NTP

Installing NTP

yum install ntpd

Configuring NTP

Setting the time zone

Make sure that the host time zone is set properly. To modify the time zone go here

Setting the DNS server

Make sure your nameserver (DNS) is configured correctly (see Modify the dhcp client configuration).

Modify NTP Server List (Optional)

Modify your ntp server list

vim /etc/ntp.conf

Change the server list for those closer to your server. List can be found here
Example for Canadian servers:

server 0.ca.pool.ntp.org
server 1.ca.pool.ntp.org
server 2.ca.pool.ntp.org
server 3.ca.pool.ntp.org

Synchronize the host date with the NTP server

Warning: This may result is a jump in time of several minutes.

Use ntpdate to synchronize your server time with a NTP server.

Example showing a host synchronization with a Canadian server.

ntpdate 0.ca.pool.ntp.org

Start NTP

You can use the following command to enable NTP:

chkconfig ntpd on
service ntpd start
 

Verify NTP server status

To verify the synchronization between the host and the NTP servers:

ntpq -p

Note: After starting the NTP service, the system requires at least 10 minutes to accept a reference server.

Example of host synched with barricade.rack9:

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*barricade.rack9 209.51.161.238   2 u 1001 1024  377   31.147   -0.369  20.074
+ip-72-167-42-82 204.123.2.5      2 u  754 1024  377  166.388  -29.692  28.223
+cheezum.mattnor 129.7.1.66       2 u   91 1024  377   45.715    1.504  47.753

The '*' represent the current reference server
The '+' represent a potential backup reference server
The '-' represent a rejected reference server