How to Fix VMware Guest OS Clock Running Too Fast or Too Slow

Problem

VMware guests sometimes display incorrect time, with the clock running faster or slower than real time.

Solution for a fast clock

Install VMware Tools.

Enable time synchronization in the guest OS.

Edit the GRUB kernel line to add clock=pit. Example for Fedora Core:

title Fedora Core (2.6.9-1.667)
root (hd0,0)
kernel /vmlinuz-2.6.9-1.667 ro root=/dev/hda2 clock=pit

If VMware Tools cannot be installed or the guest is SuSE SLES9, replace clock=pit with clock=pmtmr.

Solution for a slow clock

Install VMware Tools.

Enable time synchronization.

If the guest is a single‑CPU VM, add nosmp noapic nolapic to the kernel parameters. Example for Red Hat Linux:

title Red Hat Linux (2.4.20-28.9)
root (hd0,0)
kernel /vmlinuz-2.4.20-28.9 ro root=/dev/hda2 clock=pit nosmp noapic nolapic

The steps are based on VMware’s knowledge‑base article “Clock in a Linux Guest Runs More Slowly or Quickly Than Real Time” (Doc ID: 1420). The full article can be consulted at https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1420.

In environments where the guest OS can access the Internet, running an NTP client inside the guest and synchronizing with external time servers provides precise time keeping.