[ntp:questions] Re: ntp sanity limit kills ntp daily

Unruh unruh-spam at physics.ubc.ca
Fri May 20 22:49:25 UTC 2005

Michael Ward <michaelward at sprintmail.com> writes:

>Hello All,

>I've configured my FC3 system to run ntp successfully at boot time and 
>ntp seems to run successfully for about a day.  However, every night the 
>clock looses some 1200 seconds while the system is busy making backups. 
>  When ntp figures this out, it refuses to update the clock because this 
>is classified as insane, and terminates.

>I happen to agree that the clock loosing about 1200 seconds (for any 
>reason) seems insane.  However, given that this sort of behavior seems 
>common enough to be found via google (search for: ntp exceeds sanity 
>limit), I'm hopeful that there is a way to coax ntp (or some other 
>automated program) to trudge on and do the deed anyway.

>Default rules can make is seem like a crazy world, can't they?

>I'm running a self compiled linux kernel 2.6.9 with FC3 linux as 
>installed from Negus' "Red Hat Fedora Linux 3".  Anyoune out there know 
>how to make this sort of thing work in a rational manner?

One of the configuration parameters I believe is how much the time can be
out befor it is considered insane. I know it exists in chrony, and believe
it also exists on ntp.

(eg on chrony it is the parameter maxupdateskew)

However you probably also want to figure out why backups are destroying
your clock. Somehow the timer interrupt is being ignored. You may have set
the priority on disk interrups too high somehow.

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