[CentOS] How to set up NTP client (NTP 클라이언트 설정)

NTP(Network Time Protocol)

NTP is network time protocol for maintaining correct system time. It can adjust the time according to a radio or atomic clock and can be tailored to the millisecond time (1/1000 second).

Basically, NTP has a hierarchical structure of stratum.
straum 0       : Equipment for calculating the time. Ex) GPS, CS(cesium) Atomic Clock
straum 1       : Server synchronizing the time from straum 1.
straum 2 ~ n : Time server.

Setup

1. Install packages

1	#> yum -y install ntp

2. Edit configuration file

#> vi /etc/ntp.conf

3. Register NTP service

#> chkconfig ntpd on
#> chkconfig --list | grep ntpd

4. Start NTP service

#> service ntpd start