NTP (Network Time Protocol) is a University of Delaware, United States (University of Delaware) of David L. Mills made professor in 1985, is used to synchronize the computer time to a communication protocol that allows computers to their servers or clock source (quartz clock, GPS, etc.) to do synchronization, it can provide high-precision time correction (LAN with standard deviation less than 1 ms between, WAN, on dozens of milliseconds), and can be encrypted to prevent the agreement attack.
NTP time server (time server) is to use an NTP server, through which the machine can maintain the network time synchronization. NTP version 1 appeared in June 1988, described in RFC-1059 the first complete NTP norms and related algorithms. This version has been adopted client / server model and the symmetry operation, but it does not support the mandate to identify and NTP control message. Launched in September 1989 to replace RFC-958 and RFC-1059 for NTP v2 version of the RFC-1119.
Almost the same time, the U.S. Digital Equipment Corporation DEC (Digital Equipment Corporation) has launched a time synchronization protocol, the digital time synchronization service DTSS (Digital Time Synchronization Service).
Below to 220.127.116.11 (CAS Time Service Center (Xi'an)) NTP client Example Shao Kai set under way:
Ntpdate command can be synchronized with the time server (if not installed ntp software, CentOS can "yum install-y ntpdate" command to install):
/ Usr / sbin / ntpdate 18.104.22.168 (Chinese Academy of Sciences Time Service Center (Xi'an))
If you want to conduct regular implementation of the ntpdate time synchronization can be carried out by crontab:
Enter the following, the first 15 minutes to an hour to do a time synchronization:
15 * * * * / usr / sbin / ntpdate 22.214.171.124
In addition, there are good and stable server:
(Fudan) (internal users recommended)
Microsoft's timing master (U.S.)
Big Time Service Center, the police station (Taiwan)
Netcom Time Service Center (Beijing)
NTP server (Shanghai)
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