what was up with ntp again?

[Brandon Allbery]

On Mon, Mar 23, 2015 at 5:42 AM, René J.V. <rjvbertin at gmail.com> wrote:

> To put it in context: my computers all use the same ntp server (
> fr.ntp.pool.org) so that in theory they share the same clock. Turns out
> that my Mac is about 5min (a bit over 300 seconds) ahead of the others, and
> also of Bradley's VM. I've tried deactivating and reactivating (after
> setting time manually) network time in System Preferences, but it just
> jumps back to the future.
>
> Is this related to the issue that was discussed a while back, and to
> Apple's conflicting service (pacekeeper?)?
> How can I set things right (other than doing a full reinstall of course
> ^^) ?
>

Short version:

    sudo launchctl
unload /System/Library/LaunchDaemons/com.apple.pacemaker.plist
    sudo rm /etc/ntp.drift
    sudo launchctl stop org.ntp.ntpd
    # wait an hour or so for ntpd to establish the current drift
    sudo
launchctl load /System/Library/LaunchDaemons/com.apple.pacemaker.plist

(Which might or might not work; if it doesn't, you'll also need to unload
Apple's ntpd and install some other one --- the MacPorts one works fine ---
for the middle part, then restore Apple's because it has the bits that talk
to pacemaker.)

The longer version I'll briefly gloss: Apple replaced traditional ntp with
one that uses less power and is more laptop friendly, when it works right.
But it assumes that the clock drift of a brand new machine is the same as
that of a fully burned-in and deployed machine, which it might well not be.
The above commands are a "quick reset" of the clock drift, but as Apple
removed some parts of ntp they may not be sufficient to determine the
current clock drift; in that case, you need to use a full ntpd to
characterize the drift, then switch back to Apple's for the improved
performance and power management.

(If your clock still drifts after that, file a radar with Apple. Replacing
Apple's ntpd with a full one is probably not the best of ideas, although it
can be done if needed. But full ntpd is not actually suitable for anything
but certain scientific applications that require nanosecond accuracy; you
pay quite a bit in CPU and power for that accuracy, and there are very few
applications that require more than millisecond clock accuracy. One wonders
how much better Linux etc. would perform if they didn't use full ntpd.)

-- 
brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net
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