Isaac Bennetch on 8 Jul 2015 11:40:38 -0700


[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]

Re: [PLUG] ntp


I believe ntpd attempts to compensate for drift; which is great if your system clock is drifting at a consistent rate because of some internal timing error. It's less helpful if you're like me and have a virtual machine (virtualbox in my case) that somehow gets fewer clock cycles when not in the foreground (or heaven forbid you suspend/pause the machine!). If the machine was in the foreground a lot, it would run faster than real speed (with the ntpd drift compensation this could be something like a minute fast per hour) or in the background it could lose time at a shocking rate. In particular, the shock came after running git commit then wondering why I couldn't find the commit at the top of git log :-)

My solution was also to run ntpdate on some schedule, which isn't what I would call production hardened but is good enough for my uses.

There was supposedly a vntp program, for virtual ntp, which was designed to overcome this. For some reason I'm not using it, so it mustn't have worked right or I didn't figure out installation or some such.

Kind regards,
Isaac

> On Jul 8, 2015, at 2:15 PM, Walt Mankowski <waltman@pobox.com> wrote:
> 
> 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" 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 
>> (M) +1.215.432.5167 
>> www.daotechnologies.com 
>> 
>> 
>> From: "Bill East" <wm.east@gmail.com> 
>> To: "Philadelphia Linux User's Group Discussion List" <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 > wrote: 
>> 
>> 
>> 
>> So I just noticed that my KVM server's clocks were way off. The host OS was 4 minutes behind time.gov and the guests were 4 minutes ahead of 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 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! 
>> 
>> ___________________________________________________________________________ 
>> Philadelphia Linux Users Group -- http://www.phillylinux.org 
>> Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce 
>> General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug 
>> 
>> 
>> 
>> 
>> 
>> ___________________________________________________________________________ 
>> Philadelphia Linux Users Group -- http://www.phillylinux.org 
>> Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce 
>> General Discussion -- http://lists.phillylinux.org/mailman/listinfo/plug
> 
>> ___________________________________________________________________________
>> Philadelphia Linux Users Group         --        http://www.phillylinux.org
>> Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
>> General Discussion  --   http://lists.phillylinux.org/mailman/listinfo/plug
> 
> ___________________________________________________________________________
> Philadelphia Linux Users Group         --        http://www.phillylinux.org
> Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
> General Discussion  --   http://lists.phillylinux.org/mailman/listinfo/plug
___________________________________________________________________________
Philadelphia Linux Users Group         --        http://www.phillylinux.org
Announcements - http://lists.phillylinux.org/mailman/listinfo/plug-announce
General Discussion  --   http://lists.phillylinux.org/mailman/listinfo/plug