The sys admin's daily grind: Ntpd

Borrowed Time

Article from Issue 154/2013
Author(s):

The Network Time Protocol keeps Charly up to date at all times. To put all of this punctuality in the service of the common good, he even exports the time signal.

If the clock on my personal laptop is a few seconds fast or slow, this is not dramatic. On a server, however, it's different. Logfiles should  – at least – be synchronized to the exact second; otherwise, troubleshooting becomes a pain. The software that handles this synchronization is, of course, the NTP daemon (ntpd) [1]. As a special hardware time source, you could use a suitable DCF  77 or GPS receiver, for example. If you don't have one of those, you could ask some other time servers – you need to poll several to compute the time from the running time differences of the UDP packets on the network.

The NTP configuration in the /etc/ntp.conf file on my Ubuntu lab machine lists five time servers:

server ntps1-0.cs.tu-berlin.de iburst
server ptbtime1.ptb.de iburst
server ntp1.fau.de iburst
server ntp.probe-networks.de iburst
# Use Ubuntu's ntp server as a fallback.
server ntp.ubuntu.com

[...]

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