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I'm running a RHEL 5 (64 bit) guest on Microsoft Hyper-V.

I've always had trouble with the clock getting way ahead of itself, which I was able to solve previously by adding

divider=10 clocksource=acpi_pm

to the kernel params in /boot/grub/menu.lst and setting up ntpd.

This worked with kernel 2.6.18-194.3.1.el5 however since the security upgrade to 2.6.18-194.8.1.el5 ntp will not longer sync.

Here is the output of ntpq -pn with 2.6.18-194.3.1.el5

$ ntpq -pn
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+192.189.54.33   203.35.83.242    2 u    5   64  377   17.311  -51.753  63.074
*202.83.64.2     203.35.83.242    2 u    7   64  377   19.625  -104.46  27.096
+202.60.94.11    203.12.160.2     3 u   62   64  377   34.398  -121.42  26.216
 127.127.1.0     .LOCL.          10 l   11   64  377    0.000    0.000   0.001

And with 2.6.18-194.8.1.el5

$ ntpq -pn
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 192.189.54.33   192.189.54.17    3 u   28   64   17   17.075  -9505.7 5518.42
 192.189.54.17   203.35.83.242    2 u   28   64   17   17.389  -9669.1 5596.65
 202.60.94.11    203.12.160.2     3 u   33   64   17   33.192  -142.84 9016.50
*127.127.1.0     .LOCL.          10 l   31   64   17    0.000    0.000   0.001

I'm out of ideas. I've tried a few other kernel params such as

notsc divider=10

But still the same results.

Any suggestions on what else may work?

user38939
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2 Answers2

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I believe I have just found the answer. I needed to add in notsc but also keep divider=10 and clocksource=acpi_pm as well.

The entry in /boot/grub/menu.lst now looks like this and the click seems to be synch'ing again:

kernel /vmlinuz-2.6.18-194.8.1.el5 ro root=/dev/VolGroup00/LogVol00 rhgb quiet notsc divider=10 clocksource=acpi_pm
user38939
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Are integration services configured to set the clock? If so have you tried disabling it?

Chris S
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    Hi Chris, Yes I disabled this. Pretty much I have followed the steps in the URL below. This was working perfectly until the upgrade do the new kernel. http://social.technet.microsoft.com/Forums/en-US/winserverhyperv/thread/28c93dc4-3313-4121-8448-fb30c78d0359 – user38939 Jul 15 '10 at 05:27