uc20 rpi not possible to update system time persistently without having internet access

[Bugra Aydogar]

Hi,

While investigating the system-time behavior of UC20 without an RTC, I realized that it is not possible to update the system time persistently. According to the documentation available here => https://ubuntu.com/core/docs/uc20/system-time, systems without RTC gets the time from the mtime of `/var/lib/systemd/timesync/clock`, however if the time is modified by using `timedatectl` or `date` utilities, the system time is updated but the mentioned path's mtime is not updated and thus in the next reboot, system brings up with the kernel-snap's build date.

Repro Steps:
- Create a UC20 image for RPi (you can also disable console-conf)
- Boot it but do not connect to internet
- Create a system-user assertion and login to the system.
- Check the time and update it either with date or timedatectl utiltiy.
- Check the mtime of /var/lib/systemd/timesync/clock, you will realize it is not updated.
- Reboot
- The time is not updated.

Thanks,
Bugra

[Bugra Aydogar (bugraaydogar)]

It seems like this is a known behavior(or issue) within the systemd. I have checked and found it out that the behavior is improved with the commit => https://github.com/systemd/systemd/commit/33e82f3ef33a2497f9838a5fbb924c7501d8dd9e#

This is the original github issue => https://github.com/systemd/systemd/issues/10620

The mentioned fix is available within the systemd version 250. But from the Ubuntu point of view;
Ubuntu Desktop 20.04 and Core20 is using systemd version 245.4-4 and Ubuntu Desktop 22.04 and Core22 will used systemd version 249.11.