NTPD Installation

NTPD is the daemon service for NTP server.

Step 1

yum install ntp
chkconfig ntpd on

Install ntp RPM via yum.

Step 2

vi /etc/ntpd.conf

restrict 192.168.0.0 nask 255.255.0.0

server stdtime.gov.hk prefer
#server 0.centos.pool.ntp.org
#server 1.centos.pool.ntp.org
#server 2.centos.pool.ntp.org

To edit ntp.conf basic setting

vi /etc/sysconfig/ntpd

OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid"
SYNC_HWCLOCK=yes

To edit /etc/sysconfig/ntpd basic setting

Step 3

/etc/init.d/ntpd start netstat -tlunp Proto Recv-Q Send-Q Local Address Foreign Address PID/Program name udp 0 0 192.168.1.254:123 0.0.0.0:* 15118/ntpd udp 0 0 127.0.0.1:123 0.0.0.0:* 15118/ntpd udp 0 0 0.0.0.0:123 0.0.0.0:* 15118/ntpd udp 0 0 :::123 :::* 15118/ntpd

Start ntpd and check in UDP listen port 123 for ntpd

Step 4

[root@linux ~]# ntpstat

synchronised to NTP server (220.130.158.71) at stratum 3
   time correct to within 495 ms
   polling server every 64 s


[root@linux ~]# ntptrace -n 127.0.0.1
127.0.0.1: stratum 3, offset -0.034965, synch distance 0.109233
220.130.158.71: stratum 2, offset -0.000873, synch distance 0.031625
220.130.158.50: timed out, nothing received
***Request timed out


[root@linux ~]# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*220-130-158-71. 220.130.158.50   2 u   53   64   77   36.800  -10.496   1.890
 220-130-158-51. .INIT.          16 u    -   64    0    0.000    0.000 4000.00
+220-130-158-51. 220.130.158.50   2 u   49   64   77   33.448  -10.431   2.581
 LOCAL(0)        LOCAL(0)        10 l   51   64   77    0.000    0.000   0.004

Use ntpstat , ntptrace and ntpq to check the NTP connection between you server and upper NTP server.

Step 5 - Client side

ntpdate serverip

In client ntp server, try update maually first. if success update then add to cronjob.

crontab -e

0 0 * * * /usr/sbin/ntpdate serverip &> /dev/null