And the Time Is …

Charly's Column – ntpviz

Article from Issue 228/2019
Author(s):

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.

I recently browsed the NTPsec repository [1], a heavily reworked fork of the well-known Network Time Protocol daemon, ntpd. The newcomer is looking to ditch legacy ballast and finally provide protection against Man-in-the-Middle attacks. NTPsec is not the topic today, but I would like to talk about a small tool that I found while browsing: ntpviz. Among other things, the program visualizes the extent to which the time queried by the NTP server deviates from the local time (offset) and how strongly it fluctuates (jitter).

To get started, I cloned the Github repository and started the installation:

cd /usr/local
git clone --depth 1 https://gitlab.com/NTPsec/ntpsec.git
cd ntpsec
./buildprep
./waf configure --refclock=all && ./waf build && ./waf install

Then I created the directory where the statistics data will be stored:

mkdir /var/log/ntpstats

What's missing is /etc/ntp.conf from Listing 1. Now I can start the NTP daemon. With the parameter -N it runs with increased priority – this improves the accuracy:

ntpd -c /etc/ntp.conf -N

Listing 1

/etc/ntp.conf

 

Now, I have a day off – after all, ntpd has to collect enough statistics. Typing

ntpviz @day/optionfile

was supposed to start the visualization, but it blew up in my face the first time I tried it. It turns out that Gnuplot has to be installed – a fact that slipped by me when checking the dependencies. After installing Gnuplot everything runs like clockwork: The www/day subdirectory contains an HTML file with various graphs (Figure 1).

Figure 1: Jitter statistics of four NTP servers queried over a period of 12 hours.

The Author

Charly Kühnast manages Unix systems in the data center in the Lower Rhine region of Germany. His responsibilities include ensuring the security and availability of firewalls and the DMZ.

Buy this article as PDF

Express-Checkout as PDF
Price $2.95
(incl. VAT)

Buy Linux Magazine

SINGLE ISSUES
 
SUBSCRIPTIONS
 
TABLET & SMARTPHONE APPS
Get it on Google Play

US / Canada

Get it on Google Play

UK / Australia

Related content

  • Tempus Fugit

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

  • Charly's Column: Ntpd

    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.

  • 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.

  • NTPsec: The Wrong Fork for the Wrong Reasons
  • Charly's Column

    Using SQL to sift syslog data out of a database is an admittedly universal, but also fairly convoluted approach. phpLogCon, with its web interface, gives admins an easier option.

comments powered by Disqus

Direct Download

Read full article as PDF:

Price $2.95

News