[CentOS] NTP and virtual guests

[Stephen Harris]

On Mon, May 28, 2012 at 08:41:30AM -0400, James B. Byrne wrote:
> We encountered a problem with respect to KVM virtual host restore and
> NTP. Specifically, our VM test host was shutdown by an extended power
> outage and when power returned all of the restored guests were
> immediately shutdown by ntp because the time differential between the
> restored systems and that of the ntpd sync servers exceeded the panic
> threshold.

Umm, ntp won't shut down your guests unless you've done something
non-standard.  NTP inside the guest will abort because of the time
difference but the guest will keep running... just with the wrong time.

See the "-g" option:

       -g      Normally, ntpd exits with a message to the system  log  if  the
               offset exceeds the panic threshold, which is 1000 s by default.
               This option allows the time to be  set  to  any  value  without
               restriction; however, this can happen only once. If the thresh-
               old is exceeded after that, ntpd will exit with  a  message  to
               the  system  log.  This  option  can be used with the -q and -x
               options. See the tinker command for other options.

-- 

rgds
Stephen