sntpclock = ntpdate + 22s

[johnea]

Hi,

I recently started running clockspeed 0.62.

Results from ntp servers around the net were consistent for several days, and I thought I had good timekeeping.

Then I noticed that the time displayed at:

http://time.gov/timezone.cgi?Pacific/d/-8/java

was different from my computer's time by > 22 seconds.

I set the computer's time with ntpdate and now I find that the time agrees with time.gov to within a second.

Have I misconfigured clockspeed? Why are ntpdate times and sntpclock times different?

Below are a variety of outputs from sntpclock.

Thank You for any advice!!!

johnea

========================================================================================

[root@cube clockspeed-0.62]# sntpclock 132.239.1.6 | clockview
before: 2007-06-03 11:01:10.388216000000000000
after:  2007-06-03 11:01:10.407884999935477971
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]# sntpclock 198.82.1.201 | clockview
before: 2007-06-03 11:01:21.120580000000000000
after:  2007-06-03 11:01:21.137528742388680577
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]# clockview < /usr/local/clockspeed/etc/atto
before: 2007-06-03 11:01:58.689057000000000000
after:  2007-06-03 11:01:58.689057000586880272
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]# sntpclock 132.239.1.6 > /usr/local/clockspeed/adjust
sntpclock: warning: unable to read clock: timed out
sntpclock: warning: unable to read clock: timed out
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]# clockview < /usr/local/clockspeed/etc/atto
before: 2007-06-03 11:02:21.280021000000000000
after:  2007-06-03 11:02:21.280021000586880292
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]#
[root@cube clockspeed-0.62]# sntpclock 132.239.1.6 | clockview
before: 2007-06-03 11:02:40.344967000000000000
after:  2007-06-03 11:02:40.345191499883428215
[root@cube clockspeed-0.62]# sntpclock 198.82.1.201 | clockview
before: 2007-06-03 11:02:49.789360000000000000
after:  2007-06-03 11:02:49.787162760729104280
[root@cube clockspeed-0.62]#

[Paul Jarc]

johnea <me@...> wrote:
> 22 seconds.

That's the current difference (almost - it's actually 23 now) between
a system clock keeping TAI time (a count of seconds since the
beginning of 1970) and a clock keeping POSIX time (a count of only
non-leap seconds since the beginning of 1970).  A TAI clock increases
smoothly; a POSIX clock jumps back a second when a leap second occurs.
POSIX is more common overall, but clockspeed users tend to use TAI.

Doubts about whether your clock is synchronized usually stem from a
misconfiguration, where you clock is interpreted as TAI by some
programs and as POSIX by other.  To use a TAI clock, you should have
the /etc/leapsecs.dat file installed by clockspeed, and you should use
a right/ time zone (e.g., right/America/Los_Angeles instead of
America/Los_Angeles).  To use a POSIX clock, you should delete
/etc/leapsecs.dat and use a non-right/ time zone.  If you use a POSIX
clock, then when a leap second occurs, you'll have to restart
clockspeed, and either use clockadd to make the one-second jump while
clockspeed isn't running, or let clockspeed bring your clock back into
sync slowly.


paul

[Bennett Todd]

Sounds like you made half the changes necessary.

You've got a choice. You can run your system on TAI, so your system
clock doesn't skip backward for leap seconds; in that case install
/etc/leapsecs.dat from the clockspeed package, and set your TZ to
one of the "right" zones in the zoneinfo database.

Or you can run your system according to the POSIX clock, with the
clock having to reset when there are leap seconds[1], in which case
you can use the normal timezone but need to remove
/etc/leapsecs.dat.

djb has a nice description at
<URL:http://cr.yp.to/proto/utctai.html>

-Bennett

[johnea]

Thank you so much for the helpful replies!

Dang, somehow I overlooked that right/ timezone bit while going through the install.

I downloaded the source and followed the instructions in INSTALL.

The reading at both: http://cr.yp.to/time.html and http://www.thedjbway.org/clockspeed.html
was interesting and illuminating.

Thanks Again for the friendly replies!

johnea