• NTP 4.2.8 loses sync, system time far out

    From Matthias Koch@21:1/5 to All on Tue Nov 15 14:16:55 2016
    I am running a number of virtual OpenBSD-Hosts on a VMware-vSphere, with
    the stock ntpd from packages. Their ntpd.confs are pretty straightforward:

    -----
    # $OpenBSD: ntpd.conf,v 1.14 2015/07/15 20:28:37 ajacoutot Exp $
    #
    # See ntpd.conf(5) and /etc/examples/ntpd.conf

    servers pool.ntp.org
    constraints from "https://www.google.com"
    ----- End

    While all machines are syncing properly, one of them (openBSD 6.0) keeps
    losing sync and drifts waaay out. A newstart of ntpd brings the system
    time back on track, but after a few minutes it loses sync again and
    drifts out.

    ntpd ist started with "ntpd_flags='-s -v'".

    Here's a typical output:

    Nov 15 13:57:24 n2 ntpd[9622]: ntp engine ready
    Nov 15 13:57:51 n2 ntpd[94990]: set local clock to Tue Nov 15 13:57:51
    CET 2016 (offset 26.320751s)
    Nov 15 13:57:52 n2 ntpd[9622]: constraint reply from 172.217.16.36:
    offset -0.877704
    Nov 15 13:58:09 n2 ntpd[9622]: peer 52.59.88.68 now valid
    Nov 15 13:58:13 n2 ntpd[9622]: peer 176.9.253.75 now valid
    Nov 15 13:58:15 n2 ntpd[9622]: peer 78.46.189.152 now valid
    Nov 15 13:58:18 n2 ntpd[9622]: peer 87.106.126.46 now valid
    Nov 15 14:02:22 n2 ntpd[39746]: adjusting local clock by 3.956680s
    Nov 15 14:02:22 n2 ntpd[9622]: clock is now synced
    Nov 15 14:02:34 n2 ntpd[9622]: peer 52.59.88.68 now invalid
    Nov 15 14:06:11 n2 ntpd[39746]: adjusting local clock by 3.816125s
    Nov 15 14:06:11 n2 ntpd[9622]: clock is now unsynced

    This is where the first "unsynced" message appears, less than 10 minutes
    after restarting ntpd. From that point on, the clock stays out of sync
    and veers off.

    An almost identical virtual machine, running on the same host, is
    unaffected.

    I'm particularly wondering what's happening here:
    Nov 15 14:06:11 n2 ntpd[9622]: clock is now unsynced

    Any input would greatly be appreciated.

    Matthias

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