what was up with ntp again?

René J.V. Bertin rjvbertin at gmail.com
Mon Mar 23 07:02:37 PDT 2015

On Monday March 23 2015 09:31:50 Brandon Allbery wrote:

Hi, and thanks!

>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

I don't get point 4: how can ntpd determine anything if it's not running?

>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.

I must say I cannot confirm that I noticed a performance increase when I moved from 10.6 to 10.9 (the contrary on the whole, I'd say), and certainly not one that made me investigate and marvel at how much less CPU ntpd is using ...
Also, I don't care about battery life :)

>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

Was the ntpd shipped with OS X 10.6 a full one? If not, it might be possible to go back to using that one, no?

>applications that require more than millisecond clock accuracy. One wonders
>how much better Linux etc. would perform if they didn't use full ntpd.)

Again I never noticed any such performance issues ... but apparently that's because my Ubuntu hosts don't use ntp but something called ntpdate:
Description: client for setting system time from NTP servers
 NTP, the Network Time Protocol, is used to keep computer clocks accurate by
 synchronizing them over the Internet or a local network, or by following an
 accurate hardware receiver that interprets GPS, DCF-77, NIST or similar time
 ntpdate is a simple NTP client that sets a system's clock to match the time
 obtained by communicating with one or more NTP servers.  It is not sufficient,
 however, for maintaining an accurate clock in the long run.  ntpdate by itself
 is useful for occasionally setting the time on machines that do not have
 full-time network access, such as laptops. 
 If the full NTP daemon from the package "ntp" is installed, then ntpdate is not
Homepage: http://support.ntp.org/

In itself that sounds like something that might be good enough for OS X too. Not that I have that many ways to compare computer clocks to a true reference - I just know that my iPhone gives me essentially the same time as my linux rig.


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