Cacti EZ: System time / clock is running out of sync in virtual machine

If you are running a Cacti EZ based on CentOS 4.x inside a Hyper V Virtual Machine you will see that the machines system time runs out of sync, but you have configured NTP correctly.

Symtoms:

• If Cacti EZ runs for about one hour and you may see a time difference of ~90 seconds to your NTP time.
• "ntpdate -u ntp.example.com" command shows you differences to the current time whenever you execute it.

Solution:

• Append clock=pit as kernel boot parameter to /boot/grub/menu.lst as documented in The system time runs too fast on a Linux-based virtual machine

title CentOS (2.6.9-100.EL.plus.c4smp)
	root (hd0,0)
	kernel /vmlinuz-2.6.9-100.EL.plus.c4smp ro root=LABEL=/ clock=pit
	initrd /initrd-2.6.9-100.EL.plus.c4smp.img