Re: [PLUG] ntp

["Keith C. Perry" <kperry@daotechnologies.com>]

Right but to me that is still better than continuing to drift because a workload prevented accurate time keeping.

I think someone mentioned this already.  This probably needs to be configurable for either case- either keep the time on track absolutely or keep the 1000s (or some other configurable tolerance).  Be able to notify if an absolute snap back is over a certain tolerance or if you will NOT snap the time back because of a tolerance exceeded respectively.

Maybe this is already available?

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 
Keith C. Perry, MS E.E. 
Owner, DAO Technologies LLC 
(O) +1.215.525.4165 x2033 
(M) +1.215.432.5167 
www.daotechnologies.com

----- Original Message -----
From: "JP Vossen" <jp@jpsdomain.org>
To: "Philadelphia Linux User's Group Discussion List" <plug@lists.phillylinux.org>
Sent: Wednesday, July 8, 2015 2:47:15 PM
Subject: Re: [PLUG] ntp

Right, sudden jumps in time are BAD, and that's exactly what running
`ntpdate` from cron does...  :-)

On 07/08/2015 02:44 PM, Josh Zenker wrote:
> The reason for this behavior, if I remember correctly, is to avoid
> breaking certain applications which do not gracefully handle sudden
> changes to the system clock.
> 
> About 2 years ago I worked, briefly, with some systems using ntp.  Turns
> out if the time is off by some small amount (less than a minute IIRC),
> it simply stops changing the target system's time because it "thinks"
> something is drastically wrong.
> 
> Seems like a cron job to re-sync is a good idea to me.
> 
> Eric
> 
> On Wed, Jul 8, 2015 at 2:24 PM, Keith C. Perry
> <kperry@daotechnologies.com <mailto:kperry@daotechnologies.com>> wrote:
> 
>     I hope you're saying that in jest Walt.  In my experience ntpd slips
>     way too much.  Once clocks get out of sync by too much ntpd won't
>     nudge it back and that can happens more often than not on
>     interactive and poorly tuned HPC nodes.
> 
>     You can have the same issue on system boots.
> 
>     My apologies if I'm misinterpreting tone.
> 
>     ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
>     Keith C. Perry, MS E.E.
>     Owner, DAO Technologies LLC
>     (O) +1.215.525.4165 x2033 <tel:%2B1.215.525.4165%20x2033>
>     (M) +1.215.432.5167 <tel:%2B1.215.432.5167>
>     www.daotechnologies.com <http://www.daotechnologies.com>
> 
>     ----- Original Message -----
>     From: "Walt Mankowski" <waltman@pobox.com <mailto:waltman@pobox.com>>
>     To: plug@lists.phillylinux.org <mailto:plug@lists.phillylinux.org>
>     Sent: Wednesday, July 8, 2015 2:15:39 PM
>     Subject: Re: [PLUG] ntp
> 
>     But...but...
> 
>     You do realize that's essentially what ntpd does, only ntpd does it
>     way better, right?
> 
>     Right?
> 
>     On Wed, Jul 08, 2015 at 01:37:59PM -0400, Keith C. Perry wrote:
>     > That's what I do. Run "ntpdate us.pool.ntp.org
>     <http://us.pool.ntp.org>" every 4 to 6 hours on critical / core systems.
>     >
>     >
>     > ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
>     > Keith C. Perry, MS E.E.
>     > Owner, DAO Technologies LLC
>     > (O) +1.215.525.4165 x2033 <tel:%2B1.215.525.4165%20x2033>
>     > (M) +1.215.432.5167 <tel:%2B1.215.432.5167>
>     > www.daotechnologies.com <http://www.daotechnologies.com>
>     >
>     >
>     > From: "Bill East" <wm.east@gmail.com <mailto:wm.east@gmail.com>>
>     > To: "Philadelphia Linux User's Group Discussion List"
>     <plug@lists.phillylinux.org <mailto:plug@lists.phillylinux.org>>
>     > Sent: Wednesday, July 8, 2015 1:35:29 PM
>     > Subject: Re: [PLUG] ntp
>     >
>     >
>     >
>     > I just had to deal with a vendor installation which was about 4
>     seconds off the ntp server it was supposed to be synced with. Come
>     to find out the vendor ran a ntpdate command once a day and the vm
>     was drifting 4 seconds in the 24 hours between. Their solution was
>     to run the command once an hour instead.
>     > On Jul 8, 2015 1:13 PM, "Eric Riese" < eric.riese@gmail.com
>     <mailto:eric.riese@gmail.com> > wrote:
>     >
>     >
>     >
>     > So I just noticed that my KVM server's clocks were way off. The
>     host OS was 4 minutes behind time.gov <http://time.gov> and the
>     guests were 4 minutes ahead of time.gov <http://time.gov> .
>     >
>     > Turns out the host did not have ntp installed at all. It's Ubuntu
>     12.04 and was installed as some sort of minimal installation. A sudo
>     apt-get install ntp and five minutes later it's in good shape.
>     >
>     > The guests are debian installs from turnkeylinux.org
>     <http://turnkeylinux.org> and they have ntp installed but were not
>     running by default!
>     >
>     > To think, Google runs it's own internal NTP servers and had to
>     spread the leap second out over a day, and I'm off by whole minutes!

Later,
JP
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JP Vossen, CISSP            |:::======|      http://bashcookbook.com/
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