[ntp:questions] ntpd -qg VS ntpd in Linux client ?

David L. Mills mills at udel.edu
Sun Apr 29 02:32:11 UTC 2007


Richard,

Small correction. If the time is within the step threshold (128 ms) the 
clock is slewed rather than stepped. This is because the adjtime() 
syscall continues to amortize the offset at the last call. If called 
from a cron job and the intrinsic clock frequency error is relatively 
small, this avoids stepping the clock at each cron job run.

Dave

Richard B. Gilbert wrote:
> Riccardo Castellani wrote:
> 
>> I'm interesting to align time in my four DB servers (HP-UX o.s.) of my 
>> company.
>> But I'm not just sure to use ntpd -qg or ntpd as service.
>> my doubts:
>>
>> -----
>> if I use "ntpd -qg":
> 
> 
> IIRC, ntpd -qg sets (steps) the time unconditionally (-q) and then quits 
> (-g).
> 
>> 1 - if server time is backward real time, does "ntpd -qg" slew time 
>> immediately ?
>> 2 - if server time is forward real time (< 128 ms), does "ntpd -qg" 
>> slew time immediately ?
>> 3  - if server time is forward real time (> 128 ms), does "ntpd -qg" 
>> sleps time ? but Does it complete its job before exit ( also if it 
>> occurs several days ) For example if offset  = 120s, "ntpd -qg" exits 
>> after local time is ok that is after several days ?
>> -----
>>
>>
>> 4- If I have offset = 120s what's difference in using "ntpd" and "ntpd 
>> -qg".
>> 5- what traffic bandwith does ntpd use ?
>> For my opinion "ntpd -qg" is better for client, while ntpd as service 
>> it should be run in time server machines.
>>
>> What do you suggest me ?
> 
> 
> Read and understand the ntpd documentation!
> 
> 
> 
> 




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