Easing clock to correct time via ntp

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2 total messages Started by J.B. Nicholson-Owens Wed, 02 Sep 1992 18:11

#913

Author: J.B. Nicholson-Owens
Date: Wed, 02 Sep 1992 18:11

22 lines
1567 bytes

I've heard that using a simple "ntp -s" or "ntp -f" isn't good for the  
system because the clock might jump to the correct time from whatever it  
was set at before and cause a crontab entry to be skipped.

I don't know if this is true and, therefore, was wondering if it would be  
a good idea to stick an "ntp -s <ntp host>" in as a crontab entry running  
every 10 minutes?   I figure the worst that will happen with this is that  
the clock will be set correctly the first time and never be too far off  
from what time it *really* is.  Unfortunately, if my clock isn't that  
good, it will only be correct on the 10th minute, when it was jerked to  
the correct time.

If there is a way to ease the clock forward or backward (accelerate or  
decelerate the ticking of seconds, I suppose) so that the clock was  
correct relatively all the time and not pass up any minutes or seconds  
(thus solving any problem with crontab entries being skipped), how is that  
done?

Thanks.
--
-- Jeff (jeffo@uiuc.edu)
-- no NeXTmail please

Re: Easing clock to correct time via ntp

#931

Author: Louis A. Mamakos
Date: Wed, 02 Sep 1992 23:35

28 lines
1889 bytes

In article <BtyqJ7.9vo@news.cso.uiuc.edu> jeffo@uiuc.edu (J.B. Nicholson-Owens) writes:
>I've heard that using a simple "ntp -s" or "ntp -f" isn't good for the  
>system because the clock might jump to the correct time from whatever it  
>was set at before and cause a crontab entry to be skipped.

Yes, this is true.  Its generally pretty rude to just reset the clock
while stuff is running.

>If there is a way to ease the clock forward or backward (accelerate or  
>decelerate the ticking of seconds, I suppose) so that the clock was  
>correct relatively all the time and not pass up any minutes or seconds  
>(thus solving any problem with crontab entries being skipped), how is that  
>done?

You could just run ntpd all the time.  It will constantly correct the
clock while and even estimate the intrinsic drift of the clock
hardware and continue to apply corrections to compenstate even when
the network is unavailable.  

NeXT even thoughtfully provides a hacked version of the NTP software
written by Mike Petry and myself at the University of Maryland.  If
you are serious about time synchronization, you should dump that
version and bring up xntp3 which is the latest and greatest.  It
compiles and runs on a NeXT with no problems, though it doesn't do
anything with netinfo, so you'll have to build an /etc/ntp.conf file
instead.  This is a feature, not a bug.

louie

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