When no NTP server is available the device falls back to 1970 for system time.
I believe chrony should be able to pick up system time where it left off if I can get it configured correctly.
https://chrony-project.org/faq.html#_what_if_my_computer_does_not_have_an_rtc_or_backup_battery
5.6. What if my computer does not have an RTC or backup battery?
In this case you can still use the -s option to set the system clock to the last modification time of the drift file, which should correspond to the system time when chronyd was previously stopped. The initial system time will be increasing across reboots and applications started after chronyd will not observe backward steps.
This would not be useful in cases where power may be off for a while. Having system time reset to obviously bad time may be better then a possibly good but incorrect time in some scenarios.
First challenge was getting the -s option set for chronyd. initially I tried /etc/systemd/system/chronyd.service.d/10-add-s-option.conf but I believe with how the read only partition gets mounted, chrony starts, and then this folder was mounted it was not getting there. echo 'OPTIONS="-s"' > /etc/default/chronyd did the trick.
Second challenge was moving default drift file location to something that would survive reboot. in /etc/chrony.conf changed /var/lib/chrony/drift to /overlay/chrony/drift
While there also
makestep 10000 -1
# step any size on any update (useful if GPS/NTP comes later)
After reboot it still goes back to 1/1/1970. Any ideas?
maybe /overlay/ getting put down after chronyd starts?
