Re: [gpsd-dev] Clarifications needed for the time-service HOWTO

[Gary E. Miller]

Yo Eric!

On Tue, 22 Oct 2013 10:08:05 -0400
"Eric S. Raymond" <address@hidden> wrote:

> Gary E. Miller <address@hidden>:
> > > Would you please expand this into a brief discussion of NTP
> > > diagnostic tools for the HOWTO?
> > 
> > The tools we are talking about are for snooping on other peoples
> > chimers.  I would think that is out of scope for this document which
> > whould be focused on how a user makes his own server a goo Stratum
> > 1.
> 
> You told me that for cross-checking purposes one needs to have at
> least two chimers other than the local GPS configured.  I believe
> that, it makes logical sense.

Good, but now I am leaning toward the ntp.pool.org recommendation of
4.

They add them to the ntp.conf file this way:

server 0.pool.ntp.org
server 1.pool.ntp.org
server 2.pool.ntp.org
server 3.pool.ntp.org

They monitor their pool and only use chimers of a certain quality.
From what I can tell they think +/-20 mSec is fine, which is a bit
coarse for our purposes, but a start.  Maybe usefull as a minimmum
acceptable.

> It seems to me that means someone trying to set up a Stratum 1 has
> all the verification issues that anyone setting up an ordinary client
> does.  

I would say we prefer more verification than pool.ntp.org, but they have
been at it a while longer.

> So some guidance to chimer auditing tools seems required.

That hhas been discussed at length on the list.  ntptrace is the
old way, mature but deprecated.  sntp is the new way, nice andd shiny
but moving too fast to document.  ntpq somewhere in the middle.

I like ntpq since it shoow you what your local ntpd is doing relative
to the external chimers you have picked.

Also I like Beat Bolli's idea for scripting the fudge math.  That
should be mentioned (and credited) but I'd put the details in a
script gpsd includes to it just works.

My gut feel is that we are gonna end up writing our own tools.  :-)

> More generally, during the knowledge-capture phase of editing a
> document like this I'm a bit philosophically allergic to
> out-of-scopeness worries. Better to capture too much knowledge and
> then edit for brevity than to err in the opposite direction.

Fair enough.

> I listed you as primary author because a plurality share of the
> content came out of your head.  But I'm the editor; leave the scope
> and structure worries to me, I'll deal with them.  Once the content
> is in good shape I'll do a trimming and polishing pass that may
> cut some stuff.

Fair enough.

> (Harlan, you're getting a pretty good look at how I'd operate if I
> actually took on fixing the ntpd docs...)

Someone IM'ed me this link to another howto last night:

    http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html

Yet another person that thinks this is the way to start gpsd:
         gpsd /dev/ttyACM0 -n -F /var/run/gpsd.sock

And then wonders why it does not work well...

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
        address@hidden  Tel:+1(541)382-8588

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