[clue] [tech] Asterisk in a virtual machine, timer, timing, & real time clock questions

Jim Ockers ockers at ockers.net
Thu Aug 4 09:33:02 MDT 2011


Hi Collins,

Collins Richey wrote:
> On Mon, Jul 25, 2011 at 4:59 PM, Jim Ockers <ockers at ockers.net> wrote:
>
>   
>> Unfortunately I forgot to stabilize the system clock, and by the end of the
>> day the phones were unusuable because the VM system clock/time was wandering
>> around and even ntpd in the VM refused to work, insisting that it did not
>> know what time it was.
>>     
>
> When the clock is too far out of sync, ntp will refuese to do
> anything. Run ntpdate <clockreferencehost> to force setting the clock,
> then you can start ntp successfully.
>   
Yes, this system (based on CentOS 4.3) was already set to run ntpdate 
against a reliable clock source at boot-up (from rc.local), and ntpd was 
started right after that.  Even so, the clock in the VM was so unstable 
that ntpd could never stabilize the system time.  I think it wandered 
around too much.  In this case ntpd would never reach stratum 3 and 
always insisted that it didn't know for sure what the time was.  After I 
added "clock=pit" to the kernel boot command line then ntpd was able to 
stabilize the system clock.

Jim

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