Correcting time drift with CentOS on Hyper-V
I was having trouble with the clock in my Linux Hyper-V VM’s.The time was constantly drifting forward. Using NTP only slowed the drift a bit down but often NTP gave up after several days.
I tried a lot of NTP configurations, but basically the local clock was just unreliable. Even using rdate every 10 minutes was already showing backwards jumps of several seconds. As one of my VM’s is running dovecot this really was a problem because dovecot hates time moving backwards.
I finally found the solution posted by Mat Mirabito in his blogpost “Linux (specifically CentOS running trixbox) gains excessive time on system clock”.
Edit your grub.conf and add the following to the kernel line:
divider=10 clocksource=acpi_pm
After this it works like… clockwork 
Thanks for the entry, helped me with my 2 virtual DNS in Hyper-V
I’m glad I could help
It took me a year before finding a solution and I hope this post will prevent others from having such a long frustrating time.
I added like below but now solved.
title CentOS (2.6.18-164.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-164.el5 ro root=/dev/VolGroup00/LogVol00
initrd /initrd-2.6.18-164.el5.img
divider=10 clocksource=acpi_pm
is it correct?
@Ken Kim:
No, the divider part should be added on the end of the line starting with “kernel”.
title CentOS (2.6.18-164.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-164.el5 ro root=/dev/VolGroup00/LogVol00 divider=10 clocksource=acpi_pm
initrd /initrd-2.6.18-164.el5.img