VMWare

Configuration File (.vmx) and time variables

posted Jun 8, 2011, 9:35 AM by Darren Ash

Sometimes some VMWare images that are used for testing or training may need to start with a specific date time and you may not want it to update based on the system clock.  This can be accomplished by adding the following items to the VM configuration file.

To Disable Time Synchronization Completely:
If you want to keep a fictitious time in a virtual machine, so that the clock in the guest is never synchronized with that on the host, you must disable time synchronization completely.
A virtual machine occasionally synchronizes time with the host even if you do not turn on periodic time synchronization. To completely disable time synchronization, you must set some properties in the virtual machine configuration file.

Prerequisites
Power off the virtual machine.
Procedure
1  Open the configuration (.vmx) file of the virtual machine with a text editor. 

2  Add lines for the time synchronization properties and set the properties to FALSE. 

tools.syncTime = "FALSE"
time.synchronize.continue = "FALSE"
time.synchronize.restore = "FALSE"
time.synchronize.resume.disk = "FALSE"
time.synchronize.shrink = "FALSE"
time.synchronize.tools.startup = "FALSE"

3  Save and close the file.


If you want to set the date - time to a specific value you can set the real time clock for the VM by setting the variable "rtc.startTime" equal to the number of seconds elapsed from since Jan 1, 1970 00:00 UTC.  So, to set clock to 7/1/2010 8:50AM UTC you would assign the variable in the .vmx file to be:

 rtc.startTime=1277974200



For more details see the Timekeeping document from VMWare attached below.  Also attached is a simple Excel spreadsheet with an embedded VB function to calculate the seconds offset for you.

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