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

William Unruh unruh at invalid.ca
Tue Dec 5 17:04:14 UTC 2017

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.
> 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

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

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