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How can I designate a Mac in my private all Mac network as the Network Time Server and sync up all the clients to the host? The tools I used to use for NTP are now missing in macOS. Are there any NTP Server applications for Mac now? What's replacing NTP in macOS and does it support my private network needs?
ntpd and ntp have been removed by Apple from Mojave. The current tool as used behind the scenes by System Preferences -> Data & Time is now 'sntp' as indicated by MrHoffman.
It is believed Apple did this because NTP has had several security vulnerabilities in the past.
Unfortunately sntp cannot be used as an NTP server only as an NTP client. It will therefore not do what you want.
Your only option would be to install the standard open source ntp software itself and then compile it. Homebrew or similar for Mac might make this easier. It is worth checking to see if you have any other existing servers already capable of acting as an NTP server e.g. Windows or Linux.
While it would be nice to have atomic accuracy all I really need is to keep the clients in closer time with each other than they are now. Connecting to the outside world is not an option (not even GPS) and the network has only Mac clients. In my basic test I've pointed all clients the system I want to them all to sync with and this is working nicely so far. This should keep them all close enough to stop the out of time sync warning. Unless this causes some other problem I'm not aware of at this time?
One issue that arises with drift is certificates and related security, though an entirely isolated network with its own timebase won’t encounter that.
sntp is what Windows has been using for many years.
For those folks were (some) outside connections are an option, GPS receivers with integrated NTP servers are available, including various commercial and lower-budget options.
This assumes GPS reception is legal in the local jurisdiction. Until fairly recently, receiving the EU Galileo GPS system signals was illegal in the United States, for instance.
I did have in the past a network which also had deliberately no Internet connectivity. This meant it was not possible to sync to normal Internet NTP servers. At the time Apple still included NTP software and I was able to configure it to have two Mac servers sync to each other by defining also a third virtual server in the ntp config.
It worked but tended to reinforce the discrepancy between the two servers making them stray from a correct time much faster than a single system. However it achieved the goal of having an active NTP server which clients could sync to. A single NTP server with no feed will not activate itself as an NTP server.
GPS would be possible (at a cost) without Internet access but you would have to trust the GPS signal. Another option would be to use a radio receiver to listen to the radio broadcast of an atomic clock. Again you have to trust the data.
I would not see a radio receiver as a security risk for a standalone network.
In theory this would be fairly cheap - much cheaper than either a real atomic clock or GPS receiver.
See - https://www.vanheusden.com/lpc-ntpd/lindy_precision_clock.php and https://www.lindy.co.uk/usb-precision-clock-corrects-time-on-pcs-p2389
The timed stuff is still around, the ntpdate stuff is getting deprecated upstream, and the command line tool in Mojave is sntp...
Private NTP Server macOS
