[ntp:questions] Clock suddenly running ahead overnight, sometimes.

David Lord snews at lordynet.org
Mon Aug 20 20:21:07 UTC 2012


geep wrote:
> Hope this post isn't too off-topic for ntp forum...
> Haven't used my Slackware Linux PC for a couple of days. When started 
> this morning was surprised to see:
>  20 Aug 09:10:49 ntpdate[3116]: step time server 139.143.5.30
>   offset -684197.258181 sec                    
> whilst running:
>   timeserver1="ntp1.npl.co.uk"
>   timeserver2="ntp2.npl.co.uk"
>   /usr/sbin/ntpdate -b  $timeserver1 $timeserver2
> from /etc/rc.d/rc.local
> 
> Looking in /var/syslog (see below) I can see three occasions recently 
> when the clock has raced ahead whilst the PC is switched off.
> 
> I'm about to go and buy a new CMOS battery. Battery is 5 years old, same 
> as the PC. But intuitively I'd have thought that an old battery would make
> the clock run slow.
> 
> Curious to know if others have seen fast clocks with old batteries?
> Or any other observations...

Depends on the crystal cut and tempco so can be either
direction or if you are very, very lucky a low tempco for
temperature variations at your site.

If you are are either multibooting or the pc is not running
24/7 then you are probably expecting too much of ntpd. With
a stable drift files my pcs can mostly be in sync within an
hour after a reboot but a new system might take a few days
to a stable offset of < 1ms (after that the drift file will
be reliable).


David

> Keeping my fingers crossed that a new battery will fix the fast clock.
> And maybe a recent rebooot problem, which only affects the OS on one of my
> disk drives. The PC will only reboot properly when 'cold' e.g. overnight 
> switch-off, but this only affects the OS (Linux & Win7) on 1 particular
> disk. Rebooting during the first 5 minutes is fine, but after that it 
> just reboots to the legacy grub menu. All other disks/OS reboot OK.
> 
> Cheers,
> Peter
> 
> grep "Dquot-cache hash table" syslog | awk '{print $1,$2,$3}' | tail -n 20
> Aug 6 09:04:34
> Aug 6 17:16:41
> Aug 7 09:50:31
> Aug 8 18:25:25
> Aug 8 22:02:14
> Aug 9 16:18:41
> Aug 10 18:41:47
> Aug 11 08:33:38
> Aug 17 12:18:24
> Aug 13 17:21:06
> Aug 14 08:11:51
> Aug 14 18:23:30
> Aug 14 20:38:13
> Aug 15 16:59:58
> Aug 21 02:16:06
> Aug 17 22:02:15
> Aug 16 20:42:10
> Aug 19 13:57:42
> Sep 4 18:38:03
> Aug 28 07:09:02
> 



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