0.000 0.000
*127.127.1.0 .LOCL. 10 l 18 64 377 0.000 0.000 0.001
[root@localhost ~]# ntpstat //The result of synchronization
synchronised to local net at stratum 11
time correct to within 12 ms
polling server every 512 s
remote: The IP or host name of the NTP host. Pay attention to the leftmost symbol. If it is "+", it means the upper-layer NTP that is currently operating the clock. If it is "*", it means that there is also a connection line, but it is the NTP host that is the secondary connection.
refid: the address of the referenced upper-layer NTP host
st: the stratum class
when: The time synchronization update operation was done a few seconds ago
poll: next update in a few seconds
reach: The number of times the update has been requested to the upper NTP server
delay: the time delay in the network transmission process
offset: the result of time compensation
jitter: Difference time between Linux system time and BIOS hardware time
The first method is recommended. Although it is relatively simple to build a time server, I don't think it is necessary. If you use someone else's time server to synchronize every 10 minutes, it can be accurate to milliseconds.