How to Change NTP Source on XenServer

Summary

This article describes how to change the time source accessed by the Network Time Protocol (NTP) on XenServer 5.

Requirements

XenServer command line interface. Basic Linux CLI knowledge. XenServer 5 console or access to the XenServer CLI via SSH

Background

XenServer 5 ships with a list of Internet NTP servers by default:

0.xenserver.pool.ntp.org
1.xenserver.pool.ntp.org
2.xenserver.pool.ntp.org
3.xenserver.pool.ntp.org
127.127.1.0

Note: The listed servers are for internal testing NTP servers, these time servers are not accessible from the Internet.

Entering an NTP server during installation has been identified as an issue in XenServer 5.0 (Hotfix 1, 2, 3). The issue will be resolved in the next version of XenServer.

Procedure

1. At the XenServer console, select Network and Management Interface. If using SSH to connect to your XenServer or using XenCenter Console (tab), type xsconsole to access the following configuration:

2. Select Network Time (NTP).

3. Type in the password for the root user account.

4. Select Add an NTP Server (Optionally, select Remove All NTP Servers, then proceed to add new NTP servers).

5. Enter the IP address of the NTP server. (Hint: If not currently known, you can use nslookup on the Windows command line to get the IP address of your NTP server.)

6. Once the new time server has been accepted, validate that NTP is running by exiting to the XenServer command line, by selecting Quit in the xsconsole.

7. Verify the Network Time Protocol (NTP) is running on your XenServer, by using service ntpd status.

8. Ensure the new time source is accessible by cycling the network time protocol daemon, using service ntpd restart.

If there are errors, see if the time server is accessible using the ping command. Ping the server and ensure you have network connectivity and TCP port 123 open. If ping fails, there is a networking problem outside the XenServer that must be addressed.

Advanced

To synchronize the hardware clock using the Network Time Protocol daemon, the following file, /etc/sysconfig/ntpd must be edited. Change the following line:
- from -

SYNC_HWCLOCK=no
- to -
SYNC_HWCLOCK=yes