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Re: openntpd and ntpq



Ben Goren (ben_(_at_)_trumpetpower_(_dot_)_com) wrote:

> Is there a good way to monitor ntpd? I find nothing in the manual pages
> nor on openntpd.org.

What I've done is set it up to run under daemontools [1], with the "-d"
(don't daemonize; log to stderr) flag.  Then I can use "tail -f" (or on
GNU/Linux, "tail --follow=name" which does the same thing as OpenBSD's
"tail -f") on daemontools's "current" log to see how it's behaving itself.

On the OpenBSD box, it's been behaving itself quite well, so long as
I don't run a recent Freenet node.  (With a recent Freenet node running,
my NTP packets seem to get delayed coming back in, and then I start
seeing delays of 5-6 seconds in the ntpd logfile.  The sync measurements
to the upstream server get all wacky, and the clock starts diverging
pretty badly, as it gets set forward or back almost a full second at a
time.)

On one of my Linux boxes, the clock managed to get itself out of sync
by an ever-increasing amount, and the adjtime() calls didn't seem to
have any effect.  When it was about 16 seconds slow (took about a week),
I finally got sick of it, stopped ntpd, slammed the clock forward with
ntpdate, then restarted ntpd.  Since then, it's stayed within 1 second
of the OpenBSD box.  (But I haven't stressed it much lately...  I've kept
my Freenet node mostly off for the last week.)

I haven't yet determined whether adjtime() on Linux is completely broken,
or whether it just can't handle too-large values and silently ignores
the requests to speed the clock up.  To be fair, I also installed the
"adjtimex" package on the Linux box some time during that mess, but I
haven't yet invested the time in trying to figure out how it works....

[1] http://cr.yp.to/daemontools.html

--
Greg Wooledge                  |   "Truth belongs to everybody."
greg_(_at_)_wooledge_(_dot_)_org              |    - The Red Hot Chili Peppers
http://wooledge.org/~greg/     |

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