Am 23.01.2013 um 06:21 schrieb Ron Loftin <reloftin at twcny.rr.com>: > > On Tue, 2013-01-22 at 21:16 -0600, Matt Garman wrote: >> Hi, >> >> We have a little over 100 servers, almost all running CentOS 5.7. >> Virtually all are Dell servers, generally a mix of 1950s, R610s, and >> R410s. >> >> We use NTP and/or PTP to sync their clocks. One phenomenon we've >> noticed is that (1) on reboot, the clocks are all greatly out of sync, >> and (2) if the PTP or NTP process is stopped, the clocks start >> drifting very quickly. >> >> If it was isolated to one or two servers, I'd dismiss the issue. I >> also had this problem under CentOS 4. >> >> I suspect something is mis-configured, because I can't imagine the >> hardware clock on ALL these servers is *that* bad. > > Well -- in my experience ( 15+ years with RH variants of Linux, and ~25 > with various Unix flavors ) they CAN be that bad -- especially with some > of the "economy" chipsets used with the Intel architecture. It gets > worse when you have a CMOS battery that's getting old and weak. The > clock may default back to its initial value, or it might just run slow. > > Some folks might consider this a "brute force" approach, but I keep it > simple and just reset the hardware clock once a week via cron. I prefer > to do it in the wee hours, shortly before the weekly cron jobs run on > Sunday morning. Put something like this in root's crontab. > > 3 3 * * 0 /sbin/hwclock --systohc this is already done in /etc/rc.d/init.d/halt on halt/reboot. -- LF