[ntp:questions] Re: Quasi-On_topic: System (kernel) time jumps 3600 seconds at random times. Stumped.

Brad Knowles brad at stop.mail-abuse.org
Wed May 18 20:00:22 UTC 2005

At 12:46 PM -0700 2005-05-18, elickd at one.net wrote:

>  I'd love to run NTP on every machine we have or at least frequent
>  ntpdates, but our network network group would scream at me if I
>  suddenly started 2500 machines banging away at 4 time servers every 60
>  seconds over frame relay connections(too much jitter already to get the
>  poll times to increase).

	It wouldn't be every sixty seconds, unless you were seriously 
badly misconfigured.  Once started up, a properly behaving NTP client 
should not be contacting the server more frequently than once every 
500-1000 seconds.  And that kind of load should be easily 
sustainable, and can be reduced even further if you were to operate 
in broadcast or manycast mode instead of the typical unicast.

	However, I take your point.

>  So far, running a cron to log time changes is probably my best bet, but
>  it's somewhat daunting because of the extremely random nature of the
>  time errors I'm seeing and the huge quantity of data I'm likely to
>  gather.

	I suspect there's a cron job running somewhere that does 
something like an "rdate" command to a remote server whose clock is 
off, and then there's another cron job somewhere else that does 
something like an "rdate" to another remote time server whose clock 
is reasonably okay.

	That would account for what I recall of the bizarre behaviour you 
are seeing.

Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.

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