✘drift file

Gary E. Miller gem at rellim.com
Tue Aug 2 19:53:09 UTC 2016

Yo Mark!

On Tue, 02 Aug 2016 19:34:16 +0000
Mark Atwood <fallenpegasus at gmail.com> wrote:

> If we make this change, framing it as "it's how chronyd has been
> doing it for the past N years" makes it a much easier sell.

chronyd setting sysclock to driftfile time is only since Agu 2014.  In
Oct 2015 they made it optiona with their -s option, musta been some
problems for some people.  With the non-default -s option it is backward
compatible and people can use it if they want.

A lot of distros, like Gentoo, preceed ntpd with a shell script to 
set a worst case sysclock from a file touched on shutdown.  So the -s is
just internalizing common practice.

Gentoo calls it /etc/init.d/swclock.

> Especially if we can make the file format the same.

ntpd puts just the freq ppm offset on one line in the driftfile.
chronyd puts the freq ppm and the freq skew on one line in the file.

It would be easy to change ntpd to accept the second parameter, and
always write the second parameter.  Then maybe only use the second
parameter with a non-default option.

Only if people like it and gain confidence would it then become 
Best Practice, or even default.

> What principled objections would the hardcore time nerds have?   We
> do have to keep their needs firmly in mind.

I can't see how they can object if the two features are non-default.

Saving the freq skew for restart could improve startup performance,
but how much is TBD.  With the option we can test it.

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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