NTP Issues Today

Wed Nov 21 00:59:13 UTC 2012

On Tue, Nov 20, 2012 at 4:49 PM, Jimmy Hess <mysidia at gmail.com> wrote:

> On 11/19/12, Van Wolfe <vanwolfe at gmail.com> wrote:
> > Did anyone else experience issues with NTP today?  We had our server
> > times update to the year 2000 at around 3:30 MT, then revert back to
> 2012.
>
> Are you sure that you are actually using NTP to set your clock?
> For you to sync with 2000,  you should have had multiple confused
> peers from multiple time sources;  possibly a false radio signal....
>
> NTP by default has a panic threshold of 1000 seconds.
>
> This  _should_   have caused NTP to execute a panic shutdown,
> instead of setting the clock back  30 million seconds.
>

>From logs various people have posted, it appears NTPd saw the excessive
time shift and took the reasonable(?) step of killing itself.  The OS
detected ntpd's death and took the reasonable step of restarting it.  On
startup, ntpd can be reasonably(?) configured with the -g option to bypass
the 1000s limit to set the starting time before going into the regular ntpd
time adjustment code.

In this case that would have set them back to 2000....

It's a good lesson on how a chain of reasonable decisions can lead to a bad
outcome, so you really need to understand the interactions of the whole
system.

Damian