[chrony-users] chrony configuration help (please)

[Mauro Condarelli <mc5686@xxxxxxxxx>]

*Background:* I have several embedded devices (arm9) running linux (currently: 3.16.1 / Buildroot 2015.5) that are powered up at random intervals (some may be up 24/7, but others may be up only a few hours/week); they may or may not be connected to the Internet (each station is likely to have an intermittent connection). Hardware includes a passable RTC (drifts a few sec/week), while system clock seems much worse (at least one order of magnitude).

*Constraint (IMPORTANT):* System time should be strictly monotonic (i.e.: adjustments may slow the clock but should *never* jump back). This applies also at startup (i.e.: some record must be kept and System Clock should be initialized to the last known time ASAP after boot).

Absolute precision is not a requirement, I can tolerate errors of several seconds, but I cannot leave clocks to drift and rely on manual resynchronization.

My  current /etc/chrony.conf is:
===============================
server 0.it.pool.ntp.org
server 1.it.pool.ntp.org
server 2.pool.ntp.org
server 3.pool.ntp.org

logdir /var/log/chrony
log statistics measurements tracking
driftfile /var/lib/chrony/drift
keyfile /etc/chrony.keys
generatecommandkey
makestep 10 3
maxupdateskew 100.0
dumponexit
dumpdir /var/lib/chrony
rtconutc
rtcautotrim 1
rtcfile /var/lib/chrony/rtc
===============================

This, however, is far from being optimal for (at least) two reasons

1. If, for any reason (e.g.: battery disconnection), the RTC loses the right time Date is severely (several years) in the past for minutes, even if the system is connected to the Internet.
2. In the above event, after several minutes, chrony announces it is going to step by several million seconds (as expected); shortly thereafter system dies... somewhat; i.e.: serial console and ssh are completely unresponsive, but "ping" gets an answer. Nothing is logged.

How should I proceed to debug this?
Any idea?

Thanks in Advance
Mauro

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