Configure NTP server for time adjustment. (RedHat 7.0, CentOS 7.0)

Configure NTP server for time adjustment. (RedHat 7.0, CentOS 7.0) NTP uses 123/UDP.

• update yum

# yum update

• install ntp

# yum -y install ntp

• edit ntp configuration

# vi /etc/ntp.conf

# line 18: add the network range you allow to receive requests
restrict 10.0.0.0 mask 255.255.255.0 nomodify notrap

# change servers for synchronization
#server 0.centos.pool.ntp.org iburst
#server 1.centos.pool.ntp.org iburst
#server 2.centos.pool.ntp.org iburst
#server 3.centos.pool.ntp.org iburst
server 3.kr.pool.ntp.org
server 1.asia.pool.ntp.org
server 0.asia.pool.ntp.org

• start ntpd & enable ntpd

# systemctl start ntpd
# systemctl enable ntpd
ln -s '/usr/lib/systemd/system/ntpd.service' '/etc/systemd/system/multi-user.target.wants/ntpd.service'

• confirm ntpd service

# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
 ==============================================================================
+211.233.84.186  204.123.2.5      2 u   20   64    1    1.895   25.575   0.000
*202-65-114-202. 218.100.41.254   2 u   19   64    1  153.352    9.392   0.000
 7c2956c8.i-revo 245.93.165.128   2 u   18   64    1  223.740   26.403   0.000