[CentOS-virt] Time

Thu Jan 3 04:17:51 UTC 2013
SilverTip257 <silvertip257 at gmail.com>

On Wed, Jan 2, 2013 at 7:27 PM, James B. Byrne <byrnejb at harte-lyne.ca>wrote:

>
> > @James:  Can you specifically cite why you manually power down each
> > node? Have you tried tweaking your libvirt settings in the config
> > file I noted in my earlier response to Robert?
>
> Two reasons.  First, I am minimally familiar with kvm. The niceties of
> the options for it is beyond my kin for the nonce.  Second, libvirt
> does not always work.  I have had guests refuse to either suspend or
> shutdown from an automatic request to do so.  When shutdown is done
> manually one discovers right away that there is a problem and which
> guest is causing it.
>
>
I hear ya.  I've never had libvirt not work, but I've had an issue or two
with VMs shortly after they were created (not production at that point).


> > Set up a central NTP server and have your hosts (and not just VMs)
> > connect to it.  It could be the VM host, but doesn't need to be.
> > Distribute the load to your NTP server and off of the public NTP pool
> > by running an NTP server for your servers to poll [0] ... it's a good
> > practice and everybody is happy.
> >
>
> I do that as well.  However, I run one on each host just to serve its
> own guests and configure the host to run off our central ntp server.
>
> >
> >
> >> 4.  On each guest have a cron job that checks for ntpd at regular
> >> intervals which reports failures and restarts the time service as
> >> necessary. We use:
> >>   JOBNAME="Check ntpd status and restart if required" ; \
> >>     ntpstat > /dev/null && \
> >>     if [[ $? -gt 0 ]]; then /sbin/service ntpd start; fi
> >>
> >>
> > Why not configure the ntpd daemon and stick with that?
> > It does update on its own [1]. And ntpstat prints out the interval,
> > which matches the one mentioned at [1].
> > I don't believe the ntpstat script/job is necessary (I've never had to
> > do more than set ntpd to run after configuring the servers it should
> > poll).
> >
>
> You misunderstand the purpose of the job.  Netstat checks to see if
> the daemon is actually running.  If it is not then netstat returns a
> non-zero exit code. If the ntpstat exit code is not zero then the
> service script is invoked to restart it.  Additionally, netstat writes
> out to stderr that it could not find the daemon which gets emailed to
> support. I probably should have used [[ ! $? -eq 0 ]] but what I have
> written does work.
>
> We found ntpd just stoped on some guests upon occasion without any
> visible trace of a cause.  Not frequently but when it did happen it
> was a nuisance to detect before clock drift on the guest caused some
> failure or other.  This job detects these occurrences and self
> corrects.
>
>
I'll have to check my hosts tomorrow and see if there's any drift.
Thanks for the explanation.


> These are all CentOS-6.3 hosts and guests.
>
> --
> ***          E-Mail is NOT a SECURE channel          ***
> James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
> Harte & Lyne Limited          http://www.harte-lyne.ca
> 9 Brockley Drive              vox: +1 905 561 1241
> Hamilton, Ontario             fax: +1 905 561 0757
> Canada  L8E 3C3
>
> _______________________________________________
> CentOS-virt mailing list
> CentOS-virt at centos.org
> http://lists.centos.org/mailman/listinfo/centos-virt
>

-- 
---~~.~~---
Mike
//  SilverTip257  //
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.centos.org/pipermail/centos-virt/attachments/20130102/3c367d13/attachment-0005.html>