setup a Raspberry Pi as an Stratum One NTP server. it is a private project i have made for myself. i did not keeped an eye on network security.

USE IT AT YOUR OWN RISK

Please give me a 'Star', if you find that project useful.

                     ╔═══╗       ╔══════╗         ╔══════╗  GPS-Antenna
                   ──╢ s ║       ║RPi as╟RX───────╢GPS-  ║    ═╪═
                     ║ w ║       ║NTP-  ╟TX───────╢module║     │
                     ║ i ║       ║server║         ╠═══╗  ║     │
       ╔══════╗      ║ t ╟───eth0╢      ╟GPIO#4───╢PPS║  ╟─────┘
       ║ RPi  ╟──────╢ c ║       ║      ║         ╚═══╩══╝
       ╚══════╝   ┌──╢ h ╟──┐    ║      ║
                  │  ╚═══╝  │    ╚══════╝
               ╔══╧══╗   ╔══╧══╗
               ║ PC1 ║   ║ PC2 ║
               ╚═════╝   ╚═════╝

• Raspberry Pi (with LAN)
• SD card
• working network environment (with a connection to internet for installation only)
• GPS module with PPS output (Adafruit Ultimate GPS Breakout - 66 channel w/10 Hz updates - Version 3; https://www.adafruit.com/products/746)

• Raspbian Stretch Lite (2018-11-13, https://www.raspberrypi.org/downloads/raspbian/)

assuming,

• your Raspberry Pi is running Raspbian Stretch Lite (2018-11-13),
• and has a proper connection to the internet via LAN.
• and your SD card is expanded,
• and you connected the GPS module direct to the RPi's RX/TX pins of the GPIO and the GPS PPS pin to the RPi' GPIO #4

1. run bash install-gps-pps.sh to install necessary packages and setup Kernel PPS, GPSD, and NTP with PPS support.
2. reboot your RPi with sudo reboot
3. in case you have a RPi3, RPi3+ or RPi0w with a built-in bluetooth adapter, please run sudo raspi-conf and disable the bluetooth adapter there. otherwise the built-in bluetooth adapter will block the serial port of the GPIO pins.

done.