[ntp:questions] Unexpected ntpd behavior

Danny Mayer mayer at gis.net
Wed Mar 9 01:27:06 UTC 2005

At 06:55 PM 3/8/2005, Pete Buelow wrote:
>Some quick background. Trying to get ntpd running on some IA64 hardware in a
>pretty simple environment. Two machines in a pair relationship, the first
>machine in the pairing talks to a known good NTP server, the other talks to
>it's paired buddy. OS is Debain Sarge stable, ntp is 4.1.0-8. Ntp is
>started with -n -c /path/to/conf -x. Conf is simple, and is below.
>server prefer
>fudge stratum 14 refid LCL
>driftfile /etc/ntp.drift
>pidfile /etc/ntp.pid
>disable stats
>authenticate no
>Problem is, if time is slow compared to (which works just fine,
>it's a timeserver for several hundred lab machines), it will catch up quite
>rapidly (much faster than the 2000s/s rate), and run past. If the time is
>ahead of the server, it will just continue ahead. I found a post below
>which states that it should then turn around eventually, and head the other
>direction, bouncing like a bungee, but I've never run the test that long. I
>have no idea why this behavior is happening. And it is the same behavior on
>both machines.
>A sample ntpq -p output. Clock was set 6 and a half seconds behind
>Node2# ntpq -p
>      remote           refid      st t when poll reach   delay   offset
>*   4 u   55   64  377    0.308  6418.55
>  LOCAL(1)        LOCAL(1)        14 l   21   64  377    0.000    0.000
>Two notes of interest based on other posts I've read
>1. Our tick rate is 1ms instead of 10ms.
>2. On almost all of the test machines, the drift file is populated with the
>value 500. On one it's ~450. According to another poster, that could be the
>source of some issues.
>Thoughts? Ideas? I'm assuming right now that it's either a config or a HW
>issue. I'm running a test now with this config and command line options,
>but am adding "disable kernel" to the config file. Wondering if that will
>change the behavior.
>Thanks in advance if anyone has any help to offer at all.
>Pete Buelow

Dave has just fixed a problem with drift files being pegged at 500. The fix
should be in the latest development build (ntp-dev). You should upgrade
in any case since your version of ntpd is rather old. The quick workaround
is to remove the drift file before start ntpd.


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