Mailinglist Archive: opensuse (1420 mails)

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Re: [opensuse] openSUSE + gpsd + PPS + NTP
  • From: Per Jessen <per@xxxxxxxxxxxx>
  • Date: Wed, 15 Jan 2014 08:32:42 +0100
  • Message-id: <lb5dj6$4ra$2@saturn.local.net>
Roger Oberholtzer wrote:

On Wednesday, January 15, 2014 08:08:29 AM Per Jessen wrote:
Roger Oberholtzer wrote:
On Tuesday, January 14, 2014 11:47:31 AM John Andersen wrote:
NTP will often NOT compensate for several hours of difference.

This is a worry. These systems are in vehicles on the road. We have
no control over the time on the PC clock at boot.

The ntp init script used to run 'ntpdate -g', I'm sure it does
something similar now. That'll set the clock, but with a jump, not a
slow adjustment.

Provided that the GPS is providing times at the time the init script
runs. What if the user turns on the measurement system in a parking
garage where there is no satellite available? Time will not be
available when the init script runs.

Okay.

In typical Catch 22 fashion, the operator cannot know the GPS has
acquired sats and thus be able to provide correct time unless they
turn on the computer. At which time the init script runs. We do not
want the operator to have to assess if the GPS is ready and then run
the init script. Maybe we will need to modify the script so it runs a
program that waits until the GPS has satellites before proceeding? I
suspect that this is the bigger issue than if the BIOS clock is within
one hour of UTC.

Like Cristian suggested, I think this is type of situation that "chrony"
was explicitly written for.

Anyway, assuming that your GPS device is able to notify the system when
it has a stable time signal, it ought not be a big deal to trigger a
set-time command of that event.



--
Per Jessen, Zürich (0.9°C)
http://www.hostsuisse.com/ - dedicated server rental in Switzerland.

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