✘drift file

Gary E. Miller gem at rellim.com
Tue Aug 2 02:40:18 UTC 2016

Yo All!

Eric asked me to write up why I thought the chrony drift file handling
is better than NTPsec's handling.

1.  On startup chronyd checks the time stamp on the drift file.
    if the timestamp > sysclock, the sysclock is set to the timestamp

    This is a nice sanity check on the system clock.

2.  ntpd stores the frequency ppm offset in the driftfile.
    chronyd stores the frequency ppm offset and the 'skew' (estimated accuracy 
    of the existing frequency value).

    Knowing the 'skew' at startup allows chrony to better reject bad
    reclock input.
I can see that saving the 'skew' is a nice touch, but I suspect much the
good chronyd startup behavior is explained elsewhere.

In a related topic, it would be nice (maybe an option) for ntpd to hold
off logging the initial aweful data until after the -g option has
set the system clock.  And a bit longer, so the wonky startup data is

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588
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