CentOS 6
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Chrony : Configure NTP Server
2016/07/28
 
Install Chrony and Configure NTP server for time adjustment.
[1] Install and Configure Chrony.
[root@dlp ~]#
yum -y install chrony
[root@dlp ~]#
vi /etc/chrony.conf
# line 3: change servers for synchronization to your timezone

#
server 0.rhel.pool.ntp.org iburst
#
server 1.rhel.pool.ntp.org iburst
#
server 2.rhel.pool.ntp.org iburst
#
server 3.rhel.pool.ntp.org iburst
server ntp1.jst.mfeed.ad.jp iburst
server ntp2.jst.mfeed.ad.jp iburst
server ntp3.jst.mfeed.ad.jp iburst
# line 25: add the network range you allow to receive requests

allow 10.0.0.0/24
[root@dlp ~]#
/etc/rc.d/init.d/chronyd start

Starting ntpd: [ OK ]
[root@dlp ~]#
chkconfig chronyd on

[2] If Iptables is running, allow NTP port. NTP uses 123/UDP.
For "-I INPUT 5" section below, Replace it to your own environment.
[root@dlp ~]#
iptables -I INPUT 5 -p udp -m state --state NEW -m udp --dport 123 -j ACCEPT

[3] Verify it works normally like follows.
[root@dlp ~]#
chronyc sources

210 Number of sources = 3
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^+ ntp1.jst.mfeed.ad.jp          2   6    37    48  +2180us[+2180us] +/-   80ms
^* ntp2.jst.mfeed.ad.jp          2   6    37    49  +3346us[+2944us] +/-   75ms
^- ntp3.jst.mfeed.ad.jp          2   6    37    48  +3914us[+3914us] +/-  155ms
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