[ntp:questions] Unexpected ntpd behavior

David L. Mills mills at udel.edu
Wed Mar 9 04:10:00 UTC 2005

Danny & Co.,

Don't forget to set the kernel frequency to zero when removing the 
frequency file: ntptime -f 0. Otherwise, you are almost guaranteed an 
evil surge.


Danny Mayer wrote:
> 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
>> server
>> 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
>> jitter
>> ============================================================================== 
>> *   4 u   55   64  377    0.308  6418.55
>> 1.565
>>  LOCAL(1)        LOCAL(1)        14 l   21   64  377    0.000    0.000
>> 0.004
>> 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.
> Danny

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