[ntp:questions] use ntpd, how to know unsync status on linux system

David Woolley david at ex.djwhome.demon.invalid
Mon Aug 16 06:16:20 UTC 2010

赵颖科 wrote:
>         I`m using ntpd(ntp4.2.6p1) as client in linux(2.6.26). I have some questions about my user app how to know the ntp client sync status.
>         1. I use ntp_gettime, is there other way?

That depends on what you want to know about the state of ntpd.  You
probably should want to know the error bound, in which case it is an
appropriate method.  If you really want to know whether it is synched,
you need to use the NTP protocol to either check the stratum (note that
this may take a long time to go to 16, when the last server stops
responding, or more detailed state variables.

>         2. If there is no server alive, when I start ntp client, why ntptime show :ntp_gettime() returns code 0, but not code 5?

I believe there was a policy decision some time ago never to declare a
failure to this interface.

>          I trace the  function loop_config in the file ntpd/ntp_loopfilter.c :
>         I think it should be :
>                 ntv.maxerror = (u_int32)(MAXDISPERSE * 1e6);
>                 ntv.esterror = (u_int32)(MAXDISPERSE * 1e6);

I tend to agree.
>         or not?
>         3. If ntp server no answer for 1h or shortter time, ntpd can mark unsync stat? how could I config ntpd?

Why is this important to you?  The time should still be very accurate at
that point.

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