system clock is too slow

[Rick Stevens]

Jorge Fábregas wrote:
> On Tuesday 27 July 2004 7:20 pm, Rick Stevens wrote:
> 
>>ntpdate drags your machine kicking and screaming into compliance with
>>your NTP servers RIGHT NOW, while ntpd KEEPS it current.  If ntpd has to
>>pull the machine into compliance, it does it just a little bit at a time
>>so it may take quite a while for it to get it synchronized.  Once the
>>clock is synched, ntpd will keep it synched.
> 
> 
> Wow! Thanks for that wonderful explanation Rick. Now I understand it.  I'll 
> definetely run ntpdate at boot and will run ntpd as a daemon!
> 
> Thanks Rick and Ben!

You're welcome.  Ben's comment about ntpd slewing the clock is correct.
ntpdate essentially does a "date" command using the data from the
NTP server.  The clock jumps from what it was to the correct time.
This may cause cron jobs to be missed if they fell in the gap.  ntpd
slews through, no more than a minute at a time, so the cron jobs will
run.

In my experience, cron jobs missed due to an ntpdate jump aren't a big
issue, but it depends on what you have set up.  The system-critical cron
jobs run via anacron and will run OK since anacron's philosophy isn't so
much that "it's 10:00, run this job", it's more like "oh, 10:00 has
passed...let's do what didn't get done."
----------------------------------------------------------------------
- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
- grasshopotomaus: A creature that can leap to tremendous heights... -
-                                                ...once.            -
----------------------------------------------------------------------