[ntp:questions] How to keep fake time in past/future?

Mike Cook michael.cook at sfr.fr
Tue Dec 5 21:02:49 UTC 2017


> Le 5 déc. 2017 à 18:04, William Unruh <unruh at invalid.ca> a écrit :
> 
> On 2017-12-05, romain.cordonnier at gmail.com <romain.cordonnier at gmail.com> wrote:
>> Hi All,
>> 
>> I have the same need as Cristian.
>> 
>> I am working on a data processing project which is designed to run for 25 years.
>> 
>> The customer wants us to run data processing simulation at any time (past/present/future) from 2018 to 2043.
>> 

 If legal time is any essential parameter in the project, there are three major aspects that you will have take into account.
   a) Leap seconds. They are not predictable.
   b) The second NTP epoch will occur in 2036.
   c)The  32bit time_t will roll in 2038.

 The later two will get fixed nearer the dates , but you may not get updated OS/libraries when you need them.

>> Is to possible to build-up a fake "stratum 0" NTP server ?
> 
> Why? Just reset the system clock. Is ntp somehow inextricably embedded in the
> project? ntpd should be setting and disciplining the system clock and all
> software should get their time from the system clock. What is your project
> doing?
> 
> Not that ntp trusts what the server reports. If the server reports that it is
> stratum 1, the clients will believe it. Stratum 0 is not an ntp server. It is
> an outside trusted time source-- atomic clock, gps, .... A server who gets
> time from such a source is a stratum 1 source as I understand it. But if a
> server reports it is stratum 1 it will be believed. 
> 
> 
>> 
>> What are the config options to force the ntp clients to synchronize immediately to the fake source ?
> 
> ntpd does not "sync immediately". If it finds the time out by a sufficient
> amount for a long enough time, it will step the local clock. Or you can
> restart ntpd. 
> 
> 
>> 
>> Steve suggests "Undisciplined Local Clock driver ", any other suggestion ? The time diffusion will be restricted to the project servers (worldwide), it will not be seen by internet.
>> 
>> Thanks in advance !
>> 
>> Romain
> 
> _______________________________________________
> questions mailing list
> questions at lists.ntp.org
> http://lists.ntp.org/listinfo/questions

"The power of accurate observation is commonly called cynicism by those who have not got it. »
George Bernard Shaw



More information about the questions mailing list