ntpdate
Jonathan Chen
jonc at chen.org.nz
Wed Nov 16 18:30:09 GMT 2005
On Wed, Nov 16, 2005 at 12:09:45PM -0500, Chuck Swiger wrote:
[...]
> Running "ntpdate -b" at boot to forcibly syncronize the clock is a pretty
> good idea, but you actually can convince ntpd to sync even a clock which is
> badly off via:
>
> -g Normally, ntpd exits if the offset exceeds the sanity limit,
> which is 1000 s by default. If the sanity limit is set to
> zero,
> no sanity checking is performed and any offset is acceptable.
> This option overrides the limit and allows the time to be set
> to
> any value without restriction; however, this can happen only
> once. After that, ntpd will exit if the limit is exceeded.
> This
> option can be used with the -q option.
The advantage of `ntpdate' vs `ntpd -g' is that ntpdate does it
_immediately_, whereas `ntpd -g' takes a bit of time before it decides
which server to sync to. This means that if your clock is out by
hours/days, there will be a period of 3-7 minutes after you boot where
your system time is badly incorrect, and then you have this big skip
when it corrects.
This could be a problem if you've got overanxious users running
`make' and other time sensitive programs almost immediately after boot;
not to mention weird skips in your various log files.
Cheers.
--
Jonathan Chen <jonc at chen.org.nz>
----------------------------------------------------------------------
"If everything's under control, you're going too slow"
- Mario Andretti
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