Re: NTP problem for virtual RHEL 4 server on VmWare

Interesting observation. Our troublesome VM has been running for quite a log
while, though, and it still seems quite unstable. We just rebooted it with
the kernel parameters mentioned in (thank
you Mr. Dill), and I'll post the results back here in a day or two.
Hopefully it will solve our problem, even thogh it didn't solve yours.

What puzzles me is why this VM drifts so much, while most of our other VMs
doens't (at least not more than NTPd can handle).

On 11/12/08, Eric Sisler <lbylnxgek@xxxxxxxxx> wrote:

On Fri, Nov 7, 2008 at 2:49 AM, Kenneth Holter <kenneho.ndu@xxxxxxxxx


One of our RHEL 4 servers running on VmWare has a quite serious NTP
I know that NTP can be an issue when running red hat boxes on VmWare, so
a fix I put this small script in a file in /etc/cron.hourly:

Early on I went through the frustrations with time & NTP problems on RHEL 4
virtual machines. I've used a number of the earlier suggestions, including
various boot time & VMware configuration options. I even went so far as
compile a custom kernel with the clock frequency set back to 100, as it was
for the 2.4.x kernels. Overall it didn't seem like any of the boot time or
VMware config options made that much difference. Recompling the kernel
works, but gets to be a lot of overhead after awhile.

Now for the odd part: Currently my RHEL4 VMs have time sync enabled in the
VMware config file & also have NTP running. It seems that the longer NTP
runs, the more accurate the time gets on the VM. When booting a "new" VM,
it wasn't uncommon for NTP to adjust the time by 20-30 seconds. Once the
gets a bit "older" & NTP has been running longer, when rebooting the VM
clock adjustment goes down to around 5-6 seconds. I suspect part of this
has to do with the frequency & adjustment history recorded by NTP.

The updated VMware KB may be of some help as well. Good luck!

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