If I start
$ ntpq -p
promptly, after a reboot, I can see that the system clock is off by up to 600ms.
It takes a while before it converges to the correct NTP time, therefor mildly irritating in our use-case. (Ceph monitors, which are time-sensitive). A following reboot would again show a skewed clock.
Is this to be expected after a reboot, i.e., is the RTC of a PC that inaccurate?
Things I've done to investigate:
- Have seen it on multiple, though very similar, servers (HP dl360 gen9). But also an old white label desktop from 2009.
- Saved a converged NTP time to the RTC, and then copied from the RTC to the system clock. I can only see in the order of 10ms of skew. Perhaps naive, but this basically mimics a reboot as far as the system-time is concerned.
- Explicitly saved to RTC before rebooting; it still occurs
- Used kexec-reboot; it still occurs.
- So far only tested with ubuntu 16.04.