Since the errata kernel release 2.6.18-164.6.1 we have been seeing Xen domU's that will occasionally jump forward in time by 40-80 minutes. the behavior is such that the clock will jump forward and then just sit there until the clock of the underlying dom0 catches up to it again. At first we were running ntpd on our domU's but then disabled it in response to suggestions in several howtos. So now we know that the problem has nothing to do with rogue ntp packets but could very well be something in xen or kernel-xen that is causing it. There's a report of something very similar in the CentOS forum to which I've appended more details of this bug. https://www.centos.org/modules/newbb/viewtopic.php?topic_id=23402 Nothing in the upstream vendor bugzilla about this that I can find, or nothing in the Xen mailing lists that's obvious. Any help is appreciated. Steve Timm -- ------------------------------------------------------------------ Steven C. Timm, Ph.D (630) 840-8525 [log in to unmask] http://home.fnal.gov/~timm/ Fermilab Computing Division, Scientific Computing Facilities, Grid Facilities Department, FermiGrid Services Group, Assistant Group Leader.