The Network Time Protocol (NTP) synchronizes clocks of client computers with a time server. It runs on top of the User Datagram Protocol (udp) and uses port 123.
With Linux, you have a choice. There are 3 different daemon that will implement the NTP Protocol, but ony one of them can be installed and running at a time [2].
There is also a Simplified Network Time Protocol (SNTP). Microsoft Windows OS uses SNTP [7].
You can determine which NTP daemon your system is currently using by checking its status:
sudo systemctl status systemd-timesyncd
or
sudo systemctl status ntp
You can change timesyncd's default time servers in its configuration file at: /etc/systemd/timesyncd.conf.
| Microsoft Windows | time.windows.com |
| Apple | time.apple.com |
For a more comprehensive list of public NTP Servers, see reference [12].
You can check the time, time-zone, and time server with the command:
datetimectl
or even better, the command:
datetimectl show-timesync
or
datetimectl status
You enable synchronization with a time server via the command:
datetimectl set-ntp true
To disable time syncrhronization:
datetimectl set-ntp false
To set the timezone, first get a list of time-zones with the command:
datetimectl list-timezones
The set the time-zone with the command:
datetimectl set-timezone your_Continent/City
You can purchase cheap NTP appliances between $200 - $400.
However, you will probably need 3 of them!
I believe that "Tall Paul Tech" has the right idea. You don't really need, your own GPS based NTP Server. You just need to allow it through your network, and block everything elsei [13]. My problem is that I do not yet know how to make a router out of a Raspberry Pi, and Paul confuses me with his VLANS.
However to see how this would or would not work, I need to set up a Raspberry Pi as a time server. There may also be antennas and receiver for the RPi.
Yes, there are GPS receivers for the Raspberry Pi, and you can do this much cheaper [5].
Make sure that the GPS reciever has an accurate 1 Pulse Per Second (PPS) output. The PPS connects to one of the GPIO pins on the Raspberry Pi or some microcomputer. The best that I can determine from articles on the Internet is that Chroney will that care of processing the PPS, while to get ntpd to process the PPS, you have to complile ntpd from the source.
References:
© Copyright Dr. Ray Franco, PhD, PE | 2006-2024. All rights reserved.
