nanog mailing list archives
Re: NTP Issues Today
From: Damian Menscher <damian () google com>
Date: Tue, 20 Nov 2012 16:59:13 -0800
On Tue, Nov 20, 2012 at 4:49 PM, Jimmy Hess <mysidia () gmail com> wrote:
On 11/19/12, Van Wolfe <vanwolfe () 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 to2012. 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
Current thread:
- Re: NTP Issues Today, (continued)
- Re: NTP Issues Today Jared Mauch (Nov 20)
- Picking outside NTP servers (Re: NTP Issues Today) Jay Ashworth (Nov 20)
- Re: Picking outside NTP servers (Re: NTP Issues Today) George Herbert (Nov 20)
- Re: Picking outside NTP servers (Re: NTP Issues Today) Majdi S. Abbas (Nov 20)
- Re: NTP Issues Today Ask Bjørn Hansen (Nov 21)
- Re: NTP Issues Today Jimmy Hess (Nov 20)
- Re: NTP Issues Today Darius Jahandarie (Nov 20)
- Re: NTP Issues Today Blake Dunlap (Nov 20)
- Re: NTP Issues Today George Herbert (Nov 20)
- Re: NTP Issues Today Robert E. Seastrom (Nov 21)
- Re: NTP Issues Today Darius Jahandarie (Nov 20)
- Re: NTP Issues Today Damian Menscher (Nov 20)
- Re: NTP Issues Today Alvaro Pereira (Nov 20)
- RE: NTP Issues Today Chuck Church (Nov 21)
- Re: NTP Issues Today Greg Ihnen (Nov 21)
- Re: NTP Issues Today Clay Haynes (Nov 19)
- Re: NTP Issues Today Ryan Malayter (Nov 21)
- Re: NTP Issues Today Ryan Malayter (Nov 21)
- Re: NTP Issues Today Neil Harris (Nov 21)