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

[...]

Use Express-Checkout link below to read the full article (PDF).

Buy this article as PDF

Download Article PDF now with Express Checkout
Price $2.95
(incl. VAT)

Buy Linux Magazine

SINGLE ISSUES
Print Issues
Digital Issues
SUBSCRIPTIONS
Print Subscriptions
Digital Subscriptions

Related content

  • Tempus Fugit

    Charly Kühnast, sys admin columnist for 15 years, is searching for lost microseconds.

    more »
  • The sys admin's daily grind: ntpviz

    The Network Time Protocol allows admins to keep time on their computers. Due to the way the system works, this timekeeping is only moderately successful. Charly uses the ntpviz statistics tool to visualize time fluctuation.

    more »
  • Charly's Column – Precise Timekeeping

    After the idea of procuring an atomic clock failed to thrill the other members of Charly's household, our intrepid columnist simply decided to tap into the timekeeping of a GPS satellite. In doing so, he ensured the kind of punctuality at home that only large data centers actually need. Precisely.

    more »
  • Charly's Column

    On vacation we may be happy just to check the position of the sun,but computers need a more accurate measure of time. Luckily, there are atomic clocks that can receive time signals by radio and off the Internet.

    more »
  • Admin Workshop: NTP

    Networks often require very accurate timekeeping. The Network Time Protocol provides the time with precision.

    more »
comments powered by Disqus
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters

Support Our Work

Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.

Learn More

News

Tag Cloud

Administration Community Desktop Events Hardware Linux Mobile Programming Security Software Ubuntu Web Development Windows free software open source