NTP XNTPD SECONDARY SOURCE

[Andrew Luis Arruza]

I want to have a secondary source for ntp in case my primary source is down.
Is there a way to include a secondary source in the /etc/ntp.conf file?
For example my xntp server is called timewarp and I want to make time.nist.gov as the secondary source.
Any/all help greatly appreciated and points will be assigned.
Thanks,
Andy

[Bill Hassell · Accepted solution]

Actually, you want 4 to 6 different time servers. NTP is a very robust protocol that works best when there are several sources. Through a complex set of measurements and internal tests, NTP will pick the most accurate source and ignore sources that do not respond or are many minutes out of sync. Here is a suggested ntp.conf file:

server ntp-cup.external.hp.com # HP open time server
server time.twc.weather.com # The Weather Channel, Atlanta
server bonehed.lcs.mit.edu # MIT, Boston
driftfile /etc/ntp.drift

For a list of other servers, go to ntp.org, or specifically, http://www.eecis.udel.edu/~mills/ntp/servers.html

Note that Stratum level one servers should only be used once at a particular site as these are the closest to the atomic clock source. Stratum 2 servers have less restrictions but due to NTP's method of resolving time, no less accurate. You'll get better than 128ms accuracy. Your HP-UX system is automnatically a timeserver with the above ntp.conf file (you can chooes other time sources) and other HP-UX and Windows boxes can sync off your server. The protocol is very tiny...you can sync thousands of systems with a small HP-UX system.

There is no need to pick a primary and secondary although the prefer option can lean towards that server. It's much better to let NTP evaluate all the sources and adjust time accordingly.