NTP Advice and Time Fun (Re: Dune Parody skit. Was RE: whitewigs)

[D. Hageman]

I like ddate personally.

Brian, you should code up an adate and submit it to the util-linux people. 
;-)

At any rate - I didn't want this e-mail to be completely fluff, so here is 
some advice.

Non-technical:

Some motherboards have a seriously bad system clock on them.  NTP works by 
slowly skewing the time to keep it in-line with the servers it is feeding 
from.  If your motherboards clock is so bad that NTP believes it can't 
keep up by tiny skews ... then it will give up and stop working.  My 
recommendation for you in this case is have a nightly cron job that stops 
ntpd and calls ntpdate and then starts ntpd again.  You should schedule 
the job at a time when it will least effect the system (i.e. without a lot 
of users or cron jobs dependent on time). In generally doing it on a daily 
basis prevents the skew from being bad enough for it to cause any real 
issues doing this.  My experience is that even the worst system clocks 
will take at least a couple of weeks to get so out of wack before ntp will 
give up.

Technical:

The units of time it works in is called a 'tick' and the actual system 
call used to slowly augment the time is 'adjtimex'.  A smaller unit of 
time exists as well called a 'jiffie'.



On Tue, 22 Mar 2005, Jack wrote:

> Strange, I never had any problems with ntp when I was
> running gentoo. Setting it up in debian was a
> no brainer, and I never have any problems with my time
> being off by very much. Ntp is a great tool to have,
> but it's missing one thing: a plug-in for displaying
> Aztec dates and times.
>
> Brian D.
>
> --- Jonathan Hutchins wrote:
>
>> On Tue, March 22, 2005 4:02 pm, Gerald Combs said:
>>> Jonathan Hutchins wrote:
>>
>>>> Ntp doesn't guarantee correct time, it's just
>> another way to screw it
>>>> up.
>>
>>> It _does_ guarantee that you have the same time as
>> a server or a set of
>>> peers, within a given tolerance.  This is helpful
>> if you want to
>>> correlate log data on different hosts, or run
>> "make" in an NFS-mounted
>>> directory.
>>
>> That's if/when it's configured and working
>> correctly.  Then it'll even
>> provide the correct date for your email timestamps.
>> That's not
>> necessarily a given though.
>>
>> I had a system that ... was six hours off
>> after subsequent reboots.  Gentoo had, in the
>> absence of useful data from
>> the DHCP server, overwritten the valid ntp config
>> file with default
>> garbage.  (This is the default behavior for gentoo.)
>>  Caveat admin.
>>
>
>
>
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//========================================================\\
||  D. Hageman                    <dhageman at dracken.com>  ||
\\========================================================//