[CentOS] NTP and hardware clock

[John Newbigin]

If you want to use NTP, they you should store GMT in the hardware clock, 
otherwise you might end up with windows style 'my clock is an hour out' 
bugs.  Needless to say, this does not work with a dual-boot 
linux/windows box.

The RH approach of setting the time with ntpdate before starting ntpd is 
IMHO wrong but it does not cause me enough trouble to worry about fixing it.

As for the original problem, ntpd probably relies on DNS to find the 
servers and if it can't find any servers it may fail to start.  This is 
normal daemon behavior, normal for apache anyway.

John.


Grant McChesney wrote:

> On 10/11/06, Dag Wieers <dag at wieers.com> wrote:
> 
>> Hi,
>>
>> I had the following problem today. Because of a misconfigured
>> network switch one system suddenly didn't have any network.
>>
>> After a reboot (with the network still unavailable) NTPD refused to 
>> start.
>> Most likely because the initial ntpdate failed to work. I find this
>> troubling, because when the network was restored, NTPD could have resumed
>> working (like I'd expect from a true daemon).
> 
> 
> I too have similar complaints with NTPD on CentOS 3.  If any of my
> CentOS 3 servers lose power, NTPD refuses to start on next boot.  If I
> check the status on the ntpd process, it says process is dead but pid
> file exists.  Server time changes to hwclock, which is usually off 1
> hour thanks to daylight savings.  Interestingly enough I have never
> had the problem on a CentOS 4 server.
> 
>> Now, what was more peculiar was that the hardware clock was completely
>> off. I also had assumed that somehow the hardware clock was kept in sync,
>> but now after rebooting without network, the system clock was skewed.
>>
>> Is there some way to:
>>
>>  + Make ntpd run, even when no ntp-server could be contacted
>>  + Make ntpd synchronise the hardware clock automatically
>>
>> PS Yes, I know I can run ntpdate from cron or run hwclock to synchronize
>> my hardware clock. But shouldn't this be part of the infrastructure
>> (either ntpd or the initscripts) ?
> 
> 
> That would be a nice feature in the initscript.  I've settled for the
> cron fix for now to keep my hwclock in sync.
> 
> Grant
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> 


-- 
John Newbigin
Computer Systems Officer
Faculty of Information and Communication Technologies
Swinburne University of Technology
Melbourne, Australia
http://www.ict.swin.edu.au/staff/jnewbigin