Hello all,

Is there anyway to reduce the amount of time ntp takes to set the =
date/time on a computer? I am running a Fedora Core 3 machine with a =
GPS. ntp is setup to accept nmea messages from the GPS and use it to =
set the date/time. The GPS is the only source for the Linux machine (no =
internet). I would like ntp to trust the GPS and set the date/time as =
quickly as possible. I am running ntp 4.2.0a.

Thanks,
Aaron Mitchell
amitchell@eoir.com
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Aaron Mitchell wrote:

>Hello all,
>
>Is there anyway to reduce the amount of time ntp takes to set the date/time on a computer? I am running a Fedora Core 3 machine with a GPS. ntp is setup to accept nmea messages from the GPS and use it to set the date/time. The GPS is the only source for the Linux machine (no internet). I would like ntp to trust the GPS and set the date/time as quickly as possible. I am running ntp 4.2.0a.
>
>Thanks,
>Aaron Mitchell
>amitchell@eoir.com
>_______________________________________________
>questions mailing list
>questions@lists.ntp.isc.org
>https://lists.ntp.isc.org/mailman/listinfo/questions
>
>  
>
How are you starting ntpd now and how long does it take to set the 
time?  What sort of GPS are you using?  Does it have a PPS output and 
are you using it?

Assuming that the GPS receiver has a good signal from at least four 
satellites, I would expect it to take something like eighty seconds to 
get enough data to start synchronizing the clock.

It might be possible for you to use ntpdate (deprecated) to set your 
local clock from the GPS before starting ntpd.  I've never tried it.

You will find that many people here object to the use of ntpdate and 
wish it would go away.  Whatever the potential problems might be, I have 
not personally observed any and routinely use it to unconditionally set 
the clock before starting ntpd.  Ntpdate does lack some of the 
protections built into ntpd and cannot set the clock as accurately or as 
reliably as ntpd can.  If having the time quickly is more important than 
accuracy, go for it.

> Is there anyway to reduce the amount of time ntp takes to set the
> date/time on a computer?

What does your ntp.conf file contain?

> ntp is setup to accept nmea messages from the GPS and use it to set the
> date/time.

Dave Mills made a change a month or two ago to ntp-dev that helps a number
of refclocks to synch "quickly" on initial startup.

I don't remember the exact details or exactly which refclocks were able to
take advantage of this fix.

John Hay is the refclock maintainer for the NMEA clock; perhaps he knows.

H