Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over Packet, variable-Latency data networks. NTP was originally designed by David L. Mills of the University of Delaware, who still develops and maintains it with a team of volunteers.
NTP is intended to synchronize all participating computers to within a few milliseconds of Coordinated Universal Time(UTC). It uses a modified version of Marzullo’s algorithm to select accurate time servers and is designed to mitigate the effects of variable network latency.
The protocol is usually described in terms of a client-server model, but can as easily be used in peer-to-peer relationships where both peers consider the other to be a potential time source.
Implementations send and receive time stamps using the User Datagram Protocol(UDP) on port number 123. As of June 2010, the current protocol is version 4 (NTPv4).
The NTP program is configured using either the /etc/ntp.conf.
NTP or Open NTPD server software used for configuration.
# yum -y install ntp
For the one-time synchronization only, use the ntpdate command.
# systemctl status ntpd
# systemctl stop ntpd
# ntpdate -b 192.168.0.254
Open the NTP configuration file /etc/ntp.conf in a text editor such as vim or nano
# vim /etc/ntp.conf
server classrrom.example.com(the hostname or IP address of the site NTP server)
# systemctl start ntpd
# systemctl restart firewalld
# systemctl enable ntpd