[CentOS] Date drift and ntpd

[Simon Billis]

Hi,

> > Jason Pyeron sent a missive on 2010-08-12:
> >
> > > We have a local time server and all of our machines are
> > pointed at it
> > > for the time.
> > >
> > > How can the clock drift by a day and a half?
> >
/SNIP
> > It is unlikely that the machine in question drifted forward
> > in time if ntpd was running. Have a look at the logs
> > /var/log/messages it should contain the ntpd log messages
> 
> [root at devserver21 ~]# grep ntpd /var/log/messages
> </snip>
> Jul 28 20:34:41 devserver21 ntpd[3475]: synchronized to 192.168.1.65,
> stratum 3
> Jul 28 21:08:00 devserver21 ntpd[3475]: synchronized to LOCAL(0),
> stratum 10
> Jul 28 21:08:00 devserver21 ntpd[3475]: frequency error -512 PPM
> exceeds
> tolerance 500 PPM

This indicates the hardware clock frequency error exceeds the rate the
kernel can correct. This could be a hardware or a kernel problem.

/SNIP
> Jul 28 23:06:05 devserver21 ntpd[3475]: time reset +0.554019 s
> Jul 28 23:10:14 devserver21 ntpd[3475]: synchronized to LOCAL(0),
> stratum 10
> Jul 28 23:17:36 devserver21 ntpd[3475]: synchronized to 192.168.1.67,
> stratum 3
> Jul 28 23:20:46 devserver21 ntpd[3475]: synchronized to 192.168.1.66,
> stratum 3
> Jul 28 23:22:52 devserver21 ntpd[3475]: synchronized to 192.168.1.65,
> stratum 3
> Jul 28 23:33:28 devserver21 ntpd[3475]: synchronized to 192.168.1.65,
> stratum 3
> Jul 28 23:34:37 devserver21 ntpd[3475]: time reset -0.866445 s
/SNIP
> Jul 29 00:42:44 devserver21 ntpd[3475]: time reset -0.922073 s
/SNIP
> Jul 29 10:50:57 devserver21 ntpd[3475]: time reset -1.638135 s
/SNIP
> Jul 29 15:59:17 devserver21 ntpd[3475]: time reset -1.599691 s
/SNIP

The above lines show that the time on the server was gaining slightly - but
this could be caused by the stratum 3 server losing time slightly due to
loading issues perhaps or by a hardware fault locally


> Aug 12 22:48:29 devserver21 ntpd[3475]: sendto(192.168.1.66): Operation
> not
> permitted

I suspect that you have a firewall in place that is blocking the outgoing
connections from this point.

Rgds

S.