On Mon, Apr 25, 2011 at 12:47 PM, Denniston, Todd A CIV NAVSURFWARCENDIV Crane <todd.denniston@navy.mil> wrote:


> -----Original Message-----
> From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On
> Behalf Of Mailing List
> Sent: Monday, April 25, 2011 13:57
> To: CentOS mailing list
> Subject: Re: [CentOS] CentOs 5.6 and Time Sync
>
>
>
>      List,
>
>      I was not able to resolve my issue with the time on this machine.
> I
> went ahead and rolled the update back to 5.5 and disabled the update
to
> 5.6.
>
>     What I would like to know is if CentOS 6 might be ok when it rolls
> out, or am I just going to have to keep with 5.5 till EOL?
>
>    Thanks to all with there help.
>

1) I hope you are only talking about having rolled back to the last
working for you kernel from 5.5, not the whole distribution.

2) If I was in your position and had time, my method would be[1]
 a) get the srpm for the last known working kernel (2.6.18-194.32 ???)
 b) get the srpm for the first known not working kernel (2.6.18-238 ???)
 c) expand each of the above srpms into their own rpm build tree
   i.e., rpmdev-setuptree;rpm -i kern1; mv rpmbuild rpmbuild.kern1;
         rpmdev-setuptree;rpm -i kern2; mv rpmbuild rpmbuild.kern2
 d) start looking at the differences in the patches applied in kern1 vs.
those in kern2, i.e., read/diff the kernel.spec files
  see if there were any new ones that seemed likely to be causing the
problem...
  RTFS if necessary to make better guesses.
  Rebuild kernel 2 with patches taken out/modified based on my
investigations and test them and see if I guessed right.
  If no luck, think about opening an TUV bug with lots of the info you
have sent here, they may be interested even if you don't have a
subscription.

[1] Been there, done that:
http://www.gossamer-threads.com/lists/drbd/users/9616


At first I figured this was misconfigured NTP but I actually see this happening on one of my machines as well. Nothing interesting about it in particular but I verified that rolling back to the previous kernel (2.6.18-194.32.1.el5) solves the problem entirely. This happens when NTP is enabled or disabled. I get the following error messages in dmesg which are possibly related.

time.c: can't update CMOS clock from 59 to 0
time.c: can't update CMOS clock from 59 to 0
time.c: can't update CMOS clock from 59 to 0
time.c: can't update CMOS clock from 59 to 0

The time drift is significantly higher than would be expected as normal. Because rolling back the kernel completely solves this issue, this must be a bug.

[root@nexus4 ~]# date; ntpdate -u pool.ntp.org
Mon May  9 16:51:03 PDT 2011
 9 May 16:50:21 ntpdate[22117]: step time server 207.182.243.123 offset -42.418572 sec

[root@nexus4 ~]# date; ntpdate -u pool.ntp.org
Mon May  9 16:50:33 PDT 2011
 9 May 16:50:35 ntpdate[22127]: step time server 207.182.243.123 offset -0.692146 sec

Brandon