Time Sync

[Christopher Ness]

On Tue, 2004-03-02 at 06:16, John Haxby wrote:
> Tom Needs a Hat Mitchell wrote:
> 
> >On Mon, Mar 01, 2004 at 02:15:33PM -0500, Christopher Ness wrote:
> >
> >>You could create a cron job in root and have it run daily.  Here's my
> >>cron entry.  This runs every day at noon, to do this hourly change the
> >>12 to a *.
> >>    
> >>
> >>00 12 * * *  /usr/sbin/ntpdate -u -s -t 20 ntp.cpsc.ucalgary.ca....
> >>    
> >>
> 
> It's not clear to me why you would want to do this when configuring ntpd 
> is so easy -- just run redhat-config-date and check "enable network time 
> protocol".

Won't this stall the machine on boot if a network connection is not
available?  Don't be scared of cron.  It is quite helpful, and if you
have an application that requires all your machines to be somewhat close
in time then is "enable network time protocol" good enough?

I agree with Tom that everyone should randomize their network accesses
though.

> If you want time synchronization on a dial-up connection (where you 
> aren't connected all the time), then there are ntp alternatives that do 
> a good job for that: chrony (http://chrony.sunsite.dk/) for example.   
> Just having npdate change the clock periodically isn't all that good -- 
> note that ntp (and chrony, I expect) use adjtime(2) to speed up or slow 
> down time to keep the clock adjusted.

The above simply fails.  If you do not want to recieve emails from cron
about failures (you probably do, unless you are often not connected to
the network) then redirect the output to /dev/null

The magic of computers.   There are 8x10^6 ways to do something.  Choose
your weapon and stick with it unless something absolutely better comes
by.

Chris
-- 
Software Engineering IV,
McMaster University
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