Install ntp packages
yum install ntp
Redhat 5 need ntpdate separately
yum install nptdate
Set ntp to start on boot:
chkconfig –level 345 ntp on
chkconfig –level 345 ntpdate on
For redhat 7:
systemctl enable ntpd.service
Verify with this:
chkconfig –list | grep ntp
Should show on for boot levels 3,4,5
chkconfig –list | grep ntp
ntpd 0:off 1:off 2:off 3:on 4:on 5:on 6:off
ntpdate 0:off 1:off 2:off 3:on 4:on 5:on 6:off
Edit the config file if you want to use local server
You can change the servers it uses to sync with to be local domain controllers if you don’t have access to the public NTP servers.
The default settings use round robin pools and send you to random servers in the time server pool.
To change edit the Config File /etc/ntp.conf
Change the server lines:
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
Start the service:
systemctl start ntpd.service
or
service ntpd start
Check it is working:
If it is done right you should be able to see the peers actively being used:
ntpq -p
remote refid st t when poll reach delay offset jitter
==============================================================================
+tcgalxdc02.colu 10.1.20.4 3 u – 64 377 0.909 18.481 11.071
*tcghqdc04.colum 128.138.141.172 2 u 7 64 377 25.665 43.190 15.213
If the delay / offset / jitter are zero — it means it is not getting to the server check the firewall is allowing port 123 traffic for ntp through.