Chrony has some advantages over old NTPd.

• https://wiki.alpinelinux.org/wiki/Chrony_and_GPSD
• https://forristal.org/blog/2018/01/making-a-raspberry-pi-stratum-1-clock/
• https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html

However, the version packaged for Debian/Ubuntu seems to be broken in that SOCKs don't work. If you manually compile and install it you'll be good.

This assumes a brand new debian-based install.

sudo apt install git bison build-essential asciidoctor -y
git clone https://github.com/mlichvar/chrony
cd chrony
./configure
make ; make docs
sudo make install

A systemd service file is not included, here's a very simple one.

[Unit]
Description=chrony, an NTP client/server
Documentation=man:chronyd(8) man:chronyc(1) man:chrony.conf(5)
Conflicts=openntpd.service ntp.service ntpsec.service
Wants=time-sync.target
Before=time-sync.target
After=network.target

[Service]
Type=forking
ExecStart=/usr/local/sbin/chronyd -f /etc/chrony.conf

[Install]
Alias=chronyd.service
WantedBy=multi-user.target

Install:

cp chronyd.service /lib/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable chronyd

Note! Change ttyAMA0 to whatever your UART is coming in on!

server time-a.nist.gov
server time-a-wwv.nist.gov
server time-a-b.nist.gov

refclock SOCK /run/chrony.ttyAMA0.sock refid GPS

rtcsync

logchange 0.5

local stratum 10

makestep 1.0 3

logdir /var/log/chrony
log statistics tracking

dumpdir /var/log/chrony
driftfile /chrony.drift

allow