schurzi's blog

As you might already know VMWare and time sync are two things that don't play well together. Most times the time is off by some seconds or minutes or even better the time is not synchronized at all. I discovered today that ESXi 3.5 does not enable time sync by default. Even if you installed the VMWare tools!

To enable it, you need to log in into the Guest OS and execute the graphical program to adjust this setting. The program is "vmware-toolbox" and you simply need to activate the option "Time synchronization between the virtual machine and the ESX Server". Quite simple, but to do this you need either a X Server installed in the Guest OS or a forwarded X connection to a Workstation with a X Server. I personally don't like this, because it is complicated and you can't automate it. So I searched for a method to do this in a CLI interface.

After a bit of searching I found the following solution.

# Linux
vmware-guestd --cmd "vmx.set_option synctime 0 1" # Enable
vmware-guestd --cmd "vmx.set_option synctime 1 0" # Disable

# Windows
vmwareservice --cmd "vmx.set_option synctime 0 1" # Enable
vmwareservice --cmd "vmx.set_option synctime 1 0" # Disable

If time sync is already enabled, you will get a error message saying that the previous state is already set.