[ntp:questions] Re: NTP seems unsuitable for this application... what do you think?

Heiko Gerstung heiko.gerstung_removeme_ at meinberg.de
Thu Dec 2 12:56:21 UTC 2004

Hi John,

John Seal wrote:
> We have a networked system with the following characteristics:
> - Not on the internet.
> - Several dozen hosts, mostly Solaris 2.6 and Solaris 9.
> - Normally OFF, turned ON only during use for 8-10 hours at a time.
> - Hosts booted in random order as needed, sometimes not all of them.
> - Clock batteries cannot be easily replaced, so they're often dead.
> - Time (but not date) is available, ultimately from GPS, I think.

If you keep one NTP server running in your network, your hosts could use 
ntpdate or "ntp -g" to aquire the actual time from this NTP server 
during the boot process. Afterwards the ntpd could be started in "normal 
mode" and keeps the system clock of your machines synchronized while 
they are powered up.


> Bottom line: there is a complex boot/login dance using rdate and custom 
> programs that ensures that hosts start out synced to the one special GPS 
> host at the beginning, but then they are free to drift until the system 
> is shutdown.

"ntpdate" would eliminate the need to let your users enter this 
"wristwatch time" and setup the correct date. The system clock would be 
in a state where ntpd could pick up the ball and keeps the time synch'ed 
during the day.


> Our decision, as of this morning, is that NTP really isn't suitable to a 
> system like this that's not ON for long periods of time, not on the 
> internet, has hosts that boot with wildly different local times, and 
> lacks direct connection to a GPS.  What do you think?

Like other vendors we offer dedicated NTP time servers with (for 
example) an integrated GPS reference clock. Check out the LANTIME/GPS on 
our website or look after any other NTP time server from a manufacturer 
you prefer (e.g. Symmetricom, EndRun, ...).

Alternatively you could buy a cheap radio clock and run an old unused PC 
with FreeBSD or Linux as your time server. Or use one of your Sun 
machines (you may just keep one up and running all the time, you can use 
it for other tasks, too), we have a Sun Blade 1000 with Sol9 running 
fine with one of our GPS167 radio clocks.

Bottom Line: No problems for NTP with your setup, all you need is at 
least one good reference and a few lines in the startup scripts of every 


Kind regards,

Meinberg radio clocks: 25 years of accurate time worldwide

Meinberg Radio Clocks

Stand alone ntp time servers and radio clocks based on GPS, DCF77 and 
IRIG. Rackmount and desktop versions and PCI slot cards.

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