Network Time Protocol
Network Time ProtocolÂ (NTP) is a networking protocol forÂ clock synchronization between computer systems overÂ Packet, variable-Latency data networks. Â NTP was originally designed byÂ David L. MillsÂ of theÂ University of Delaware, who still develops and maintains it with a team of volunteers. NTP is intended toÂ synchronizeÂ all participating computers to within a few milliseconds ofÂ Coordinated Universal Time(UTC). It uses a modified version ofÂ Marzullo’s algorithmÂ to select accurate time servers and is designed to mitigate the effects of variable network latency. The protocol is usually described in terms of aÂ client-server model, but can as easily be used inÂ peer-to-peerÂ relationships where both peers consider the other to be a potential time source. Implementations send and receiveÂ time stampsÂ using theÂ User Datagram Protocol(UDP) onÂ port numberÂ 123. As of June 2010, the current protocol is version 4 (NTPv4).
The NTP program is configured using either theÂ /etc/ntp.conf.
NTP or OpenNTPD server software used for configuration.
# yum install ntp
For the one-time synchronization only, use theÂ ntpdateÂ command.
# service ntpd status
# service ntpd stop
# ntpdate â€“b 192.168.0.254
Open the NTP configuration fileÂ
/etc/ntp.confÂ in a text editor such asÂ vim orÂ nano
# vim /etc/ntp.conf
server 192.168.0.254(the hostname or IP address of the site NTP server)
# service ntpd start
# service iptables restart
# netstat â€“tulpn
# chkconfig ntpd on